Endocannabinoid-dependent protection against kainic acid-induced long-term alteration of brain oscillations in guinea pigs

Brain Research 1661 (2017) 1–14

Contents lists available at ScienceDirect

Brain Research journal homepage: www.elsevier.com/locate/bres

Research report

Endocannabinoid-dependent protection against kainic acid-induced long-term alteration of brain oscillations in guinea pigs Liubov Shubina a,⇑, Rubin Aliev b,c, Valentina Kitchigina a,d a Laboratory of Systemic Organization of Neurons, Institute of Theoretical and Experimental Biophysics of Russian Academy of Sciences, 3 Institutskaya Str., Pushchino, Moscow Region 142290, Russian Federation b Laboratory of Biophysics of Active Media, Institute of Theoretical and Experimental Biophysics of Russian Academy of Sciences, 3 Institutskaya Str., Pushchino, Moscow Region 142290, Russian Federation c Computer Science Department, Moscow Institute of Physics and Technology, 9 Institutskiy Per., Dolgoprudny, Moscow Region 141700, Russian Federation d Department of Biophysics and Biomedicine, Pushchino State Institute of Natural Sciences, 3 Nauki Pr., Pushchino, Moscow Region 142290, Russian Federation

a r t i c l e

i n f o

Article history: Received 30 August 2016 Received in revised form 2 February 2017 Accepted 3 February 2017 Available online 10 February 2017 Keywords: AM404 URB597 Medial septum Hippocampus Entorhinal cortex Amygdala

a b s t r a c t Changes in rhythmic activity can serve as early biomarkers of pathological alterations, but it remains unclear how different types of rhythmic activity are altered during neurodegenerative processes. Glutamatergic neurotoxicity, evoked by kainic acid (KA), causes hyperexcitation and acute seizures that result in delayed brain damage. We employed wide frequency range (0.1–300 Hz) local field potential recordings in guinea pigs to study the oscillatory activity of the hippocampus, entorhinal cortex, medial septum, and amygdala in healthy animals for three months after KA introduction. To clarify whether the activation of endocannabinoid (eCB) system can influence toxic KA action, AM404, an eCB reuptake inhibitor, and URB597, an inhibitor of fatty acid amide hydrolase, were applied. The cannabinoid CB1 receptor antagonist AM251 was also tested. Coadministration of AM404 or URB597 with KA reduced acute behavioral seizures, but electrographic seizures were still registered. During the three months following KA injection, various trends in the oscillatory activities were observed, including an increase in activity power at all frequency bands in the hippocampus and a progressive long-term decrease in the medial septum. In the KA- and KA/AM251-treated animals, disturbances of the oscillatory activities were accompanied by cell loss in the dorsal hippocampus and mossy fiber sprouting in the dentate gyrus. Injections of AM404 or URB597 softened alterations in electrical activity of the brain and prevented hippocampal neuron loss and synaptic reorganization. Our results demonstrate the protective potential of the eCB system during excitotoxic influences. Ó 2017 Elsevier B.V. All rights reserved.

1. Introduction Oscillations in rhythmic brain activity arise from the synchronized activity of neurons and are thought to play an essential role in information processing (Vinogradova, 1995; Buzsáki, 2006). Oscillation disturbances in vulnerable brain areas can serve as early indexes of pathological changes (Bragin et al., 2002; Salami et al., 2014; Dümpelmann et al., 2015). However, it remains unclear how different types of oscillations are altered during neurodegenerative processes.

Abbreviations: 2-AG, 2-arachidonoyl glycerol; BA, basal nucleus of the amygdala; eCBs, endocannabinoids; FAAH, fatty acid amide hydrolase; HFO, high frequency oscillations; KA, kainic acid; LFP, local field potential; MS, medial septum; SE, status epilepticus. ⇑ Corresponding author. E-mail address: [email protected] (L. Shubina). http://dx.doi.org/10.1016/j.brainres.2017.02.003 0006-8993/Ó 2017 Elsevier B.V. All rights reserved.

Glutamatergic excitotoxicity is one of the factors leading to the development of neurodegeneration. It was discovered that an intra-brain injection of kainic acid (KA), a potent analog of glutamate, induces behavioral seizures and neuropathological lesions, which can be exploited in animal models of epilepsy (Ben-Ari et al., 1979). Unfortunately, seizure pathology often resists pharmacological therapy (Mazarati et al., 1998; Mayer et al., 2002). One of the prospective seizure-modifying approaches is activation of the endocannabinoid system as a natural homeostatic regulator (for review see Kano et al., 2009). This system includes the cannabinoid Gi/o-coupled (inhibition of adenylyl cyclase and Ca2+ channels, activation of K+ channels) CB1 and CB2 receptors, their endogenous ligands (endocannabinoids, hereafter referred to as eCBs), and the associated enzymes participating in synthesis, transport and degradation of these ligands. Synthesis of eCBs from membrane precursors is carried out ‘‘on demand” depending on current brain activity. Two known eCBs, anandamide and 2-arachidonoyl glycerol

2

L. Shubina et al. / Brain Research 1661 (2017) 1–14

(2-AG) are greatly elevated in response to a variety of pathological events (Panikashvili et al., 2001; Marsicano et al., 2003; van der Stelt et al., 2006). eCBs mostly act as retrograde messengers and, upon their release from postsynaptic neurons, modulate neurotransmitter release via activation of presynaptic cannabinoid receptors (for review see Kano et al., 2009).

Despite the abundance of work clarifying the role of eCB in the regulation of acute seizures (Wallace et al., 2001, 2002, 2003; Shafaroodi et al., 2004; Karanian et al., 2005, 2007; Bahremand et al., 2008; Coomber et al., 2008; Naderi et al., 2008, 2011; Kozan et al., 2009; Mason and Cheer, 2009; Rizzo et al., 2009; Naidoo et al., 2011, 2012; Shubina and Kichigina, 2012; Citraro

Fig. 1. Experimental design. (A) Scheme of electrode and guide cannula arrangement and their positioning according to Rapisarda and Bacchelli (1977). Recording electrodes were positioned in the medial septum (MS), basal nucleus of the amygdala (BA), CA1 field of the hippocampus (Hip) and entorhinal cortex (Ent), whereas the guide cannula for microinjections was implanted above the right lateral brain ventricle (LV) contralaterally to the recording electrodes. (B) Depiction of areas for neuronal quantification shown in the Nissl-stained coronal slice of dorsal hippocampus. Squares mark the counting frames in the CA1, CA3a, CA3b and hilus. (C) Schematic protocol of the experiment. Following the baseline LFP recordings and single injections of the substances used (DMSO, AM404, URB597 or AM251), KA was coadministered with vehicle (DMSO) or cannabinoid-related compounds (AM404, URB597 or AM251) and animals were continuously monitored for 5–6 h. After KA administration, daily injections of vehicle (DMSO) or cannabinoid-related compounds (AM404 or URB597) were made for 7 days and LFP recordings were performed weekly for 3 months.

L. Shubina et al. / Brain Research 1661 (2017) 1–14

et al., 2013; Vilela et al., 2013; Shubina et al., 2015), scant evidence exists for an influence of cannabinoid-related drugs in the more remote changes after excitotoxic events (Ma et al., 2014; Di Maio et al., 2015; Suleymanova et al., 2016). Neurodegenerative changes in seizure pathologies often reside in mesial temporal lobe structures such as the hippocampus where cell loss is most prominent. The entorhinal cortex, amygdala and medial septal region (MS), which have connections with the hippocampus and each other (Alonso and Kohler, 1984; Calderazzo et al., 1996; Cenquizca and Swanson, 2007; Colom, 2006; Dudley et al., 1990; Leranth et al., 1999; Meibach and Siegel, 1977; Pitkänen et al., 1997; Risold and Swanson, 1997; Sah et al., 2003; van Groen et al., 2003), also suffer cell damage under pathological conditions (including KA-induced neurotoxicity) (Buckmaster and Dudek, 1997a,b; Carriero et al., 2012; Covolan et al., 2000; Cronin et al., 1992; Drexel et al., 2011, 2012; Du et al., 1995; Franck, 1984; Fritsch et al., 2009; Garrido-Sanabria et al., 2006; Gordon et al., 2015; Kumar and Buckmaster, 2006; Levesque and Avoli, 2013; Nadler, 1981; Pitkänen et al., 1998; Scholl et al., 2013; Sloviter et al., 2006; Tuunanen et al., 1996; Wenzel et al., 2000).

3

The main aim of the present work is to shed light on the question of whether suppression of eCB transport and degradation with AM404 and URB597 will protect the brain against KA-induced excitotoxicity and influent the oscillatory activity in the brain. To achieve reliable effects, the eCB-related drugs were injected before convulsant administration, during KA-evoked seizures, and one week after the insult. This approach can help to understand how the eCB system works generally in the excitotoxic conditions and how it prevents longer-term consequences of excitotoxicity. In this regard, we assess the degree of injury and subsequent axonal reorganization in the hippocampal formation and changes in the brain oscillations after KA injection alone, and injection together with eCB-related drugs. 2. Results 2.1. Oscillations in the background activities of the hippocampus, medial septum, entorhinal cortex and amygdala Local field potentials (LFPs) of guinea pigs in a state of quiet wakefulness included oscillations at various frequency bands

Fig. 2. Baseline activity and KA-induced seizure event in the medial septum (MS), hippocampus (Hip), entorhinal cortex (Ent) and basal nucleus of the amygdala (BA). (A, B) Representative LFPs and (C, D) respective spectrograms in 0.1–200 Hz and 0.1–40 Hz frequency ranges showing the short-time Fourier transform of the activity before (C) and after the KA injection (D).

4

L. Shubina et al. / Brain Research 1661 (2017) 1–14

usually below 0.4 mV in amplitude (0.25 ± 0.08 mV) (Fig. 2A). Activity was registered from 0.1 to 300 Hz, but in each recorded structure the expression at various frequency bands was not equal. Thus, activity amplitude in the hippocampus (field CA1) was higher in a wider range of frequencies (0.1–250 Hz) than in other studied structures (0.1–150 Hz for the entorhinal cortex and 0.1– 100 Hz for MS and basal amygdala, BA) (Fig. 2A, C). Expression of oscillations in various frequency bands also varied between the structures (Fig. 2A, C). In the BA, a spindle-shaped alpha rhythm was sometimes observed, which was not typical for other structures. 2.2. Brain oscillations disturbances after kainic acid injection and the influences of endocannabinoid-related drugs Unilateral i.c.v. microinjection of KA induced prominent convulsive status epilepticus (SE) lasting several hours (Shubina et al., 2015). Repeated epileptiform discharge clusters (seizure events) were observed in all recorded brain structures (Figs. 2B, D; S1). As we have shown earlier, coadministration of AM404 or URB597 with KA attenuated SE. In contrast, CB1 antagonist AM251 at the dose applied was not able to modify KA-induced SE (Shubina et al., 2015). Electrographic seizures were registered in all experimental groups regardless of substance co-administrated with KA (Fig. S1). In the present study, which is the continuation of the work mentioned above, we analyzed the changes in oscillatory activity of the investigated brain structures at different frequency bands for three months after the KA-induced episode of neurotoxicity. It should be stressed that although co-administration of AM404 or URB597 with KA significantly alleviated KA-induced SE by decreasing behavioral manifestations, electrographic seizures were recorded in both groups (Fig. S1). The spectral analysis revealed a variety of changes in LFP power in the recorded brain areas during the three months after KA administration (‘‘KA/Vehicle” group). In this case, a considerable long-term decrease in LFP power was observed in the MS. These alterations were progressive: within a month after KA injection a significant decrease in LFP power was observed only for the theta frequency range, whereas after three months the same changes were revealed in almost all frequency bands (Fig. 3 ‘‘KA/Vehicle”; % change from background LFP power (n = 68), 3rd month (n = 15): delta, 88 ± 19, p = 0.013; theta, 82 ± 17, p < 0.0001; alpha, 81 ± 14, p < 0.0001; beta, 90 ± 18, p = 0.04; high-frequency oscillations, HFO, 87 ± 26, p = 0.024; Tables S1, S2). No long-term decreases in LFP power at different frequency ranges in the MS were observed in the groups with cannabinoid-related compound administration (‘‘KA/AM404”, ‘‘KA/URB597”, ‘‘KA/AM251”, Table S2). Moreover, in these groups an increase in LFP power in the certain frequency ranges was observed (Fig. 3, Table S2). The only exception was the high-frequency range of the ‘‘KA/AM404” group in which LFP power decreased. In the hippocampus a power of electrical activity in frequency ranges under investigation changed differently after the injection of KA. One month after KA administration, the LFP power of all studied frequency bands increased significantly (Fig. 3 ‘‘KA/Vehicle”;% change from the background LFP power (n = 64), 1st month (n = 22): delta, 132 ± 23, p < 0.0001; theta, 142 ± 22, p < 0.0001; alpha, 140 ± 26, p < 0.0001; beta, 140 ± 24, p < 0.0001; gamma, 175 ± 42, p < 0.0001; HFO, 139 ± 45, p < 0.0001; Tables S1, S3). LFP power then returned to the background values except for the delta oscillations (Fig. 3 ‘‘KA/Vehicle”; % change from the background LFP power (n = 64), 3rd month (n = 15): delta, 136 ± 23, p < 0.0001; Table S3). Administration of cannabinoid-related compounds (groups ‘‘KA/AM404”, ‘‘KA/URB597”, and ‘‘KA/AM251”) prevented these LFP power change dynamics (Table S3). Although

an increase in LFP power in a wide frequency range was observed in the ‘‘KA/AM404” group, it was more gradual (Fig. 3; Table S3). For the gamma and HFO frequency ranges, only the ‘‘KA/AM251” group displayed a significant increase in LFP power for all three months after KA injection (Fig. 3; % change from background LFP power (n = 59), 1st month (n = 19): gamma, 114 ± 13, p = 0.031; HFO, 126 ± 25, p < 0.0001; 2nd month (n = 18): gamma, 133 ± 42, p = 0.001; 3rd month (n = 20): gamma, 123 ± 23, p < 0.0001; HFO, 126 ± 9, p < 0.0001; Table S3). Changes in the rhythmic activity of the entorhinal cortex after KA administration differed from the other structures. Three months after excitotoxin introduction, there was essentially no change in oscillatory activity in the ‘‘KA/Vehicle” or ‘‘KA/AM251” groups. At the same time, significant increases in LFP power at a majority of investigated frequency bands were observed in the ‘‘KA/AM404” and ‘‘KA/URB597” groups (Fig. 3; Table S4). Oscillations in the BA within three months post KA administration changed most nonuniformly. As a general trend, LFP power decreased in all experimental groups except the ‘‘KA/AM404” (Fig. 3; Table S5). However, the dynamics of this decrease varied between groups. In the ‘‘KA/Vehicle” and ‘‘KA/AM251” groups, the decrease in LFP power was preceded by an increase, whereas in the ‘‘KA/URB597” group LFP power decreased and then remained at the background level (Fig. 3; Table S5). Maximum LFP power increment in the ‘‘KA/AM404” group was observed two months after KA injection, and levels returned to almost initial values by the end of the third month. An increase in LFP power was also revealed for the HFO range of the ‘‘KA/Vehicle” group and in the gamma frequency range of the ‘‘KA/AM251” group (Fig. 3; Table S5). We did not find any significant changes in LFP power at different frequency bands in the investigated brain structures of control sham-operated animals for the three months after the surgery (Fig. S2). 2.3. Morphological alterations in the dorsal hippocampus after kainic acid neurotoxicity and the influences of endocannabinoid-related drugs 2.3.1. Cell loss in the hippocampus Three months after KA administration, considerable alteration of the dorsal hippocampus was revealed. The greatest damage was found in the CA3a field in the ‘‘KA/Vehicle” and ‘‘KA/AM251” groups (Fig. 4A, D). Here, degradation of the pyramidal layer reached 71% and 63% vs. ‘‘Control” (the hippocampus of health animals) for the ‘‘KA/Vehicle” and ‘‘KA/AM251” groups respectively (Fig. 4A, D; cell density: 1345 ± 359 in the ‘‘Control” (n = 17) to 388 ± 337 in the ‘‘KA/Vehicle” (n = 16), p < 0.0001, and to 492 ± 362 in the ‘‘KA/AM251” (n = 14), p < 0.0001; Table S6). In these groups, the amount of cells in the hilus of the dentate gyrus was also considerably reduced (especially in the right hippocampus): the neuron loss was 31% for the ‘‘KA/Vehicle” group and 35% for the ‘‘KA/AM251” group (Fig. 4A, B; cell density in the right hippocampus: 822 ± 105 in the ‘‘Control” (n = 16) to 564 ± 117 in the ‘‘KA/Vehicle” (n = 18), p < 0.0001, and to 535 ± 143 in the ‘‘KA/AM251” (n = 18), p < 0.0001; cell density in the left hippocampus: 832 ± 121 in the ‘‘Control” (n = 16) to 655 ± 93 in the ‘‘KA/Vehicle” (n = 18), p = 0.0002, and to 552 ± 130 in the ‘‘KA/AM251” (n = 20), p < 0.0001; Table S6). Interestingly, if blockers of eCB inactivation were used (‘‘KA/AM404” or ‘‘KA/URB597” groups), no damages were observed in either the CA3a field, or in the hilus of the dentate gyrus, and thus the density of cells in these areas did not differ from the values of control animals (Fig. 4A, B, D; Table S6). In the CA3b fields of the left and right hippocampus, neuronal loss varied depending on the experimental group. In the

L. Shubina et al. / Brain Research 1661 (2017) 1–14

5

Fig. 3. Change of the LFP power of the medial septum (MS), hippocampus (Hip), entorhinal cortex (Ent) and basal nucleus of the amygdala (BA) during three months after the coadministration of KA with DMSO (KA/Vehicle) or cannabinoid-related drugs (KA/AM251, KA/AM404 and KA/URB597). The percent of change relative to the background activity (100%) is coded by the color (*p < 0.05, vs. background values; Kruskal-Wallis test followed by Dunn’s post-hoc test).

‘‘KA/URB597” and ‘‘KA/AM404” groups, the decrease in cell numbers compared to the ‘‘Control” group was insignificant, whereas it reached around 30% in the ‘‘KA/AM251” group and around 40% in the ‘‘KA/Vehicle” group (Fig. 4C; cell density in the right hippocampus: 418 ± 85 in the ‘‘Control” (n = 15) to 246 ± 42 in the

‘‘KA/Vehicle” (n = 17), p < 0.0001, and to 291 ± 53 in the ‘‘KA/ AM251” (n = 18), p = 0.0002; cell density in the left hippocampus: 391 ± 99 in the ‘‘Control” (n = 16) to 236 ± 35 in the ‘‘KA/Vehicle” (n = 18), p = 0.0004, and to 268 ± 52 in the ‘‘KA/AM251” (n = 20), p < 0.0001; Table S6).

6

L. Shubina et al. / Brain Research 1661 (2017) 1–14

Fig. 4. Nissl-stained sections and quantitative analysis of the cell density of the dorsal hippocampus. Three months after KA administration, neuronal loss is found in the hilus (A, B) of the dentate gyruse and fields CA3a (A, D), CA3b (C) and CA1 (E) of the ‘‘KA/vehicle” and ‘‘KA/AM251” groups. (*p < 0.001 vs. ‘‘Control” group, #p < 0.05 vs. ‘‘KA/Vehicle” group, Mann-Whitney test U with Bonferroni correction). In the ‘‘KA/AM404” and ‘‘KA/URB597”, a partial preservation of neurons in the hilus of the dentate gyruse (A, B) and fields CA3a (A, D), CA3b (C) and CA1 (E) is revealed.

In the ‘‘KA/Vehicle” group, cell density decreased in the CA1 field of the dorsal hippocampus by 48% and 36% for the left and right hippocampus respectively (cell density in the right hippocampus: 507 ± 76 in the ‘‘Control” (n = 19) to 324 ± 98 in the ‘‘KA/Vehicle” (n = 19), p < 0.0001; cell density in the left hippocampus: 560 ± 101 in the ‘‘Control” (n = 16) to 291 ± 48 in the

‘‘KA/Vehicle” (n = 18), p < 0.0001; Table S6). Similar but less prominent changes were induced by coadministration of KA and AM251 (28% and 22% decrease for the left and right hippocampus respectively; cell density in the right hippocampus: 507 ± 76 in the ‘‘Control” (n = 19) to 393 ± 68 in the ‘‘KA/AM251” (n = 19), p = 0.0006; cell density in the left hippocampus: 560 ± 101 in the

L. Shubina et al. / Brain Research 1661 (2017) 1–14

7

Fig. 5. Sections of the dorsal hippocampus stained by the Timm method for identification of mossy fiber sprouting in the dentate gyrus. These sections demonstrate Timmnegative stain (A) from a control animal without any injection, (C) from the KA/AM404- and (D) KA/URB597-treated animals. Timm-positive stain in the dentate inner molecular layer is revealed in the (B)‘‘KA/Vehicle” and (E)‘‘KA/AM251” groups.

‘‘Control” (n = 16) to 402 ± 84 in the ‘‘KA/AM251” (n = 20), p = 0.0002; Table S6). Importantly, in the ‘‘KA/AM404” and ‘‘KA/ URB597” groups such disturbances were not observed and the densities of cells in the CA1 field of the left and right hippocampus did not differ from the values of control animals, which had not received any injections (Fig. 4E; Table S6). 2.3.2. Detection of the mossy fiber sprouting Three months after KA administration, mossy fiber sprouting in the inner molecular layer of the dentate gyrus was revealed in the ‘‘KA/Vehicle” group as well as in the ‘‘KA/AM251” group (Fig. 5B, E). As with the control group, no sprouting of mossy fibers were observed at this time point in the groups where the blockers of eCB inactivation were applied (‘‘KA/AM404” and ‘‘KA/URB597” groups) (Fig. 5A, C, D). 3. Discussion In the model of KA-induced excitotoxicity we showed that activation of the eCB system before and after neurotoxic event decreases disturbances in the oscillatory activity in several brain areas and alleviates hippocampal damage. It was also demonstrated that inhibition of the eCB system did not have this impact. In the present study we used enhanced cannabinoid signaling that is believed to be a more subtle physiological way of activating the eCB system (‘‘on demand”). 3.1. Histological and electrophysiological changes following neurotoxicity Earlier we showed that co-administration of KA and AM404 or URB597 alleviated KA-induced SE, decreasing behavioral manifestations and duration of electrographic seizures (Shubina et al.,

2015). Nevertheless, in most of these cases the electrographic seizures developed in all investigated structures and lasted no less than three hours, indicating the presence of excitotoxicity. It is possible that the application of cannabinoid-related drugs prevented excessive excitation and suppressed the distribution of seizure activity to motor cortices or the brain stem, which blocked convulsive behavior. In the present study, three months after KA injection, neuronal death was observed throughout the dorsal hippocampus (fields CA1 and CA3). In the CA3a field, almost a full reduction of the pyramidal cell layer was detected in the right dorsal (septal part) hippocampus, and the number of cells decreased in both hippocampi. These results corroborate the data obtained earlier in similar neurotoxic models, where the CA3 field was also found to be the most vulnerable area in the hippocampus (for review see Levesque and Avoli, 2013). Such vulnerability of the CA3 field can be explained by the highest expression level of various types of kainic receptor subunits (GluK2, GluK4, GluK5) in this area (Carta et al., 2014). We also have found a significant reduction of neuronal density in the CA1 fields of the right and left hippocampus. Similar alterations were revealed previously by other groups (Franck, 1984; Buckmaster and Dudek, 1997a; Carriero et al., 2012). One can hypothesize that neurodegeneration in the CA3 field could cause subsequent neuronal death in the CA1 field (Gordon et al., 2015). Besides the hippocampus, in the present work we also found a decrease in neuron density in the hilus of the dentate gyrus. Earlier studies have observed a similar decrease several months after KA introduction (Nadler, 1981; Cronin et al., 1992; Buckmaster and Dudek, 1997a,b; Wenzel et al., 2000; Sloviter et al., 2006). It is important to note that the dentate gyrus is a critical gate-acting node in the temporal lobe seizure network (Sloviter et al., 2006; Krook-Magnuson et al., 2015), and that the decrease in cells number in the hilus of the dentate gyrus is consid-

8

L. Shubina et al. / Brain Research 1661 (2017) 1–14

ered to be one of the markers of pathology (Nadler, 1981; Cronin et al., 1992; Buckmaster and Dudek, 1997a,b; Wenzel et al., 2000; Sloviter et al., 2006). In our study, we also found sprouting of mossy fibers in the inner third of the dentate gyrus molecular layer three months after KA administration. This result, which agrees with data obtained in similar models with KA administration (Cronin et al., 1992; Buckmaster and Dudek, 1997a; Wenzel et al., 2000; Shao and Dudek, 2005), points to the creation of a recurrent exciting network in the hippocampus, which can promote seizures (Tauck and Nadler, 1985; Dudek and Shao, 2004). A variety of factors may affect the brain electrical activity during neuropathological conditions. For example, deletion of calcium-binding protein S100B reduced gamma oscillations during KA-induced seizure conditions (Sakatani et al., 2007). The histopathology in the hippocampus, which we found as a result of toxic KA influences, may be an anatomical substrate of the LFP disturbances observed over the course of three months. Within a month after KA injection, we found a significant increase in activity power in the hippocampal CA1 field at all frequency bands. However, two months later, the activity returned to background values with the exception of the delta rhythm. We can not explain exactly the reasons of these changes, but we speculate that the elevation of LFP power in CA1 can be evoked by an increase in excitability and/ or synchronization of pyramidal cell activity. Prominent neurodegeneration in the CA3 field observed in the present work could cause the lack of CA1 interneuron excitation. Moreover, a reduction in inhibition efficiency could be caused by the significant loss of specific groups of GABAergic interneurons in CA1 (Best et al., 1993, 1994; Morin et al., 1998). According to these facts, a substantial decrease of inhibition in the CA1 field is seen one month after KA-induced SE (Ashwood and Wheal, 1986; Cornish and Wheal, 1989; Meier et al., 1992). It has also been shown that during pathological processes the CA1 pyramidal neurons, as well as granular cells, can form excitation back projections to themselves (axonal sprouting) (Meier and Dudek, 1996; Perez et al., 1996; Esclapez et al., 1999; Smith and Dudek, 2001, 2002; Shao and Dudek, 2004). It is interesting to note that in the first month after SE induced by another neurotoxin pilocarpine, an enhancement of the persistent sodium current was observed in the CA1 field of the hippocampus which then slowly decreased over time (Chen et al., 2011). It was shown that the persistent sodium current contributes to the elevation of neuronal excitability and bursting behavior (Stafstrom, 2007). Spontaneously discharging bursting neurons might contribute to the formation of hypersynchronization in epilepsy (Szilágyi et al., 2014). Besides, an increase of excitement in the hippocampus can be promoted by the reorganization of the neuronal networks, forming new excitatory synapses on granular and pyramidal cells as a result of sprouting in the dentate gyrus and CA3 field. Another factor, which possibly contributes to disturbances in hippocampal activity, is the change in CB1 receptor expression after administration of convulsants. Depending on the phase of pathology development, downregulation or upregulation of CB1 receptor expression pattern can occur (Karlócai et al., 2011). The possibility of an increase in CB1 receptor expression on the GABAergic terminals in the CA1 field and dentate gyrus causing a weakening of inhibitory control of hippocampal pyramidal cell activity can not be ruled out (Maglóczky et al., 2010; Karlócai et al., 2011). On the other hand, increases of CB1 receptor number in the CA1 and CA3 fields (Wallace et al., 2003) as well as in the newly formed Timm-positive mossy fiber terminals (Bhaskaran and Smith, 2010) can decrease neuronal excitability. The ‘‘normalization” of hippocampal electrical activity (except the delta rhythm), revealed in the present study two months after KA injection, could be also promoted by the partial restoration of inhibition via sprouting of the surviving interneurons and the

increase in their activity (Davenport et al., 1990; Maglóczky and Freund, 2005). Contrary to the results of the present study, there are several lines of evidence which have shown a decrease of theta power in the hippocampus in temporal lobe epilepsy models (Arabadzisz et al., 2005; Colom et al., 2006; Dugladze et al., 2007; Chauvière et al., 2009; Kitchigina and Butuzova, 2009; Marcelin et al., 2009; Sinel’nikova & Kitchigina, 2011; Astasheva et al., 2015) and in the MS (Sinel’nikova and Kichigina, 2011; Kitchigina et al., 2013; Astasheva et al., 2015). The use of different experimental paradigms, animal species, location of the recording electrodes, or the period of LFP registration may explain this discrepancy. In the present work, we found a decrease in LFP power in the theta frequency range in the MS a month after KA injection. This was opposite to the change of these oscillations in the hippocampus. It is interesting that this decrease was progressive and enveloped almost all studied frequency ranges three months after SE induction. It can be explained by disorganization/desynchroniza tion of neuronal activity in the MS as a result of the death of a considerable proportion of GABAergic septal neurons (Colom et al., 2006; Garrido-Sanabria et al., 2006) and disturbances in intraseptal inhibitory control of MS activity (Malkov and Popova, 2011). Alteration of the MS rhythmogenesis in turn can affect the formation of synchronization in the hippocampus, which is a crucial process in the genesis of seizure activity. Opposing changes of the LFP power in the hippocampus and MS during the three months after KA administration (an increase and decrease, respectively) can reflect processes of pathological synchronization (in the hippocampus) or desynchronization (in the MS), and can indirectly indicate a functioning mismatch of these structures. In agreement with our study, it has been shown earlier that the correlation of LFPs of the hippocampus and MS decreased during epileptogenesis (Popova et al., 2008; Astasheva et al., 2015). In the basal nucleus of the amygdala, we found a decrease in LFP power two months after KA infusion. One possible reason for these changes could be the death of somatostatin-containing interneurons in the basal and lateral nuclei of amygdala (Tuunanen et al., 1996; Pitkänen et al., 1998). Moreover, it can be hypothesized that disturbance of GABAergic system functioning in the MS as the consequence of seizure pathology (Colom et al., 2006; GarridoSanabria et al., 2006) can reduce its inhibitory control of the ‘‘striatal” amygdala, which in turn can increase inhibition of the ‘‘cortical” amygdala. The increase of LFP power after KA-induced neurotoxicity in the delta frequency range of the hippocampus and BA found in the present study could probably result from the enhancement of synchronization in the thalamocortical system and could reflect the pathological process. Surprisingly, the entorhinal cortex was the only structure in which we did not find any changes in LFP power during the three months after KA administration. It is possible that changes in the electrical activity of the entorhinal cortex can occur in the first weeks or more than three months after the excitotoxic influence of KA. Thus, we propose that here we did not ‘‘catch” the changes of LFP power in this structure although long-term morphological alterations have been observed earlier in the entorhinal cortex after inducing SE by KA (Du et al., 1995; Drexel et al., 2011, 2012) or pilocarpine (Du et al., 1995; Kumar and Buckmaster, 2006). 3.2. Influences of the eCB system on histological and electrophysiological changes caused by kainic acid-induced excitotoxicity In this study, we used eCB inactivation blockers to explore their efficacy in preventing chronic KA-evoked alterations. We revealed

L. Shubina et al. / Brain Research 1661 (2017) 1–14

that injection of AM404 (an eCB reuptake inhibitor) or URB597 (an eCB degradation enzyme inhibitor) along with the KA influence considerably reduced KA-induced damages in the brain. Three months after KA injection, the number of cells in the CA1 and CA3 hippocampal fields and in the hilus of the dentate gyrus in these groups was not reduced comparative to the control. We believe that the prolongation of eCB functioning mediates the decrease of neuronal excitability that can promote preservation of cells. This is in line with the observation that a post-SE single injection of CB1 receptor agonist WIN 55.212-2 promoted cell survival in the hilus of the dentate gyrus five months after pilocarpine-induced SE (Suleymanova et al., 2016). The exact mechanisms by which the eCB system protects neurons during excitotoxic events are yet unknown, though an abundance of studies have proposed different factors in cell protection. Among them are the activation of immediate early genes (O’Donovan et al., 1999; Zhang et al., 2002; Marsicano et al., 2003; Wettschureck et al., 2006), neurotrophic factors (Zhang et al., 2002; Marsicano et al., 2003; Xu et al., 2003; Khaspekov et al., 2004; Hammonds et al., 2007), the ability to regulate cell metabolism (Bénard et al., 2012) and neurogenesis (Palazuelos et al., 2006; Aguado et al., 2007), anti-inflammatory and antioxidative effects (Polascheck et al., 2010; Di Maio et al., 2015). Here, we also did not find any sprouting of mossy fibers in the dentate gyrus three months after KA-induced seizures if URB597 or AM404 were infused. It was shown that damaging influences could cause the strengthening of neurogenesis, contributing to aberrant reorganization of hippocampal communications during seizures (Parent et al., 1997). In this light, our results are in keeping with previous findings that the FAAH blocker URB597 reduces neurogenesis caused by amygdalar kindling (Wendt et al., 2011). The preservation of neuronal populations three months after KA injection in the ‘‘KA/AM404” and ‘‘KA/URB597” groups could promote safety of electrical activity of the investigated brain structures. Namely, in the hippocampus no significant increases in rhythms were found in the first month after KA administration. Although an increase in LFP power was observed in the animals with AM404 infusion, it was gradual, less expressed and did not include oscillations higher than 80 Hz. In addition, one month after KA infusion in the ‘‘KA/AM404” and ‘‘KA/URB597” groups, we were unable to see any substantial increase in hippocampal HFO, which is supposed to be one of the markers of epileptogenesis (Staba et al., 2014). We hypothesize that the first month after toxic KA influence is a critical period for the development of pathological activity. Any decrease of excitability or prevention of hypersynchronization during this period, which could be achieved by blocking eCB inactivation, may dampen development of further disturbances. Thus, in the MS we would not have seen progressive alterations of the oscillatory activity if the blockers of eCBs inactivation were infused (groups ‘‘KA/AM404” and ‘‘KA/URB597”). In these groups the changes in LFP power in the hippocampus and MS were unidirectional despite the existence of some exceptions. This fact may indirectly demonstrate the maintenance of a coordinated functioning of these structures by the activated eCB system. In the amygdala, the injection of AM404 or URB597 also softened KA-induced changes of LFP power. Thus, in the ‘‘KA/URB597” group, after a short reduction of LFP power in the majority of frequency bands, activity returned nearly to the background. As for the increase of oscillation power in the ‘‘KA/AM404” group, its maximum was observed only two months after introduction of KA and also returned to nearly initial values at the end of the third month. Unexpectedly, in the entorhinal cortex we observed a significant increase in power of the oscillatory activity within three months after KA injection in the ‘‘KA/AM404” and ‘‘KA/URB597” groups, while this phenomenon did not occur in the ‘‘KA/Vehicle”

9

and ‘‘KA/AM251” groups. One could hypothesize that eCB activation during excitotoxic KA action can promote the survival of basket interneurons, which are the central elements for generation of rhythmic activity (Ylinen et al., 1995; Wang and Buzsáki, 1996). Moreover, preservation of entorhinal control of hippocampal activity in turn can contribute to the survival of pyramidal neurons in the CA1 field and subiculum, projecting back to the entorhinal cortex and influencing its activity. It may be suggested that the beneficial effects of eCB metabolism inhibitors observed here are mediated via anandamide: earlier it have been shown that anandamide but not 2-AG level elevated after moderate brain injury or exposure to KA (Hansen et al., 2001; Marsicano et al., 2003; Lourenço et al., 2011; Naidoo et al., 2011). Further studies are necessary to dissect more precisely the involvement of different eCBs in protection against neurotoxicity. Another picture of changes in LFP power in the brain structures was observed when CB1 receptor antagonist AM251 was injected together with KA. In the dorsal hippocampus three months after KA infusion the power of oscillations greater than 80 Hz was elevated. This is a testament to the development of the pathological focus in this structure (Staba et al., 2014). Lack of other LFP power changes in the rest of the structures can be explained by the overpowering influences of KA itself on the oscillations in the other frequency bands. To attempt to reveal these alterations, a subthreshold dose of KA could be used. The role of CB1 antagonists and eCB system modulators in the development of excitotoxic alteration is still elusive. Although it is generally accepted that CB1 antagonists promote seizure occurrence (Wallace et al., 2002, 2003; Marsicano et al., 2003; Khaspekov et al., 2004; Shafaroodi et al., 2004; Monory et al., 2006; Deshpande et al., 2007; Braakman et al., 2009; Kozan et al., 2009; van Rijn et al., 2011; Vinogradova et al., 2011; Citraro et al., 2013), several studies indicate that CB1 receptor antagonists can also have some anti-epileptogenic features (Chen et al., 2007; Echegoyen et al., 2009). There are only a few experimental studies devoted to the investigation of the eCB system’s influence on the chronic alterations under neutopathological conditions (Ma et al., 2014; Di Maio et al., 2015; Vinogradova and van Rijn, 2015; Suleymanova et al., 2016). In good agreement with our study, direct activation of CB1 receptors by WIN55.212-2 during the first 15 days after pilocarpine-induced SE not only decreased severity, frequency and duration of spontaneous seizures, but also prevented the loss of GABAergic neurons one month after SE. Moreover, six months after the SE, overexpression of NMDA receptor subunits and the development of chronic oxidative damage in the dentate gyrus were reduced (Di Maio et al., 2015). A single post-SE injection of WIN55.212-2 did not affect the long-term increase in seizure susceptibility in the same neuropathological conditions, although it reduced the incidence of early seizures, animal mortality and cell loss in the hilus of the dentate gyrus (Suleymanova et al., 2016). In light of these facts, we can hypothesize that the eCB system affects the development of hyperexcitable networks. We can state that in the KA model of neurotoxicity, the blockers of eCB inactivation AM404 and URB597 interfered with the excitotoxic action of KA, alleviating alterations in the oscillatory activity of the investigated brain structures and prevented the morphological reorganization and cell loss in the hippocampus. Instead, CB1 receptor antagonist AM251 has not revealed any protective effect. Undoubtedly, the weakening of excitotoxic KA influences can be explained by the partial suppression of KA effects on SE expression as a result of increased eCB system activity along KA action. Thus, we can approve only that enhanced eCB signaling counteracts KAinduced prolonged excitotoxic influences. Undoubtedly, further studies are still necessary to improve our understanding of eCB system roles during excitotoxic events.

10

L. Shubina et al. / Brain Research 1661 (2017) 1–14

4. Conclusions Here we showed that activation of the eCB system could attenuate some long-term pathological consequences of KA-induced excitotoxicity. We demonstrated that blocking the eCB reuptake with AM404 and inhibiting the anandamide degradation enzyme (FAAH) with URB597 prevented alterations in hippocampal structure and decreased disturbances in the brain oscillatory activity provoked by excitotoxin injection. It was also shown that inhibition of the eCB system did not have this protective impact. In future investigations we propose to clarify the mechanism of protective eCB actions under KA-induced excitotoxicity. Namely, it is necessary to determine what stage of impacts on eCB system (precondition, during seizures, postcondition) is most effective. We believe that the protective eCB action against KA influences on brain activity detected in our study point out the therapeutic potential of the eCB system in the treatment of brain pathologies induced by neurotoxic injury. 5. Experimental procedure 5.1. Animals and surgery Experiments were performed in young adult guinea pigs (440– 620 g, N = 23) obtained from the Experimental Animal Center of the Institute of Theoretical and Experimental Biophysics (Pushchino, Russia). Animals were housed in pairs with food and water ad libitum. All animal experimentations were approved by the Institutional Bioethics Committee of the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences following guidelines that are in accordance with the Directive (2010/63/EU) of the European Parliament and of the Council. All efforts were made to minimize the number of animals used and their suffering. One week before experiments, animals were exposed to a neurosurgical operation under general anesthesia (18 mg/kg Zoletil plus 12 mg/kg xylazine, i.m.). Guinea pigs were placed in a stereotaxis frame adapted with guinea pig cheekbone bars. Body temperature was maintained with a heating pad, and the cardiopulmonary state was monitored during the surgery with a pulse oximeter (Oxy9Vet Plus, Bionet, South Korea). Depth recording electrodes (insulated nichrome, 0.1 mm diameter) were implanted unilaterally into the medial septum (MS, AP = 12.2, ML = 2, DV = 7.5, angle 15°), CA1 field of the hippocampus (AP = 6.6, ML = 3, DV = 5), entorhinal cortex (AP = 4.6, ML = 5.5, DV = 10.5) and basal nucleus of the amygdala (BA, AP = 10.2, ML = 5, DV = 12.2) according to Rapisarda and Bacchelli (1977) (Fig. 1A). A reference screw electrode was placed into the bone above the cerebellum. A guide cannula for microinjections (stainless steel, 21 gauge) was implanted above the right lateral brain ventricle contralaterally to the recording electrodes (AP = 8.6, ML = 2.5, DV = 1.7) (Fig. 1A). The entire assembly was fixed to the skull with dental acrylic resin. Animals were allowed to recover for one week, during which they were handled and placed into the recording chamber daily for 4–6 days before the experiments were started. 5.2. Induction of neurotoxicity The studies were conducted applying the kainic acid-induced neurotoxicity. To induce the onset of SE, waking guinea pigs were injected with KA (0.4 lg, 0.6 mg/ml, i.c.v.) and continuously monitored for electrographic seizures for 5–6 h following the KA injection. During the electrical recording, behavior of the animals was controlled visually and monitored with a video-system. To identify KA-induced SE, the modified Racine Scale (Racine, 1972) adapted

for guinea pigs (Shubina et al., 2015) was used. Stages 4–5 (tonic-clonic seizures, anticlockwise exploration with postural loss and falling) were identified as developed SE. 5.3. Drugs and drug administration The endocannabinoid reuptake inhibitor N-(4-hydroxyphenyl)arachidonamide (AM404, 15.82 mg/ml), selective fatty acid amide hydrolase (FAAH) inhibitor, [3-(3-carbamoylphenyl)phenyl] Ncyclohexylcarbamate (URB597, 0.81 mg/ml), and selective CB1 receptor antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-di chlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251, 62 mg/ml), all dissolved in DMSO, were used throughout the study. KA dissolved in normal saline (0.6 mg/ml) was administered to induce SE. All drugs were obtained from Sigma Aldrich (St. Louis, MO, USA), dissolved and frozen ( 20 °C) in 10 ll aliquots before the experiments. All injections were made intracerebroventricularly by a Hamilton microsyringe type 75 N with infusion rate 1 ll/min through the guide cannula in waking guinea pigs. Injection usually was started 1 min after microsyringe insertion for brain adaptation. The injection needle was slowly pulled out of the brain 2 min after the drug administration to avoid outflow. Following basal LFP recording, guinea pigs were treated with cannabinoid-related compounds to determine their influence on the background activities of brain structures under investigation. Separate groups of guinea pigs were injected with AM404 (47.46 lg; n = 6), URB597 (1.62 lg; n > 5), AM251 (11.1 lg; n = 5) or vehicle (DMSO, 2 ll; n = 7) (Fig. 1C). The doses of cannabinoidrelated compounds were based on data from the literature exploring these compounds in animal models of epilepsy (Karanian et al., 2005; Manna and Umathe, 2012) and from our preliminary experiments. On the 4th or 5th day after administration of the cannabinoidrelated compounds, the animals were injected with KA. Five minutes before and 1.5 h after the administration of KA, each guinea pig received i.c.v. of either AM404 (47.46 lg), URB597 (1.62 lg), AM251 (11.1 lg) or vehicle (DMSO, 2 ll). Beginning 24 h after KA administration animals received a daily i.c.v. dose of either AM404 (31.64 lg), URB597 (0.81 lg), or vehicle (DMSO, 1 ll) for 7 days (Fig. 1C). 5.4. Local field potential recordings and analysis LFPs were recorded in waking guinea pigs during the daytime between 10 a.m. and 6 p.m. Animals were placed into the recording chamber five minutes before the each session. Signals were preamplified (LMC7101, one per each channel, Nacional Semiconductor, USA), amplified (Grass Instruments, Model 12 Neurodata Acquisition System, USA) and filtered on-line (low-pass at 300 Hz, highpass at 0.1 Hz, with 50 Hz notch filter). Data were digitized (PCIDAS 1200JR, 16 Ch. 12-bit A/D resolution 330 kHz, USA; sampling rate 1000 Hz) and recorded using Datapac 2k2 software (Run Technologies, USA) for off-line analysis. Four channels were recorded simultaneously. Behavior of the animals was controlled visually, and only the periods of motionless state were taken for the analysis. One week after surgery, baseline LFPs were recorded for 3– 4 days, 30–60 min per day. In the experiments with drugs administrations, LFP recording was performed for 10 min before and 30– 60 min after the drug injection. After the KA administration, electrical activity of investigated brain structures was registered continuously during 5–6 h. Thereafter, LFP recordings were carried out weekly for three months after the KA administration (Fig. 1C). At the end of the electrophysiological experiments, Nissl and Timm staining were performed.

L. Shubina et al. / Brain Research 1661 (2017) 1–14

Data were analyzed off-line with the help of custom software in MatLab 8.0 (Mathworks Inc., USA). Artifacts due to animal movements were discarded prior to the analysis. All records of electrical activity were split into 10 min epochs and detrended. Power spectra were computed with the aid of Fourier transform using Welch’s method (Hann window with 4096 samples segment size, 50% overlap between segments). We estimated cumulative sums of LFP amplitudes in certain frequency ranges (delta: 0.5–4 Hz; theta: 4–8; alpha: 8–12; beta: 12–40; gamma: 80–120; HFO: 120– 300 Hz). To illustrate the background activity and prominent electrographic seizures after the KA administration, we calculate spectrograms with a short-time Fourier transform of the raw samples (Hann window, 2048 samples segment size, 50% overlap between segments). To analyze the data we used sets of 10-min epochs of LFP recordings from each animal at the following states: 1) background activity, 4–6 epochs per day, 3–4 days; 2) activity on the 30th, 60th and 90th day after the KA administration, 3–5 epochs per each time-point. For each animal these recordings were compared with their own background (before the KA administration) and the percentage of change was computed. These values were collected and averaged for each experimental group. The number of 10 min epochs of LFP used to analysis is given in the Supplementary table (Table S1). 5.5. Histology Three months after the KA injection, the animals and their agedmatched controls (group ‘‘Control”, n = 4) were processed for Timm and Nissl staining. Briefly, guinea pigs were deeply anesthetized with an overdose of pentobarbital (80 mg/kg, i.p.), injected with 0.35 ml heparin into the heart, and intracardially perfused with 0.37% sodium sulfide in Timm buffer (0.12 M NaH2PO4*2H2O, 0.10 M NaOH, 0.18 mM CaCl2, pH 7.4) for 20 min (15 ml/min). This was followed by cold 4% paraformaldehyde in Timm buffer for 20 min (15 ml/min). Brains were removed from the skull and postfixed overnight in 4% paraformaldehyde in Timm buffer at 4 °C. After cryoprotection in a gradient of sucrose (10% and 20% sucrose in Timm buffer at 4 °C for 24 h each) brains were rapidly frozen in the vapor phase of liquid nitrogen. Coronal sections (15 lm) were cut with cryostat at -19 °C (Thermo Shandon Cryotome E, Thermo Scientific, USA) and collected on poly-L-lysine coated slides for subsequent Nissl and Timm staining. Nissl staining was used to verify electrode and cannula placements (Fig. S3) and to detect cell injury in the dorsal hippocampus. Slide-mounted sections were dried at room temperature overnight, submerged in bi-distilled water with acetate buffer for 5 min and stained in fresh 0.1% cresyl violet for 5–8 min until the desired depth of staining was achieved. To visualize supragranular mossy fiber sprouting in the dentate gyrus, Timm staining of 8–10 sections from each animal (2 slides) was performed in the levels corresponding to AP = 6.4–6.8 of the Rapisarda and Bacchelli (1977) atlas. Slide-mounted sections were developed using the following solution: 60 ml of 50% gum arabic, 7.3 ml of citrate buffer (2.55 g sodium citrate, 2.35 g citric acid), 30 ml of 5.9% hydroquinone, and 0.5 ml of 17% silver nitrate. The physical development was performed in the dark at 26 °C for 60– 90 min. Washing the slides in tap water for 10–15 min terminated development of stain. The stained slides were dehydrated through graded ethanols, cleared in xylene, and coverslipped with Eukitt (Fluka, Germany) mounting medium. Bright field images were acquired on a Leica DM6000B microscope (Leica Microsystems, Germany) with a Leica DFC490 camera. All tissue sections were photographed under identical conditions. In the Nissl-stained sections, neuronal quantification was carried out in the dentate hilus (counting frame 300  300 lm) and

11

hippocampal pyramidal cell layers (fields CA3a, CA3b and CAl; counting frame 500  500 lm) (Fig. 1B). Counts were performed for hilus, CA1 and CA3b in both the left and right hippocampus at levels corresponding to AP = 6.4–6.8 and for CA3a in the right hippocampus in the levels corresponding to AP = 7–7.4 (CA3a) of the Rapisarda and Bacchelli (1977) atlas. For both levels, at least four different sections were evaluated from each animal. Cell quantifications were carried out manually using the ‘‘Cell counter” plugin of the ImageJ software (1.50i, USA) by an investigator who was blind to experimental group. 5.6. Statistics Results are presented as mean ± standard deviation. All statistical tests were performed using SPSS Statistics software (version 21, IBM Corp., USA). Changes in LFP power of different frequency bands were tested in two steps: statistically significant results by the Kruskal-Wallis test were analyzed by the Dunn’s post-hoc test. In this case the number of samples (n) referred to the total number of 10-min records of LFP used to analysis. Cell numbers in the different areas of the hippocampus from the control and drug-treated groups were compared by a similar two-step statistical procedure with a post hoc analysis done by the Mann-Whitney U test assuming a Bonferroni correction for multiple pairwise comparisons with the control group. In this analysis the number of samples (n) represented the total number of brain slices used to perform quantification of cells. Non-parametric statistics were used to avoid assumptions about either homogeneity of variances or normality of distributions. All tests used were two-sided; p < 0.05 was considered statistically significant. Conflict of interest statement Nothing declared. Acknowledgments This work was supported by the Russian Foundation for Basic Research (grant numbers 14-44-03607, 15-04-05463, 16-3400457) and by a Grant of the President of the Russian Federation (‘‘Leading scientific schools” 850.2012.4). The authors are grateful to Catherine Chamberlin for comments and help in preparing the manuscript. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.brainres.2017.02. 003. References Aguado, T., Romero, E., Monory, K., Palazuelos, J., Sendtner, M., Marsicano, G., Lutz, B., Guzmán, M., Galve-Roperh, I., 2007. The CB1 cannabinoid receptor mediates excitotoxicity-induced neural progenitor proliferation and neurogenesis. J. Biol. Chem. 282, 23892–23898. Alonso, A., Kohler, C., 1984. A study of the reciprocal connections between the septum and entorhinal area using anterograde and retrograde axonal transport methods in the rat brain. J. Comp. Neurol. 225, 327–343. Arabadzisz, D., Antal, K., Parpan, F., Emri, Z., Fritschy, J.M., 2005. Epileptogenesis and chronic seizures in a mouse model of temporal lobe epilepsy are associated with distinct EEG patterns and selective neurochemical alterations in the contralateral hippocampus. Exp. Neurol. 194, 76–90. Ashwood, T.J., Wheal, H.V., 1986. Loss of inhibition in the CA1 region of the kainic acid lesioned hippocampus is not associated with changes in postsynaptic responses to GABA. Brain Res. 367, 390–394. Astasheva, E., Astashev, M., Kitchigina, V., 2015. Changes in the behavior and oscillatory activity in cortical and subcortical brain structures induced by

12

L. Shubina et al. / Brain Research 1661 (2017) 1–14

repeated L-glutamate injections to the medial septal area in guinea pigs. Epilepsy Res. 109, 134–145. Bahremand, A., Shafaroodi, H., Ghasemi, M., Nasrabady, S.E., Gholizadeh, S., Dehpour, A.R., 2008. The cannabinoid anticonvulsant effect on pentylenetetrazole-induced seizure is potentiated by ultra-low dose naltrexone in mice. Epilepsy Res. 81, 44–51. Bénard, G., Massa, F., Puente, N., Lourenço, J., Bellocchio, L., Soria-Gómez, E., Matias, I., Delamarre, A., Metna-Laurent, M., Cannich, A., Hebert-Chatelain, E., Mulle, C., Ortega-Gutiérrez, S., Martín-Fontecha, M., Klugmann, M., Guggenhuber, S., Lutz, B., Gertsch, J., Chaouloff, F., López-Rodríguez, M.L., Grandes, P., Rossignol, R., Marsicano, G., 2012. Mitochondrial CB1 receptors regulate neuronal energy metabolism. Nat. Neurosci. 15, 558–564. Ben-Ari, Y., Lagowska, J., Tremblay, E., Le Gal La Salle, G., 1979. A new model of focal status epilepticus: intra-amygdaloid application of kainic acid elicits repetitive secondarily generalized convulsive seizures. Brain Res. 163, 176–179. Best, N., Mitchell, J., Baimbridge, K.G., Wheal, H.V., 1993. Changes in parvalbuminimmunoreactive neurons in the rat hippocampus following a kainic acid lesion. Neurosci. Lett. 155, 1–6. Best, N., Mitchell, J., Wheal, H.V., 1994. Ultrastructure of parvalbuminimmunoreactive neurons in the CA1 area of the rat hippocampus following a kainic acid injection. Acta Neuropathol. (Berl.) 87, 187–195. Bhaskaran, M.D., Smith, B.N., 2010. Cannabinoid-mediated inhibition of recurrent excitatory circuitry in the dentate gyrus in a mouse model of temporal lobe epilepsy. PLoS ONE 5, e10683. Braakman, H.M.H., van Oostenbrugge, R.J., van Kranen-Mastenbroek, V.H.J.M., de Krom, M.C.T.F.M., 2009. Rimonabant induces partial seizures in a patient with a history of generalized epilepsy. Epilepsia 50, 2167–2173. Bragin, A., Wilson, C.L., Staba, R.J., Reddick, M., Fried, I., Engel Jr., J., 2002. Interictal high-frequency oscillations (80–500 Hz) in the human epileptic brain: entorhinal cortex. Ann. Neurol. 52, 407–415. Buckmaster, P.S., Dudek, F.E., 1997. Neuron loss, granule cell axon reorganization, and functional changes in the dentate gyrus of epileptic kainate-treated rats. J. Comp. Neurol. 385, 385–404. Buckmaster, P.S., Dudek, F.E., 1997. Network properties of the dentate gyrus in epileptic rats with hilar neuron loss and granule cell axon reorganization. J. Neurophysiol. 77, 2685–2696. Buzsáki, G., 2006. Rhythms of the Brain. Oxford University Press, New York, pp. 1– 464. Calderazzo, L., Cavalheiro, E.A., Macchi, G., Molinari, M., Bentivoglio, M., 1996. Branched connections to the septum and to the entorhinal cortex from the hippocampus, amygdala, and diencephalon in the rat. Brain Res. Bul. 40, 245– 251. Carriero, G., Arcieri, S., Cattalini, A., Corsi, L., Gnatkovsky, V., de Curtis, M., 2012. A guinea pig model of mesial temporal lobe epilepsy following nonconvulsive status epilepticus induced by unilateral intrahippocampal injection of kainic acid. Epilepsia 53 (11), 1917–1927. Carta, M., Fièvre, S., Gorlewicz, A., Mulle, C., 2014. Kainate receptors in the hippocampus. Eur. J. Neurosci. 39, 1835–1844. Cenquizca, L.A., Swanson, L.W., 2007. Spatial organization of direct hippocampal field CA1 axonal projections to the rest of the cerebral cortex. Brain Res. Rev. 56, 1–26. Chauvière, L., Rafrafi, N., Thinus-Blanc, C., Bartolomei, F., Esclapez, M., Bernard, C., 2009. Early deficits in spatial memory and theta rhythm in experimental temporal lobe epilepsy. J. Neurosci. 29, 5402–5410. Chen, K., Neu, A., Howard, A.L., Foldy, C., Echegoyen, J., Hilgenberg, L., Smith, M., Mackie, K., Soltesz, I., 2007. Prevention of plasticity of endocannabinoid signaling inhibits persistent limbic hyperexcitability caused by developmental seizures. J. Neurosci. 27, 46–58. Chen, S., Su, H., Yue, C., Remy, S., Royeck, M., Sochivko, D., Opitz, T., Beck, H., Yaari, Y., 2011. An increase in persistent sodium current contributes to intrinsic neuronal bursting after status epilepticus. J. Neurophysiol. 105, 117–129. Citraro, R., Russo, E., Ngomba, N.T., Nicoletti, F., Scicchitano, F., Whalley, B.J., Calignano, A., De Sarro, G., 2013. CB1 agonists, locally applied to the corticothalamic circuit of rats with genetic absence epilepsy, reduce epileptic manifestations. Epilepsy Res. 106, 74–82. Colom, L.V., 2006. Septal networks: relevance to theta rhythm, epilepsy and Alzheimer’s disease. J. Neurochem. 96, 609–624. Colom, L.V., Garcia, A., Sanabria, E.R., Castaneda, M.T., Perez-Cordova, M.G., 2006. Septo-hippocampal networks in chronically epileptic rats: potential antiepileptic effects of theta rhythm generation. J. Neurophysiol. 95, 3645– 3653. Coomber, B., O’Donoghue, F.M., Mason, R., 2008. Inhibition of endocannabinoid metabolism attenuates enhanced hippocampal neuronal activity induced by kainic acid. Synapse 62, 746–755. Cornish, S.M., Wheal, H.V., 1989. Long-term loss of paired pulse inhibition in the kainic acid-lesioned hippocampus of the rat. Neuroscience 28, 563–571. Covolan, L., Ribeiro, L.T., Longo, B.M., Mello, L.E., 2000. Cell damage and neurogenesis in the dentate granule cell layer of adult rats after pilocarpineor kainate-induced status epilepticus. Hippocampus. 10, 169–180. Cronin, J., Obenaus, A., Houser, C.R., Dudek, F.E., 1992. Electrophysiology of dentate granule cells after kainite induced synaptic reorganization of the mossy fibers. Brain Res. 573, 305–310. Davenport, C.J., Brown, W.J., Babb, T.L., 1990. GABAergic neurons are spared after intrahippocampal kainate in the rat. Epilepsy Res. 5, 28–42. Deshpande, L.S., Sombati, S., Blair, R.E., Carter, D.S., Martin, B.R., DeLorenzo, R.J., 2007. Cannabinoid CB1 receptor antagonists cause status epilepticus-like

activity in the hippocampal neuronl culture model of acquired epilepsy. Neurosci. Lett. 411, 11–16. Di Maio, R., Cannon, J.R., Timothy Greenamyre, J., 2015. Post-status epilepticus treatment with the cannabinoid agonist WIN 55,212–2 prevents chronic epileptic hippocampal damage in rats. Neurobiol. Dis. 73C, 356–365. Drexel, M., Preidt, A.P., Kirchmair, E., Sperk, G., 2011. Parvalbumin interneurons and calretinin fibers arising from the thalamic nucleus reuniens degenerate in the subiculum after kainic acid-induced seizures. Neuroscience 189, 316–329. Drexel, M., Preidt, A.P., Sperk, G., 2012. Sequel of spontaneous seizures after kainic acid-induced status epilepticus and associated neuropathological changes in the subiculum and entorhinal cortex. Neuropharmacology 63, 806–817. Du, F., Eid, T., Lothman, E.W., Köhler, C., Schwarcz, R., 1995. Preferential neuronal loss in layer III of the medial entorhinal cortex in rat models of temporal lobe epilepsy. J. Neurosci. 15, 6301–6313. Dudek, F.E., Shao, L.R., 2004. Mossy fiber sprouting and recurrent excitation: direct electrophysiologic evidence and potential implications. Epilepsy Curr. 4, 184– 187. Dudley, C.A., Lee, Y., Moss, R., 1990. Electrophysiological identification of pathway from the septal area to the medial amygdala: sensitivity to estrogen and luteinizing hormone releasing hormone. Synapse 6, 161–168. Dugladze, T., Vida, I., Tort, A.B., Gross, A., Otahal, J., Heinemann, U., Kopell, N.J., Gloveli, T., 2007. Impaired hippocampal rhythmogenesis in a mouse model of mesial temporal lobe epilepsy. Proc. Natl. Acad. Sci. U.S.A. 104, 17530–17535. Dümpelmann, M., Jacobs, J., Schulze-Bonhage, A., 2015. Temporal and spatial characteristics of high frequency oscillations as a new biomarker in epilepsy. Epilepsia 56, 197–206. Echegoyen, J., Armstrong, C., Morgan, R.J., Soltesz, I., 2009. Single application of a CB1 receptor antagonist rapidly following head injury prevents long-term hyperexcitability in a rat model. Epilepsy Res. 85, 123–127. Esclapez, M., Hirsch, J.C., Ben-Ari, Y., Bernard, C., 1999. Newly formed excitatory pathways provide a substrate for hyperexcitability in experimental temporal lobe epilepsy. J. Comp. Neurol. 408, 449–460. Franck, J.E., 1984. Dynamic alterations in hippocampal morphology following intraventricular kainic acid. Acta Neuropathol. 62, 242–253. Fritsch, B., Qashu, F., Figueiredo, T.H., Aroniadou-Anderjaska, V., Rogawski, M.A., Braga, M.F., 2009. Pathological alterations in GABAergic interneurons and reduced tonic inhibition in the basolateral amygdala during epileptogenesis. Neuroscience 163, 415–429. Garrido-Sanabria, E.R., Castañeda, M.T., Banuelos, C., Perez-Cordova, M.G., Hernandez, S., Colom, L.V., 2006. Septal GABAergic neurons are selectively vulnerable to pilocarpine-induced status epilepticus and chronic spontaneous seizures. Neuroscience 142, 871–883. Gordon, R.Ya., Shubina, L.V., Kapralova, M.V., Pershina, E.V., Khutzian, S.S., Arhipov, V.I., 2015. Peculiarities of neurodegeneration of hippocampus fields after the action of kainic acid in rats. Cell Tissue Biol. 9, 141–148. Hammonds, M.D., Shim, S.S., Feng, P., Calabrese, J.R., 2007. Effects of subchronic lithium treatment on levels of BDNF, Bcl-2 and phospho-CREB in the rat hippocampus. Basic Clin. Pharmacol. Toxicol. 100, 356–359. Hansen, H.H., Schmid, P.C., Bittigau, P., Lastres-Becker, I., Berrendero, F., Manzanares, J., Ikonomidou, C., Schmid, H.H., Fernandez-Ruiz, J.J., Hansen, H. S., 2001. Anandamide, but not 2-arachidonoylglycerol, accumulates during in vivo neurodegeneration. J. Neurochem. 78, 1415–1427. Kano, M., Ohno-Shosaku, T., Hashimotodani, Y., Uchigashima, M., Watanabe, M., 2009. Endocannabinoid-mediated control of synaptic transmission. Physiol. Rev. 89, 309–380. Karanian, D.A., Brown, Q.B., Makriyannis, A., Kosten, T.A., Bahr, B.A., 2005. Dual modulation of endocannabinoid transport and fatty-acid amide hydrolase protects against excitotoxicity. J. Neurosci. 25, 7813–7820. Karanian, D.A., Karim, S.L., Wood, J.T., Williams, J.S., Lin, S., Makriyannis, A., Bahr, B. A., 2007. Endocannabinoid enhancement protects against kainic acid-induced seizures and associated brain damage. J. Pharmacol. Exp. Ther. 322, 1059–1066. Karlócai, M.R., Tóth, K., Watanabe, M., Ledent, C., Juhász, G., Freund, T.F., Maglóczky, Z., 2011. Redistribution of CB1 cannabinoid receptors in the acute and chronic phases of pilocarpine-induced epilepsy. PLoS ONE 6, e27196. Khaspekov, L.G., BrenzVerca, M.S., Frumkina, L.E., Hermann, H., Marsicano, G., Lutz, B., 2004. Involvement of brain-derived neurotrophic factor in cannabinoid receptor-dependent protection against excitotoxicity. Eur. J. Neurosci. 19, 1691–1698. Kitchigina, V., Popova, I., Sinelnikova, V., Malkov, A., Astasheva, E., Shubina, L., Aliev, R., 2013. Disturbances of septohippocampal theta oscillations in the epileptic brain: Reasons and consequences. Exp. Neurol. 247, 314–327. Kitchigina, V.F., Butuzova, M.V., 2009. Theta activity of septal neurons during different epileptic phases: the same frequency but different significance? Exp. Neurol. 216, 449–458. Kozan, R., Ayyildiz, M., Agar, E., 2009. The effects of intracerebroventricular AM-251, a CB1-receptor antagonist, and ACEA, a CB1-receptor agonist, on penicillininduced epileptiform activity in rats. Epilepsia 50, 1760–1767. Krook-Magnuson, E., Armstrong, C., Bui, A., Lew, S., Oijala, M., Soltesz, I., 2015. In vivo evaluation of the dentate gate theory in epilepsy. J. Physiol. 593, 2379–2388. Kumar, S.S., Buckmaster, P.S., 2006. Hyperexcitability, interneurons, and loss of GABAergic synapses in entorhinal cortex in a model of temporal lobe epilepsy. J. Neurosci. 26, 4613–4623. Leranth, C., Carpi, D., Buzsaki, G., Kiss, J., 1999. The entorhino-septosupramammillary nucleus connection in the rat: morphological basis of a feedback mechanism regulating hippocampal theta rhythm. Neuroscience 88, 701–718.

L. Shubina et al. / Brain Research 1661 (2017) 1–14 Levesque, M., Avoli, M., 2013. The kainic acid model of temporal lobe epilepsy. Neurosci. Biobehav. Rev. 37, 2887–2899. Lourenço, J., Matias, I., Marsicano, G., Mulle, C., 2011. Pharmacological activation of kainate receptors drives endocannabinoid mobilization. J. Neurosci. 31, 3243– 3248. Ma, L., Wang, L., Yang, F., Meng, X.-D., Wu, C., Ma, H., Jiang, W., 2014. Diseasemodifying effects of RHC80267 and JZL184 in a pilocarpine mouse model of temporal lobe epilepsy. CNS Neurosci. Ther. 20, 905–915. Maglóczky, Z., Freund, T.F., 2005. Impaired and repaired inhibitory circuits in the epileptic human hippocampus. Trends Neurosci. 28, 334–340. Maglóczky, Z., Tóth, K., Karlócai, R., Nagy, S., Eross, L., Czirják, S., Vajda, J., Rásonyi, G., Kelemen, A., Juhos, V., Halász, P., Mackie, K., Freund, T.F., 2010. Dynamic changes of CB1-receptor expression in hippocampi of epileptic mice and humans. Epilepsia 51 (S3), 115–120. Malkov, A.E., Popova, I.Yu., 2011. Functional changes in the septal GABAergic system of animals with a model of temporal lobe epilepsy. Gen. Physiol. Biophys. 30, 310–320. Manna, S.S., Umathe, S., 2012. Involvement of transient receptor potential vanilloid type 1 channels in the pro-convulsant effect of anandamide in pentylenetetrazole-induced seizures. Epilepsy Res. 100, 113–124. Marcelin, B., Chauvière, L., Becker, A., Migliore, M., Esclapez, M., Bernard, C., 2009. H channel-dependent deficit of theta oscillation resonance and phase shift in temporal lobe epilepsy. Neurobiol. Dis. 33, 36–47. Marsicano, G., Goodenough, S., Monory, K., Hermann, H., Eder, M., Cannich, A., Azad, S.C., Cascio, M.G., Gutierrez, S.O., van der Stelt, M., Lopez-Rodriguez, M.L., Casanova, E., Schutz, G., Zieglgansberger, W., Di Marzo, V., Behl, C., Lutz, B., 2003. CB1 cannabinoid receptors and on-demand defense against excitotoxicity. Science 302, 84–88. Mason, R., Cheer, J.F., 2009. Cannabinoid receptor activation reverses kainateinduced synchronized population burst firing in rat hippocampus. Front. Int. Neurosci. 3, 1–6. Mayer, S.A., Claassen, J., Lokin, J., Mendelsohn, F., Dennis, L.J., Fitzsimmons, B.F., 2002. Refractory status epilepticus: frequency, risk factors, and impact on outcome. Arch. Neurol. 59, 205–210. Mazarati, A.M., Baldwin, R.A., Sankar, R., Wasterlain, C.G., 1998. Time-dependent decrease in the effectiveness of antiepileptic drugs during the course of selfsustaining status epilepticus. Brain Res. 814, 179–185. Meibach, R.C., Siegel, A., 1977. Efferent connections of the septal area in the rat: an analysis utilizing retrograde and anterograde transport methods. Brain Res. 119, 1–20. Meier, C.L., Dudek, F.E., 1996. Spontaneous and stimulation-induced synchronized burst afterdischarges in the isolated CA1 of kainate-treated rats. J. Neurophysiol. 76, 2231–2239. Meier, C.L., Obenaus, A., Dudek, F.E., 1992. Persistent hyperexcitability in isolated hippocampal CA1 of kainate-lesioned rats. J. Neurophysiol. 68, 2120–2127. Monory, K., Massa, F., Egertova, M., Eder, M., Blaudzun, H., Westenbroek, R., Kelsch, W., Jacob, W., Marsch, R., Ekker, M., Long, J., Rubenstein, J.L., Goebbels, S., Nave, K.A., During, M., 2006. The endocannabinoid system controls key epileptogenic circuits in the hippocampus. Neuron 51, 455–466. Morin, F., Beaulieu, C., Lacaille, J.C., 1998. Selective loss of GABA neurons in area CA1 of the rat hippocampus after intraventricular kainite. Epilepsy Res. 32, 363–369. Naderi, N., Ahmad-Molaei, L., AzizAhari, F., Motamedi, F., 2011. Modulation of anticonvulsant effects of cannabinoid compounds by GABA-A receptor agonist in acute pentylenetetrazole model of seizure in rat. Neurochem. Res. 36, 1520– 1525. Naderi, N., AzizAhari, F., Shafaghi, B., Najarkolaei, A.H., Motamedi, F., 2008. Evaluation of interactions between cannabinoid compounds and diazepam in electroshock-induced seizure model in mice. J. Neural. Transm. 115, 1501– 1511. Nadler, J.V., 1981. Kainic acid as a tool for the study of temporal lobe epilepsy. Life Sci. 29, 2031–2042. Naidoo, V., Karanian, D.A., Vadivel, S.K., Locklear, J.R., Wood, J.T., Nasr, M., Quizon, P. M., Graves, E.E., Shukla, V., Makriyannis, A., Bahr, B.A., 2012. Equipotent inhibition of fatty acid amide hydrolase and monoacylglycerol lipase – dual targets of the endocannabinoid system to protect against seizure pathology. Neurotherapeutics 9, 801–813. Naidoo, V., Nikas, S.P., Karanian, D.A., Hwang, J., Zhao, J., Wood, J.T., Alapafuja, S.O., Vadivel, S.K., Butler, D., Makriyannis, A., Bahr, B.A., 2011. A new generation fatty acid amide hydrolase inhibitor protects against kainate-induced excitotoxicity. J. Mol. Neurosci. 43, 493–502. O’Donovan, K.J., Tourtellotte, W.G., Millbrandt, J., Baraban, J.M., 1999. The EGR family of transcription-regulatory factors: progress at the interface of molecular and systems neuroscience. Trends Neurosci. 22, 167–173. Palazuelos, J., Aguado, T., Egia, A., Mechoulam, R., Guzman, M., Galve-Roperh, I., 2006. Non-psychoactive CB2 cannabinoid agonists stimulate neural progenitor proliferation. FASEB J. 20, 2405–2407. Panikashvili, D., Simeonidou, C., Ben-Shabat, S., Hanus, L., Breuer, A., Mechoulam, R., Shohami, E., 2001. An endogenous cannabinoid (2-AG) is neuroprotective after brain injury. Nature 413, 527–531. Parent, J.M., Yu, T.W., Leibowitz, R.T., Geschwind, D.H., Sloviter, R.S., Lowenstein, D. H., 1997. Dentate granule cell neurogenesis is increased by seizures and contributes to aberrant network reorganization in the adult rat hippocampus. J. Neurosci. 17, 3727–3738. Perez, Y., Morin, F., Beaulieu, C., Lacaille, J.C., 1996. Axonal sprouting of CA1 pyramidal cells in hyperexcitable hippocampal slices of kainate-treated rats. Eur. J. Neurosci. 8, 736–748.

13

Pitkänen, A., Tuunanen, J., Kälviäinen, R., Partanen, K., Salmenperä, T., 1998. Amygdala damage in experimental and human temporal lobe epilepsy. Epilepsy Res. 32, 233–253. Pitkänen, A., Savander, V., LeDoux, J.L., 1997. Organization of intra-amygdaloid circuitries: an emerging framework for understanding functions of the amygdale. Trends Neurosci. 20, 517–523. Polascheck, N., Bankstahl, M., Loscher, W., 2010. The COX-2 inhibitor parecoxib is neuroprotective but not antiepileptogenic in the pilocarpine model of temporal lobe epilepsy. Exp. Neurol. 224, 219–233. Popova, I.Y., Sinelnikova, V.V., Kitchigina, V.F., 2008. Disturbance of the correlation between hippocampal and septal EEGs during epileptogenesis. Neurosci. Lett. 442, 228–233. Racine, R.J., 1972. Modification of seizure activity by electrical stimulation. II. Motor seizure. Electroencephalogr. Clin. Neurophysiol. 32, 281–294. Rapisarda, C., Bacchelli, B., 1977. The brain of the guinea pig in stereotaxic coordinates. Arch. Sci. Biol. 61, 1–37. Risold, P.Y., Swanson, L.W., 1997. Connections of the rat lateral septal complex. Brain Res. 24, 115–195. Rizzo, V., Ferraro, G., Carletti, F., Lonobile, G., Cannizzaro, C., Sardo, P., 2009. Evidences of cannabinoids-induced modulation of paroxysmal events in an experimental model of partial epilepsy in the rat. Neurosci. Let. 462, 135–139. Sah, P., Faber, E.S., Lopez De Armentia, M., Power, J., 2003. The amygdaloid complex: anatomy and physiology. Physiol. Rev. 83, 803–834. Sakatani, S., Seto-Ohshima, A., Itohara, S., Hirase, H., 2007. Impact of S100B on local field potential patterns in anesthetized and kainic acid-induced seizure conditions in vivo. Eur. J. Neurosci. 25, 1144–1154. Salami, P., Lévesque, M., Benini, R., Behr, C., Gotman, J., Avoli, M., 2014. Dynamics of interictal spikes and high-frequency oscillations during epileptogenesis in temporal lobe epilepsy. Neurobiol. Dis. 67, 97–106. Scholl, E.A., Dudek, F.E., Ekstrand, J.J., 2013. Neuronal degeneration is observed in multiple regions outside the hippocampus after lithium pilocarpine-induced status epilepticus in the immature rat. Neuroscience 252, 45–59. Shafaroodi, H., Samini, M., Moezi, L., Homayoun, H., Sadeghipour, H., Tavakoli, S., Hajrasouliha, A.R., Dehpour, A.R., 2004. The interaction of cannabinoids and opioids on pentylenetetrazole- induced seizure threshold in mice. Neuropharmacology 47, 390–400. Shao, L.R., Dudek, F.E., 2004. Increased excitatory synaptic activity and local connectivity of hippocampal CA1 pyramidal cells in rats with kainate-induced epilepsy. J. Neurophysiol. 92, 1366–1373. Shao, L.R., Dudek, F.E., 2005. Changes in mIPSCs and sIPSCs after kainate treatment: evidence for loss of inhibitory input to dentate granule cells and possible compensatory responses. J. Neurophysiol. 94, 952–960. Shubina, L., Aliev, R., Kitchigina, V., 2015. Attenuation of kainic acid-induced status epilepticus by inhibition of endocannabinoid transport and degradation in guinea pigs. Epilepsy Res. 111, 33–44. Shubina, L.V., Kichigina, V.F., 2012. Protective effects of the CB1 receptor agonist WIN 55.212-2 during development of seizure activity in the brain in models of temporal epilepsy in vivo. Neurosci. Behav. Physiol. 42, 582–587. Sinel’nikova, V.V., Kichigina, V.F., 2011. [Changes in the electrical activity of the medial septal region, piriform cortex and amygdala during epileptogenesis in the model of temporal lobe epilepsy]. Zh. Vyssh. Nerv. Deiat. Im. I.P. Pavlova 61, 219–226 (in Russian). Sloviter, R.S., Zappone, C.A., Harvey, B.D., Frotscher, M., 2006. Kainic acid-induced recurrent mossy fiber innervation of dentate gyrus inhibitory interneurons: possible anatomical substrate of granule cell hyper- inhibition in chronically epileptic rats. J. Comp. Neurol. 494, 944–960. Smith, B.N., Dudek, F.E., 2001. Short- and long-term changes in CA1 network excitability after kainate treatment in rats. J. Neurophysiol. 85, 1–9. Smith, B.N., Dudek, F.E., 2002. Network interactions mediated by new excitatory connections between CA1 pyramidal cells in rats with kainate-induced epilepsy. J. Neurophysiol. 87, 1655–1658. Staba, R.J., Stead, M., Worrell, G.A., 2014. Electrophysiological biomarkers of epilepsy. Neurotherapeutics 11, 334–346. Stafstrom, C.E., 2007. Persistent sodium current and its role in epilepsy. Epilepsy Curr. 7, 15–22. Suleymanova, E.M., Shangaraeva, V.A., van Rijn, C.M., Vinogradova, L.V., 2016. The cannabinoid receptor agonist WIN55.212 reduces consequences of status epilepticus in rats. Neuroscience 334, 191–200. Szilágyi, T., Száva, I., Metz, E.J., Mihály, I., Orbán-Kis, K., 2014. Untangling the pathomechanisms of temporal lobe epilepsy – the promise of epileptic biomarkers and novel therapeutic approaches. Brain Res. Bull. 109, 1–12. Tauck, D.L., Nadler, J.V., 1985. Evidence of functional mossy fiber sprouting in hippocampal formation of kainic acid-treated rats. J. Neurosci. 5, 1016–1022. Tuunanen, J., Halonen, T., Pitkänen, A., 1996. Seizures cause selective regional damage and loss of GABAergic neurons in the rat amygdaloid complex. Eur. J. Neurosci. 8, 2711–2725. van der Stelt, M., Mazzola, C., Esposito, G., Matias, I., Petrosino, S., De Filippis, D., Micale, V., Steardo, L., Drago, F., Iuvone, T., Di Marzo, V., 2006. Endocannabinoids and beta-amyloid-induced neurotoxicity in vivo: effect of pharmacological elevation of endocannabinoid levels. Cell. Mol. Life Sci. 63, 1410–1424. van Groen, T., Miettinen, P., Kadish, I., 2003. The entorhinal cortex of the mouse: organization of the projection to the hippocampal formation. Hippocampus 13, 133–149. van Rijn, C.M., Perescis, M.F., Vinogradova, L., van Luijtelaar, G., 2011. Endocannabinoid system protects against cryptogenic seizures. Pharmacol. Rep. 63, 165–168.

14

L. Shubina et al. / Brain Research 1661 (2017) 1–14

Vilela, L.R., Medeiros, D.C., Rezende, G.H., de Oliveira, A.C., Moraes, M.F., Moreira, F. A., 2013. Effects of cannabinoids and endocannabinoid hydrolysis inhibition on pentylenetetrazole-induced seizure and electroencephalographic activity in rats. Epilepsy Res. 104, 195–202. Vinogradova, L.V., van Rijn, C.M., 2015. Long-term disease-modifying effect of the endocannabinoid agonist WIN55,212–2 in a rat model of audiogenic epilepsy. Pharm. Rep. 67, 501–503. Vinogradova, L.V., Shatskova, A.B., van Rijn, C.M., 2011. Pro-epileptic effects of the cannabinoid receptor antagonist SR141716 in a model of audiogenic epilepsy. Epilepsy Res. 96, 250–256. Vinogradova, O.S., 1995. Expression, control and probable functional significance of the neuronal theta-rhythm. Progr. Neurobiol. 45, 523–583. Wallace, M.J., Blair, R.E., Falenski, K.W., Martin, B.R., DeLorenzo, R.J., 2003. The endogenous cannabinoid system regulates seizure frequency and duration in a model of temporal lobe epilepsy. J. Pharmacol. Exp. Ther. 307, 129–137. Wallace, M.J., Martin, B.R., DeLorenzo, R.J., 2002. Evidence for a physiologicalrole of endocannabinoids in the modulation of seizure threshold and severity. Eur. J. Pharmacol. 452, 295–301. Wallace, M.J., Wiley, J.L., Martin, B.R., DeLorenzo, R.J., 2001. Assessment of the role of CB1 receptors in cannabinoid anticonvulsant effects. Eur. J. Pharmacol. 428, 51–57.

Wang, X.J., Buzsáki, G., 1996. Gamma oscillation by synaptic inhibition in a hippocampal interneuronal network model. J. Neurosci. 16, 6402–6413. Wendt, H., Soerensen, J., Wotjak, C.T., Potschka, H., 2011. Targeting the endocannabinoid system in the amygdala kindling model of temporal lobe epilepsy in mice. Epilepsia 52, e62–e65. Wenzel, H.J., Woolley, C.S., Robbins, C.A., Schwartzkroin, P.A., 2000. Kainic acidinduced mossy fiber sprouting and synapse formation in the dentate gyrus of the rat. Hippocampus 10, 244–260. Wettschureck, N., van der Stelt, M., Tsubokawa, H., Krestel, H., Moers, A., Petrosino, S., Schutz, G., Di Marzo, V., Offermanns, S., 2006. Forebrain-specific inactivation of Gq/G11 family G proteinsresults in age-dependentepilepsy and impairedendocannabinoid formation. Mol. Cell. Biol. 26, 5888–5894. Xu, H., Steven Richardson, J., Li, X.M., 2003. Dose-related effects of chronic antidepressants on neuroprotective proteins BDNF, Bcl-2 and Cu/Zn-SOD in rat hippocampus. Neuropsychopharmacology 28, 53–62. Ylinen, A., Soltész, I., Bragin, A., Penttonen, M., Sik, A., Buzsáki, G., 1995. Intracellular correlates of hippocampal theta rhythm in identified pyramidal cells, granule cells, and basket cells. Hippocampus 5, 78–90. Zhang, X., Cui, S.S., Wallace, A.E., Hannesson, D.K., Schmued, L.C., Saucier, D.M., Honer, W.G., Corcoran, M.E., 2002. Relations between brain pathology and temporal lobe epilepsy. J. Neurosci. 22, 6052–6061.