Corticosterone modulates fear responses and the expression of glucocorticoid receptors in the brain of high-anxiety rats

Neuroscience Letters 533 (2013) 17–22

Contents lists available at SciVerse ScienceDirect

Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet

Corticosterone modulates fear responses and the expression of glucocorticoid receptors in the brain of high-anxiety rats b ´ A. Wisłowska-Stanek a,∗ , M. Lehner b , A. Skórzewska b , P. Maciejak a,b , J. Szyndler a , D. Turzynska , b a,b ´ A. Sobolewska , A. Płaznik a b

Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, 26/28 Krakowskie Przedmie´scie Street, 00-927 Warsaw, Poland Department of Neurochemistry, Institute of Psychiatry and Neurology, 9 Sobieskiego Street, 02-957 Warsaw, Poland

h i g h l i g h t s  High anxiety rats (HR) have a lower expression of GRs to aversive context.  Corticosterone attenuates conditioned fear in HR.  Corticosterone potentiates the expression of GRs in the limbic structures of HR.

a r t i c l e

i n f o

Article history: Received 13 July 2012 Received in revised form 31 October 2012 Accepted 3 November 2012 Keywords: Conditioned freezing Corticosterone Glucocorticoid receptors Prefrontal cortex Dentate gyrus High- and low-anxiety rats

a b s t r a c t The aim of our experiments was to assess the effect of acutely administered corticosterone on the expression of glucocorticoid receptors (GRs) in the brain of rats with high (HR) and low (LR) levels of anxiety. The rats were divided into groups according to their conditioned fear-induced freezing responses and then were subjected to a second conditioned fear session one week after the initial fear conditioning. Immunocytochemical analysis revealed that the second exposure to contextual aversive stimuli resulted in higher levels of GRs expression in cingulate cortex area 1 (Cg1), the secondary motor cortex (M2) of the prefrontal cortex and the dentate gyrus of the hippocampus (DG) in LR rats compared with HR rats. The pretreatment of HR rats with corticosterone (20 mg/kg, sc) increased the expression levels of GRs in Cg1, the M2 area and the DG to the levels observed in the LR vehicle group. The increase in the GRs levels was accompanied by a significant decrease in the conditioned fear response in the HR group. The control animals that were not exposed to aversive stimuli had similar levels of receptor-related immunoreactivity in all brain regions, and corticosterone did not change these expression levels. Our results suggest that HR animals may have deficits in the expression of stress-induced GRs in the prefrontal cortex and the DG. In addition, pretreatment with corticosterone increases the expression of GRs and normalizes the fear response in HR rats. © 2012 Elsevier Ireland Ltd. All rights reserved.

1. Introduction Glucocorticoids are potent stress hormones that are implicated in the short- and long-term adaptation to stressors and facilitate active coping in threatening situations [8]. Glucocorticoid receptors (GRs) are richly expressed in brain regions that mediate changes in the HPA (hypothalamic-pituitary-adrenal) axis and play roles in emotional processing, including the prefrontal cortex, the hippocampus and the amygdala [8]. Glucocorticoids readily enter the brain and affect aversive learning and memory [5]. Some preclinical and clinical data suggest that glucocorticoids can reduce the retrieval of aversive memories and may be

∗ Corresponding author. Tel.: +48 22 8262116; fax: +48 22 8262116. E-mail address: [email protected] (A. Wisłowska-Stanek). 0304-3940/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neulet.2012.11.012

useful in patients with phobias and post-traumatic stress disorder (PTSD) [1,5,6]. Glucocorticoids also facilitate extinction and enhance extinction-based psychotherapy in patients with phobias [5]. Functional neuroimaging studies have revealed that patients with PTSD, show exaggerated amygdala responses and deficient prefrontal cortex function, especially in the anterior cingulate cortex and the ventromedial prefrontal cortex [19,21]. Preclinical data indicate that the information from widespread areas of the cortex is integrated by the dorsal prefrontal cortex (the medial frontal agranular cortex and the anterior cingulated cortex) during goal directed action [10]. Both preclinical and clinical evidence suggest that the prefrontal cortex may influence contextual fear conditioning and extinction by contributing to the integration of information about the encoded environment via the amygdala and contextual information from the hippocampus [7,11].

18

A. Wisłowska-Stanek et al. / Neuroscience Letters 533 (2013) 17–22

In our laboratory, we elaborated the model of high- (HR) and low-anxiety (LR) rats, which were selected based on the duration of their conditioned freezing response in a contextual fear test. Previously, we found that LR rats had a higher GRs immunoreactivity in the prefrontal cortex, and the HR group showed enhanced receptor-related immunoreactivity in the basolateral amygdala after a fear conditioning test [15,16]. We also observed that the freezing response of HR rats could be attenuated by d-cycloserine and midazolam or by repeated exposition to the aversive context (extinction training) [17]. In the present study, we decided to analyze the central effects of glucocorticoids in our model of individual propensity for anxiety disorders. More specifically, we investigated the effects of acutely administered corticosterone on the expression of GRs in the brain of HR and LR rats subjected to an aversive context one week after a contextual fear test. It should be noted that the brains analyzed in this experiment were also used in a study involving corticosteroneinduced changes in the expression of the alpha-2 subunit of GABA-A receptors [26]. We chose to present the results of these studies separately because of the volume of experimental data and the divergent roles of the aforementioned receptor proteins in the regulation of emotions. 2. Experimental procedures 2.1. Animals The experiments were performed on a cohort of 71 male Wistar rats. The rats (180–200 g body weight) were purchased from a licensed breeder and were housed under standard laboratory conditions with a 12 h light/dark cycle (lights on at 7 a.m.) at a constant temperature (21 ± 2 ◦ C). The experiments were performed in accordance with the European Communities Council Directive of 24 November 1986 (86/609 EEC). The Local Committee for Animal Care and Use at the Warsaw Medical University, Poland, approved all experimental procedures using animals. 2.2. Experimental protocol The experiment was performed in the two parts: (1) an experiment that assessed the influence of corticosterone (20 mg/kg, sc) on GRs expression and rat behavior after the conditioned fear test session (T2) on the 8th day after the contextual fear conditioning test (T1), and (2) a control experiment in which we assessed the influence of corticosterone alone (20 mg/kg, sc) on the expression of GRs in selected brain structures. 2.2.1. Contextual fear test After four days of acclimatization, the animals (n = 40) were subjected to a conditioned fear test as previously described by Wisłowska-Stanek et al. [25]. The fear conditioning was performed in an experimental cage (36 cm × 21 cm × 20 cm, w/l/h) under constant white noise conditions (65 dB). The experiment lasted 3 consecutive days. On the 1st day, the animals were individually placed in a training box for 2 min to adapt to the experimental conditions. The following day, after 5 min of habituation in the training box, the animals were subjected to a fear conditioning procedure that consisted of each animal receiving three footshocks (stimulus: 0.7 mA, 1 s, repeated every 59 s). Conditioned fear was tested on the 3rd day (test day, T1) by re-exposing rats to the testing box and recording the freezing response over 10 min (freezing was measured by photo beams with a 10 Hz detection rate controlled by the fear conditioning software). The rats (mean freezing duration: 246 s; SEM = 21.9 s) were divided into two experimental groups according to the duration of context-induced freezing responses for: LR group that means low anxiety rats, with a

Table 1 The rat freezing behavior. T1

T2

LR-T1 (n = 18)

143 ± 17.5

LR-T2-v (n = 7) LR-T2-cort (n = 9)

90.6 ± 31.7 112.1 ± 49.7

HR-T1 (n = 16)

346 ± 18.6**

HR-T2-v (n = 8) HR-T2-cort (n = 8)

249.2 ± 30.5&& 147.1 ± 27.3#

The data are shown as means ± SEM. T1, the first conditioning fear session; T2, second fear session; LR-T1, low-anxiety rats; HR-T1, high-anxiety rats; LR-T2-v, low-anxiety rats pretreated with vehicle; HR-T2-v, high-anxiety rats, pretreated with vehicle; LR-T2-cort, low-anxiety rats pretreated with corticosterone; HR-T2cort, high-anxiety rats, pretreated with corticosterone. For more detail, see Section 2. ** Differs from LR-T1, P < 0.01. && Differs from LR-T2-v, P < 0.01. # Differs from HR-T2-v, P < 0.05.

total duration of freezing responses one SEM or more below the mean < 224.1 s (246–21.9); and HR group consisting of high anxiety rats, HR > 267.9 s (246 + 21.9). Thus, the LR and HR animals did not overlap with respect to the duration of their conditioned fear responses (these animals are designated LR-T1 and HR-T1) (Table 1). Additionally, the control group (n = 6) consisted of animals that were not conditioned to the aversive context but were placed in the conditioning boxes only (mean freezing duration: 92.7 s; SEM = 24.45). After conditioning, animals remained undisturbed in their home cages, and then 8 days later, they were subjected to the aversive context in the second fear session (T2). On this day, the LR-T1 and HR-T1 groups were subsequently divided into following subgroups: LR-T2-v, low-anxiety rats given vehicle; LR-T2-cort, low-anxiety rats given corticosterone; HR-T2-v, high-anxiety rats given vehicle; and HR-T2-cort, high-anxiety rats given corticosterone. The drug was given 30 min before the T2 session, and the appropriate groups of animals were decapitated 2 h after drug or vehicle administration and 90 min after the T2 session. 2.2.2. Control experiment without the T2 session A control study was performed on another group of animals (n = 25). The paradigm of this experiment was the same as that previously described except that a second fear test session (T2) was not performed. These animals were injected with vehicle or corticosterone 8 days after T1 and decapitated 2 h later. Pre-selected rats, LR < 230.7 s (256.4–25.7) and HR > 282.1 s (256.4 + 25.7) were divided into the following four groups: LR-v, low-anxiety rats given vehicle; LR-cort, low-anxiety rats given corticosterone; HR-v, highanxiety rats given vehicle; and HR-cort, high-anxiety rats given corticosterone. 2.3. Drugs Corticosterone (Sigma–Aldrich, Poland) was suspended in sesame oil at an adjusted volume of 1 ml/kg of body weight and was administered subcutaneously to the nape of the neck. The dose of 20 mg/kg was selected based on our previous studies, and literature data [2,20,22–24]. The control rats were administered the same volume of sesame oil alone (Sigma–Aldrich, Poland). 2.4. GRs immunostaining Imunocytochemical staining for the GRs was performed on slide-mounted frozen brain coronal sections (15 ␮m), fixed in methanol for 5 min. Three slices from each section identified using the rat brain atlas [18] were taken. After blocking activity

A. Wisłowska-Stanek et al. / Neuroscience Letters 533 (2013) 17–22

19

Fig. 1. (A) Diagrams adapted from Paxinos and Watson [18] showing the regions of the brain analyzed for the expression of GRs. BLA, basolateral amygdala; Cg1 and Cg2, cingulate area 1 and 2; CPu, caudate putamen; DG, dentate gyrus of the hippocampus; M2 area, secondary motor cortex. Shaded areas indicate the analyzed brain regions. (B) Microphotographs showing the representative expression of GRs in the DG in HR animals exposed to aversive context. HR-T2-v, high anxiety rats pretreated with vehicle; HR-T2-cort, high anxiety rats pretreated with corticosterone. Slices were photographed with magnification 10×. Bar indicates 150 ␮m.

of endogenous peroxidase and non-specific binding, the primary antibody for GRs (1:1000 Thermo Scientific; MA1-510) was incubated with the samples at 4–8 ◦ C for 72 h and was then detected with biotinylated anti-rabbit IgGs (1:1000, Vector Laboratories, CA) and avidin–biotin-peroxidase complex (Vector Laboratories, CA). The peroxidase reaction was developed with DAB (0.2 mg/ml) and hydrogen peroxide (0.003%) in Tris buffer. Next, the sections were dehydrated by serial alcohol rinsing, cleared in xylene, and coverslipped in the histofluid mounting medium. The number of clearly identified glucocorticosteroid receptorpositive cells was manually counted using image analysis system (Olympus DP-soft version 3.2 software) in the following subregions: cingulated cortex areas 1 and 2, the secondary motor cortex (Cg1, Cg2, M2, AP: 1.20), the basolateral amygdala and the dentate gyrus of the hippocampus (BLA, DG, AP: −3.14) (Fig. 1A and B). The examined areas were sampled using a 0.2 mm × 0.2 mm frame placed within the appropriate region, images were captured, and counts were expressed as the number of positive nuclei

per mm2 . Control experiments performed without primary or secondary antibodies (to detect non-specific binding of antibodies and endogenous peroxidase activity) yielded negative results. Western blot analysis performed with the same antibody (1:200) on the homogenates from rats amygdala confirmed specific band at about 90 kDa [9].

2.5. Statistical data The differences in the duration of the freezing response during the first and second conditioning fear tests (T1 and T2) in the LR and HR groups were analyzed by one-way ANOVA with repetitions, followed by Tukey’s post hoc test. The behavioral data from the second test session and the immunocytochemical data were analyzed by three-way ANOVA followed by the Tukey’s post hoc test. For correlation analyses, Pearson coefficients were calculated. A probability value of P < 0.05 was considered significant in this study.

20

A. Wisłowska-Stanek et al. / Neuroscience Letters 533 (2013) 17–22

Cg1 (cell number/1 mm 2)

350

1

300

[F(1,42)=17.86 (P<0.01)] [F(1,42)=8.69 (P<0.01)] [F(1,42)=2.60 (P=0.11)] 4 [F(1,42)=6.22 (P<0.05)] 5 [F(1,42)=7.89 (P<0.01)] 6 [F(1,42)=0.04 (P=0.84)] 7 [F(1,42)=4.04 (P=0.05)] 2

P<0.01

250

P<0.05

200

3

P<0.05

150 100 50 0 HR-v

HR-cort

HR-T2-v

HR-T2-cort

LR-v

LR-cort

LR-T2-v

LR-T2-cort

Cg2 (cell number/1 mm2)

350

1

[F(1,42)=0.23 (P=0.64)] [F(1,42)=0.12 (P=0.74)] [F(1,42)=1.73 (P=0.20)] 4 [F(1,42)=4.60 (P<0.05)] 5 [F(1,42)=0.81 (P=0.37)] 6 [F(1,42)=2.97 (P=0.09)] 7 [F(1,42)=0.16 (P=0.69)]

300

2 3

250 200 150 100 50 0 HR-v

HR-cort

HR-T2-v

HR-T2-cort

LR-v

LR-cort

LR-T2-v

LR-T2-cort

P<0.05 P<0.01 P<0.01

M2 area (cell number/1 mm2 )

350

P<0.01 P<0.01

300

P<0.01 P<0.01

1

[F(1,49)=4.20 (P<0.05)] [F(1,49)=2.13 (P=0.15)] [F(1,49)=111.2 P<0.01)] 4 [F(1,49)=18.15 (P<0.01)] 5 [F(1,49)=2.04 (P=0.16)] 6 [F(1,49)=0.02 (P=0.9)] 7 [F(1,49)=12.87 (P<0.01) 2 3

250 200 150 100 50 0 HR-v

HR-cort

HR-T2-v

HR-T2-cort

LR-v

LR-cort

LR-T2-v

LR-T2-cort

BLA (cell number/1 mm2)

350

1

[F(1,49)=2.18 (P=0.15)] [F(1,49)=0.07 (P=0.8)] [F(1,49)=0.09 P=0.76)] 4 [F(1,49)=3.21 (P=0.08)] 5 [F(1,49)=4.95 (P<0.05)] 6 [F(1,49)=0.03 (P=0.86)] 7 [F(1,49)=0.35 (P=0.55)]

300

2 3

250 200 150 100 50 0 HR-v

HR-cort

HR-T2-v

HR-T2-cort

LR-v

LR-cort

LR-T2-v

LR-T2-cort

DG (cell number/1 mm2)

350

1

300

P<0.01

250

P<0.01 P<0.01

200

[F(1,49)=7.45 (P<0.01)] [F(1,49)=6.17 (P<0.05)] [F(1,49)=47.11 (P<0.01)] 4 [F(1,49)=1.64 (P=0.2)] 5 [F(1,49)=12.24 (P<0.01)] 6 [F(1,49)=1.43 (P=0.24)] 7 [F(1,49)=3.18 (P=0.08)] 2

P<0.01 P<0.01

150 100

3

50 0 HR-v

HR-cort

HR-T2-v

HR-T2-cort

LR-v

LR-cort

LR-T2-v

LR-T2-cort

Fig. 2. The influence of exposition to aversive context and corticosterone injection on GRs expression in brain structures of HR and LR rats. Data are shown as means + SEM. 1 Group effect, 2 drug effect, 3 fear effect, 4 group × drug interaction, 5 group × fear interaction, 6 drug × fear interaction, and 7 group × drug × fear interaction. Rats not exposed to aversive context: LR-v, low-anxiety rats given vehicle (n = 6); LR-cort, low-anxiety rats given corticosterone (n = 5); HR-v, high-anxiety rats given vehicle (n = 6); and HR-cort, high-anxiety rats given corticosterone (n = 8). Rats exposed to aversive context: LR-T2-v, low-anxiety rats given vehicle (n = 7); LR-T2-cort, low-anxiety rats given corticosterone (n = 9); HR-T2-v, high-anxiety rats given vehicle (n = 8); and HR-T2-cort, high-anxiety rats given corticosterone (n = 9).

3. Results 3.1. Behavioral data (Table 1) ANOVA revealed significant differences in the freezing duration between the first and second fear sessions: there was a group effect [F(1,15) = 65.39 (P < 0.01)], a time effect [F(1,15) = 7.79 (P = 0.01)], and no group × time interaction effect [F(1,15) = 0.68 (P = 0.42)]. Post hoc tests revealed a longer freezing duration in the HR-T1 group than in the LR-T1 group (P < 0.01). In the second fear session (T2), ANOVA showed significant differences between the HR and LR rats: a group effect [F(1,30) = 11.59 (P < 0.01)], a group × drug interaction effect [F(1,30) = 5.14 (P < 0.05)], and no drug effect [F(1,30) = 3.80 (P = 0.06)]. Post hoc tests revealed a longer freezing

duration in the HR-T2-v rats than in the LR-T2-v rats (P < 0.01). Post hoc comparisons also showed a significant decrease in the freezing duration of HR-T2-cort rats relative to that of HR-T2-v rats (P < 0.05). 3.2. GRs immunostaining (Fig. 2) ANOVA showed statistically significant differences between groups with respect to the density of cells expressing GRs in Cg1, the M2, and the DG (Fig. 2). In Cg1, the M2 and the DG, post hoc analysis revealed a lower expression level of GRs in the HR-T2-v group than in the LR-T2-v group (P < 0.01). In the LR-v group there was a lower density of GRs immunoreactive cells than in the LR-T2v group: Cg1 (P < 0.05), M2 area and DG (P < 0.01). The expression

A. Wisłowska-Stanek et al. / Neuroscience Letters 533 (2013) 17–22

level of GRs in the M2 and DG was higher in the HR-T2-cort group than in the HR-cort group (P < 0.01), and the expression level of GRs was higher in the HR-T2-cort group than in the HR-T2-v group in Cg1 (P < 0.05), the M2 area and the DG (P < 0.01). The expression of GRs was also higher in the M2 and DG in the LR-T2-cort group than in the LR-cort (P < 0.01). The HR-T2-cort and LR-T2-v groups had a higher expression of GRs in the M2 area than the LR-T2-cort group did (P < 0.05 and P < 0.01, respectively). 3.3. Correlation analysis In the HR group, a correlation analysis revealed a significant negative relationship between the freezing time during the T2 session and the expression of GRs in the DG [r = (−)0.69, P = 0.01] and Cg1 [r = (−)0.74, P < 0.01]. 4. Discussion Our study shows that after a second exposure to an aversive context (i.e., the extinction session), the LR rats had a higher expression level of GRs in Cg1, the M2 area and the DG than the HR rats did (LR-T2-v vs. HR-T2-v group). The pretreatment of HR rats with corticosterone enhanced the expression of GRs to the level found in LR rats. Importantly, corticosterone alone did not change the expression of GRs in the control rats that were not exposed to context-related aversive stimuli. The immunocytochemical effects were accompanied by a corticosterone-induced decrease in freezing time in the HR rats. The present results confirm earlier published findings that were recorded after the first testing session of a conditioned fear test [15]. We showed a higher expression of GRs in the DG and in the M2 area in LR rats compared with HR rats. However, we also found a higher expression of GRs in the BLA of HR rats than in the LR group [15]. It is noteworthy that although the three-way ANOVA performed in the current study did not reveal statistically significant differences between the analyzed groups in the BLA, the two-way ANOVA (i.e., the statistical analysis that included only the groups of rats that were exposed to the T2 session – second exposition to aversive context) showed a significantly higher expression of GRs in the BLA in the HR-T2-v group than in the LR-T2-v animals (P < 0.01). We also analyzed the behavior of HR and LR rats and the expression levels of GRs after a fear conditioning test, two extinction sessions, and a second conditioned fear training and re-testing that occurred 8 days after the second extinction session (i.e., in a model of extinction-based therapy of anxiety disorders) [16]. In HR rats, we found an increase in the expression of GRs immunoreactivity in the M2 area and in the DG region of the hippocampus 1.5 h after the re-test. Taken together, our current findings indicate that pretreatment of HR animals with corticosterone induces similar adaptive changes to those previously found after repetitive exposure of rats to an aversive context (i.e., extinction procedure) [16]. Our behavioral observations are consistent with clinical data showing that glucocorticosteroids administered before therapeutic sessions potentiate the effects of behavioral therapy in individuals with PTSD and phobias [5]. Moreover, cortisol treatment (10 mg per day) reduced the symptoms of traumatic memories in PTSD patients [6]. The different patterns of GRs expression in the two groups of animals may be the reason behind the different behavioral patterns in a challenging situation. Our previous studies clearly showed that HR and LR rats differ in their responsiveness to context-related aversive stimuli. The HR rats exhibit a more passive response strategy that is characterized by a longer freezing duration and less aversive ultrasonic vocalization (20–22 kHz band) when compared with LR rats [14]. We also found that 10 min

21

after a fear-conditioning test session, the HR group had a lower concentration of plasma corticosterone when compared with the LR rats [14]. One can assume that the higher levels of plasma corticosterone in LR animals may contribute to the more active coping strategy of this group. We also determined that LR and HR rats did not differ with respect to corticosterone levels under basal conditions [13]. In this context, it is noteworthy that GRs in the DG and the dorsal subregions of the medial prefrontal cortex participate in the negative control of the HPA activity and play an important role in aversive memory consolidation [8]. Previously, we found that in the LR group, in contrast to the HR group, there was a selective and significant increase in the level of aversive context-induced c-Fos activity in the parvocellular neurons of the paraventricular hypothalamic nucleus, the brain area where CRF is synthesized. These data suggest a stronger activation of the stress axis by the aversive context in LR rats, followed by elevated plasma levels of corticosterone. It is also striking that in LR rats, c-Fos protein expression was selectively increased in the DG [12]. In the present study, we observed that the behavioral effect of a decrease in freezing in the HR group after corticosterone pretreatment was accompanied by the increased expression of GRs in the DG. The biological significance of the described phenomenon (an increase in GRs expression) is not entirely clear; however, it can be considered, along with the activation of the DG and the prefrontal cortex (c-Fos study), as another coping mechanism to handle a threatening stimulus (note the negative correlation between GRs expression and anxiety-like behavior in the HR rats). The data suggest an inhibitory role of the prefrontal cortex in the process of actively coping with stressful events (as in the LR group) and underscore an important role of the of GRs activation in BLA in the promoting conditioned fear responses. It cannot be excluded with certainty, however that the differences in GRs expression are not the basis of the anxiety behavior but the result of neural response to the fear stress. In agreement with the current results, some clinical data suggest that deficits in the functioning of the HPA axis could be related to a stronger predisposition to the development of PTSD [3]. For example, patients who developed PTSD had significantly lower levels of urinary cortisol than individuals who experienced the same trauma but did not develop PTSD [4]. 5. Conclusions The present results suggest that HR animals may have deficits in the stress-related expression of GRs in the prefrontal cortex and the DG. Furthermore, pretreatment with corticosterone increases the expression of GRs, thus normalizing fear-controlled animal behavior. Acknowledgements This study was supported by statutory Grant No. 50100312043 from the Institute of Psychiatry and Neurology and by Grant No. 0440/B/P01/2009/36 from the Ministry of Science and Higher Education (ML), Warsaw, Poland. 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.neulet. 2012.11.012. References [1] J. Blundell, C.A. Blaiss, D.C. Lagace, A.J. Eisch, C.M. Powell, Block of glucocorticoid synthesis during re-activation inhibits extinction of an established fear memory, Neurobiology of Learning and Memory 95 (2011) 453–460.

22

A. Wisłowska-Stanek et al. / Neuroscience Letters 533 (2013) 17–22

[2] L.A. Brotto, B.B. Gorzalka, A.M. Barr, Paradoxical effects of chronic corticosterone on forced swim behaviours in aged male and female rats, European Journal of Pharmacology 424 (2001) 203–209. [3] H. Cohen, Z. Kaplan, M.A. Matar, U. Loewenthal, N. Kozlovsky, J. Zohar, Blunted HPA axis response to stress influences susceptibility to posttraumatic stress response in rats, Biological Psychiatry 59 (2006) 1208–1218. [4] D.L. Delahanty, A.J. Raimonde, E. Spoonster, Initial posttraumatic urinary cortisol levels predict subsequent PTSD symptoms in motor vehicle accident victims, Biological Psychiatry 48 (2000) 940–947. [5] D.J. de Quervain, D. Bentz, T. Michael, O.C. Bolt, B.K. Wiederhold, J. Margraf, F.H. Wilhelm, Glucocorticoids enhance extinction-based psychotherapy, Proceedings of the National Academy of Sciences of the United States of America 108 (2011) 6621–6625. [6] D.J. de Quervain, J. Margraf, Glucocorticosteroids for the treatment of posttraumatic stress disorder and phobias: a novel therapeutic approach, European Journal of Pharmacology 583 (2008) 365–371. [7] E. Geuze, G.A. van Wingen, M. van Zuiden, A.R. Rademaker, E. Vermetten, A. Kavelaars, G. Fernández, C.J. Heijnen, Glucocorticoid receptor number predicts increase in amygdala activity after severe stress, Psychoneuroendocrinology 37 (2012) 1837–1844. [8] J.P. Herman, H. Figueiredo, N.K. Mueller, Y. Ulrich-Lai, M.M. Ostrander, D.C. Choi, W.E. Cullinan, Central mechanisms of stress integration: hierarchical circuitry controlling hypothalamo-pituitary-adrenocortical responsiveness, Frontiers in Neuroendocrinology 24 (2003) 151–180. [9] J.P. Herman, R. Spencer, Regulation of hippocampal glucocorticoid receptor gene transcription and protein expression in vivo, Journal of Neuroscience 18 (1998) 7462–7473. [10] W.B. Hoover, R.P. Vertes, Anatomical analysis of afferent projection to the medial prefrontal cortex in the rat, Brain Structure and Function 212 (2007) 149–179. [11] K.M. Hurley, H. Herbert, M.M. Moga, C.M. Saper, Efferent projection of infralimbic cortex of the rat, Journal of Comparative Neurology 308 (1991) 249–276. [12] M. Lehner, E. Taracha, A. Skórzewska, P. Maciejak, A. Wisłowska-Stanek, M. ´ ´ A. Płaznik, Behavioral, immunocytochemZienowicz, J. Szyndler, A. Bidzinski, ical and biochemical studies in rats differing in their sensitivity to pain, Behavioural Brain Research 171 (2006) 189–198. [13] M. Lehner, Central mechanisms responsible for individual response to fear stimuli, Doctoral thesis, Institute of Psychiatry and Neurology, Warsaw, Poland, 2007. ´ [14] M. Lehner, E. Taracha, A. Skórzewska, D. Turzynska, A. Sobolewska, P. Maciejak, ´ ´ A. Wisłowska-Stanek, A. Płaznik, Expression J. Szyndler, A. Hamed, A. Bidzinski, of c-Fos and CRF in the brains of rats differing in the strength of a fear response, Behavioural Brain Research 188 (2008) 154–167. ´ [15] M. Lehner, E. Taracha, P. Maciejak, J. Szyndler, A. Skórzewska, D. Turzynska, A. ´ ´ A. Płaznik, Sobolewska, A. Wisłowska-Stanek, A. Hamed, A. Bidzinski, Colocalisation of c-Fos and glucocorticoid receptor as well as of 5-HT1A and glucocorticoid receptor immunoreactivity-expressing cells in the brain structures of low and high anxiety rats, Behavioural Brain Research 200 (2009) 150–159.

[16] M. Lehner, A. Wisłowska-Stanek, E. Taracha, P. Maciejak, J. Szyndler, A. ´ ´ ´ A. Sobolewska, A. Hamed, A. Bidzinski, A. Płaznik, Skórzewska, D. Turzynska, The expression of c-Fos colocalisation of c-Fos and glucocorticoid receptors in brain structures of low and high anxiety rats subjected to extinction trials and re-learning of a conditioned fear response, Neurobiology of Learning and Memory 92 (2009) 535–543. [17] M. Lehner, A. Wisłowska-Stanek, E. Taracha, P. Maciejak, J. Szyndler, A. ´ ´ ´ A. Sobolewska, A. Hamed, A. Bidzinski, A. Płaznik, Skórzewska, D. Turzynska, The effects of midazolam and d-cycloserine on the release of glutamate and GABA in the basolateral amygdala of low and high anxiety rats during extinction trial of a conditioned fear test, Neurobiology of Learning and Memory 94 (2010) 468–480. [18] G. Paxinos, C.H. Watson, The Rat Brain in Stereotaxic Coordinates, California Academic Press, San Diego, 1998. [19] S.L. Rauch, P.J. Whalen, L.M. Shin, S.C. McInerney, L.M. Macklin, N.B. Lasko, S.P. Orr, R.K. Pitman, Exaggerated amygdala response to masked facial stimuli in posttraumatic stress disorder: a functional MRI study, Biological Psychiatry 47 (2000) 769–776. [20] C. Sandi, C. Venero, C. Guaza, Novelty-related rapid locomotor effects of corticosterone in rats, European Journal of Neuroscience 8 (1996) 794–800. [21] L.M. Shin, P.J. Whalen, R.K. Pitman, G. Bush, M.L. Macklin, N.B. Lasko, S.P. Orr, S.C. McInerney, S.L. Rauch, An fMRI study of anterior cingulate function in posttraumatic stress disorder, Biological Psychiatry 50 (2001) 932–942. ´ ´ [22] A. Skórzewska, A. Bidzinski, M. Lehner, D. Turzynska, A. Sobolewska, A. Hamed, ´ The effects of acute corticosterone adminisJ. Szyndler, P. Maciejak, A. Płaznik, tration on anxiety, endogenous corticosterone, and c-Fos expression in the rat brain, Hormones and Behavior 52 (2007) 317–325. ´ ´ [23] A. Skórzewska, A. Bidzinski, M. Lehner, D. Turzynska, A. Wisłowska-Stanek, A. ´ The effects of acute Sobolewska, J. Szyndler, P. Maciejak, E. Taracha, A. Płaznik, and chronic administration of corticosterone on rat behavior in two models of fear responses, plasma corticosterone concentration, and c-Fos expression in the brain structures, Pharmacology Biochemistry and Behavior 85 (2006) 522–534. [24] E.A. Stone, M. Egawa, B.S. McEwen, Novel effect of chronic corticosterone treatment on escape behavior in rats, Behavioral and Neural Biology 50 (1988) 120–125. [25] A. Wisłowska-Stanek, M. Lehner, A. Skórzewska, P. Maciejak, J. Szyndler, D. ´ ´ Turzynska, A. Sobolewska, A. Płaznik, Effects of d-cycloserine and midazolam on the expression of the GABA-A alpha-2 receptor subunits in brain structures of fear conditioned rats, Behavioural Brain Research 225 (2011) 655–659. [26] A. Wisłowska-Stanek, M. Lehner, A. Skórzewska, P. Maciejak, J. Szyndler, D. ´ ´ A. Sobolewska, A. Płaznik, Turzynska, Corticosterone attenuates conditioned fear response and potentiates the expression of GABA-A receptor alpha-2 subunits in the brain structures of rats selected for high anxiety, Behavioural Brain Research 235 (2012) 30–35.