- Email: [email protected]
P.4.11 Higher histamine synthesis and release in inbred Roman high versus low avoidance rats: a histaminergic hypothesis
S88
Addiction: towards new drug targets
ethanol (1 g/kg) or WIN 55,212-2 was administered for 5 days, from PND 28 to PND 32. Such early ethanol exposure decreased (−28% p < 0.05) spontaneous alcohol consumption at adulthood. In contrast, their spontaneous alcohol intake increased (+37% p < 0.05) when C57BL/6J mice had been treated with WIN 55,212-2 at adolescence. In DBA/2J mice, which spontaneously avoid alcohol at adult age, the latter treatment did not significantly affect this behavioural trait. In contrast, early alcohol intake at adolescence regularly increased their spontaneous alcohol consumption under free-choice conditions at adulthood. This augmentation ranged between +34% and +94% (p < 0.001), depending on the dose and duration of early ethanol administration. No changes in 5-HT1A G protein coupling efficacy were generally observed in animals which had been exposed to alcohol at adolescence, except in C57BL/6J mice with an induced decrease in alcohol intake at adulthood (see above) for which 5-carboxamidotryptamine exhibited a 3-fold increased potency (p < 0.05) to enhance [35 S]GTP-g-S binding in the hippocampus. These results show that early ethanol and/or cannabis consumption can affect ethanol preference at adulthood. The differences between C57BL/6J and DBA/2J mice indicate that such induced modulations of alcohol intake are under genetic control. The change in 5-HT1A receptor coupling suggests that the critical influence of gene– environment interactions on alcohol preference/avoidance at adulthood may depend-in part-on serotoninergic mechanisms. This research has been supported by grants from INSERM, IREB and MILDT. Reference(s) [1] Grant, B.F., Dawson, D.A., 1998, Age of onset of drug use and its association with DSM-IV drug abuse and dependence: results from the National Longitudinal Alcohol Epidemiologic survey. J. Subst. Abuse 10: 163–173. [2] Kelai, S., Hanoun, N., Aufrere, G., Beauge, F., Hamon, M., Lanfumey, L., 2006, Cannabinoid-serotonin interactions in alcohol-preferring vs. alcohol-avoiding mice. J. Neurochem. 99: 308–320.
P.4.11 Higher histamine synthesis and release in inbred Roman high versus low avoidance rats: a histaminergic hypothesis D. Moreno-Delgado1 ° , L. Gim´enez-Llort2 , A. Fern´andezTeruel2 , J. Ortiz1 . 1 Institut de Neuroci`encies (UAB), Bioquimica i Biologia Molecular, Barcelona, Spain;
2
Institut de Neuroci`encies (UAB), Psiquiatria i Medicina Legal, Barcelona, Spain Introduction: H3 receptor ligands can be considered for the symptomatic treatment of several pathologies like Alzheimer, Parkinson, schizophrenia and drug abuse. Vulnerability to addiction has been associated with impulsivity and novelty-seeking. The use of Roman rats, genetically selected for high or low active avoidance acquisition in the two-way shuttle box, is a well-established laboratory model for novelty-seeking and anxiety profiles. It has been described that Roman High Avoidance (RHA-I) and Roman Low Avoidance (RLA-I) rats differ in several dopaminergic targets such as cocaine response and D1/D3 density receptors specially in Nucleus Accumbens (NAc) [1], but differences in the histaminergic system has never been reported. Method: We have developed a very sensitive technique that led to determine simultaneously histamine synthesis and release using fresh rat brain miniprisms incubated with tritium-labelled histidine, purifying tritium-labelled histamine using high-performance liquid chromatography (HPLC). Using this technique we have described the effects of different molecular pathways regulating histamine synthesis and release like constitutively active H3 receptors [2] and protein kinases and phosphatases [3]. We dissected different brain areas: cortical lobes, hypothalamus, nucleus accumbens, striatum and hippocampus from RHA-I and RLA-I rats. Results: We determined, in blind assays, that RHA-I’s histamine synthesis and release is increased in two regions, hypothalamus and nucleus accumbens whereas in hippocampus, striatum and cortex remain unchanged in comparison with RLA-I. Histamine synthesis and release is increased in hypothalamus and nucleus accumbens in 11 RHA-I rats, in comparison with 6 RLA-I rats. However, histamine levels in hippocampus, striatum and cortex are similar. Table 1.
Hypotalamus Nucleus Accumbens Hippocampus Striatum Cortex
Synthesis RLA-I
RHA-I
Release RLA-I
RHA-I
99.2±12.3 100.0±9.0 100.6±12.4 100.0±12.5 100.0±6.2
163.5±15.2* 163.6±32.6* 112.2±21.4 105.6±13.8 108.9±7.4
100.0±13.4 100.0±11.6 99.9±18.6 100.0±23.0 100.0±9.7
189.7±19.1* 178.1±32.2* 95.7±15.7 100.3±17.7 117.1±16.4
Results are normalized to % synthesis or release of RLA. Results are expressed means±SEM. *p < 0.05 vs RLA-I, unpaired t-student test.
Conclusion: Taking into account that: (1) extracellular histamine inhibits dopamine synthesis through histamine H3 heteroreceptors; (2) RHA-I rats have higher dopamine responses than RLA-I rats, but higher basal dopamine levels have not been described; we hypothesize that in
Addiction: towards new drug targets RHA-I basal levels of dopamine could be reduced by higher extracellular histamine acting on inhibitory H3 receptors. Stimulated dopamine responses may override in RHA-I rats would then override histaminergic inhibition of dopamine basal neurons. Supported by grants from the “Ministerio de Ciencia y Tecnolog´ıa” (SAF2003-03480), DGR (2005SGR-00885), (SAF2006-08240). Reference(s) [1] Guitart-Masip, M, et al., 2006, Divergent anatomical pattern of D1 and D3 binding and dopamineand cyclic AMP-regulated phosphoprotein of 32 kDa mRNA expression in the Roman rat strains: Implications for drug addiction. Neuroscience 3; 142(4): 1231–1243. [2] Moreno-Delgado, D., et al., 2006, Constitutive activity of H3 autoreceptors modulates histamine synthesis in rat brain through the cAMP/PKA pathway. Neuropharmacology 51(3): 517–523. [3] Moreno-Delgado, D, et al., 2007, Phosphatases regulate histamine synthesis in rat brain. Neuroscience 12; 150(3): 616–624. P.4.12 The role of serotonin in memory-related cortices for cocaine-induced place preference and hyperlocomotion C. Muller1 ° , M.E. Pum2 , R.J. Carey3 , J.P. Huston2 . Institute of Psychiatry, MRC-SGDP-Center, London, United Kingdom; 2 Institute of Physiological Psychology, University of Duesseldorf, Duesseldorf, Germany; 3 VA Medical Center, SUNY Upstate Medical University, Syracuse, USA
1
Human neuroimaging studies showed widespread activation of memory-related cortical areas in response to psychostimulant drugs or drug cues [1]. The neurochemical nature of the cortical activation and its functional significance are little understood. However, there is evidence for a significant role of serotonin (5HT), which displays a dense cortical innervation [2]. In a previous study we found a significant increase in 5-HT activity after cocaine in the occipital and temporal cortices of rats [3]. However, its functional significance for the behavioral effects of cocaine is unclear. Objective: The aim of the present studies was to investigate the neurochemical effects of cocaine on 5-HT activity in memory-related cortical areas, such as the entorhinal (EC), perirhinal (PRC), and medial prefrontal cortex (mPFC) in rats. In a second step we aimed to determine the functional significance of a local 5-HT response for the locomotor activating and reinforcing effects of cocaine.
S89
Methods: We conducted in vivo microdialysis experiments in behaving rats measuring 5-HT in the PRC, EC, and mPFC, after application of cocaine (0, 5, 10, 20 mg/kg; i.p.). Then bilateral serotonergic lesions to either the EC, mPFC, or the occipital cortex (OccC), where we found a potent cocaine-induced 5-HT increase in a previous study [3], were applied using 5,7-dihydroxytryptamine (5,7-DHT). Animals were investigated for cocaine (10 mg/kg, i.p.)-induced conditioned place preference (CPP) and locomotor activity. Data were analyzed by ANOVAs and pre-planned comparisons using HSD or LSD tests. Results: Cocaine dose-dependently increased 5-HT levels in the PRC, EC, and mPFC, with a predominant peak 5-HT response mPFC>EC>>PRC. In the placepreference study, cocaine-induced CPP was evident in the animals receiving vehicle infusions into the mPFC (p < 0.05 vs. saline), EC (p < 0.05), or OccC (p < 0.05). However, following a 90% depletion of 5-HT from the mPFC or a 61% depletion of 5-HT from the EC, animals did not express conditioned preference for the cocainepaired compartment as compared to their vehicle control animals (p > 0.05). In contrast, the 78% 5-HT depletion of the OccC had no effect on the establishment of cocaine-induced conditioned place-preference (p < 0.05). The hyperlocomotor effects of cocaine were blocked by a 5,7-DHT lesion of the mPFC (p > 0.05 vs. saline), but not by EC or OccC lesions (p < 0.01 vs. saline). Conclusions: We conclude that (a) cocaine dosedependently increases 5-HT activity in cortical areas associated with learning and memory, and (b) that the elevation of 5-HT in the mPFC and the EC contributes to cocaine-induced conditioned place preference. These findings support a role of 5-HT in memory-related cortical areas in the mediation of cocaine’s behavioural effects. This work was supported by the research grant HU306/23-5 from the Deutsche Forschungsgemeinschaft, a NIDA grant DA R01 DA 05366-17, and a VA Merit Review grant. Reference(s) [1] Breiter, H.C., Gollub, R.L., Weisskoff, R.M. et al., 1997, Acute effects of cocaine on human brain activity and emotion. Neuron 19: 591–611. [2] M¨uller, C.P., Carey, R.J., Huston, J.P., De Souza Silva, M.A., 2007, Serotonin and psychpstimulant addiction: focus on 5-HT1A-receptors. Prog. Neurobiol. 81: 133– 178. [3] M¨uller, C.P., De Souza Silva, M.A., Huston, J.P., 2007, Double dissociating effects of sensory stimulation and cocaine on serotonin activity in the occipital and temporal cortex. Neuropharmacology 52: 854–862.
Addiction: towards new drug targets
ethanol (1 g/kg) or WIN 55,212-2 was administered for 5 days, from PND 28 to PND 32. Such early ethanol exposure decreased (−28% p < 0.05) spontaneous alcohol consumption at adulthood. In contrast, their spontaneous alcohol intake increased (+37% p < 0.05) when C57BL/6J mice had been treated with WIN 55,212-2 at adolescence. In DBA/2J mice, which spontaneously avoid alcohol at adult age, the latter treatment did not significantly affect this behavioural trait. In contrast, early alcohol intake at adolescence regularly increased their spontaneous alcohol consumption under free-choice conditions at adulthood. This augmentation ranged between +34% and +94% (p < 0.001), depending on the dose and duration of early ethanol administration. No changes in 5-HT1A G protein coupling efficacy were generally observed in animals which had been exposed to alcohol at adolescence, except in C57BL/6J mice with an induced decrease in alcohol intake at adulthood (see above) for which 5-carboxamidotryptamine exhibited a 3-fold increased potency (p < 0.05) to enhance [35 S]GTP-g-S binding in the hippocampus. These results show that early ethanol and/or cannabis consumption can affect ethanol preference at adulthood. The differences between C57BL/6J and DBA/2J mice indicate that such induced modulations of alcohol intake are under genetic control. The change in 5-HT1A receptor coupling suggests that the critical influence of gene– environment interactions on alcohol preference/avoidance at adulthood may depend-in part-on serotoninergic mechanisms. This research has been supported by grants from INSERM, IREB and MILDT. Reference(s) [1] Grant, B.F., Dawson, D.A., 1998, Age of onset of drug use and its association with DSM-IV drug abuse and dependence: results from the National Longitudinal Alcohol Epidemiologic survey. J. Subst. Abuse 10: 163–173. [2] Kelai, S., Hanoun, N., Aufrere, G., Beauge, F., Hamon, M., Lanfumey, L., 2006, Cannabinoid-serotonin interactions in alcohol-preferring vs. alcohol-avoiding mice. J. Neurochem. 99: 308–320.
P.4.11 Higher histamine synthesis and release in inbred Roman high versus low avoidance rats: a histaminergic hypothesis D. Moreno-Delgado1 ° , L. Gim´enez-Llort2 , A. Fern´andezTeruel2 , J. Ortiz1 . 1 Institut de Neuroci`encies (UAB), Bioquimica i Biologia Molecular, Barcelona, Spain;
2
Institut de Neuroci`encies (UAB), Psiquiatria i Medicina Legal, Barcelona, Spain Introduction: H3 receptor ligands can be considered for the symptomatic treatment of several pathologies like Alzheimer, Parkinson, schizophrenia and drug abuse. Vulnerability to addiction has been associated with impulsivity and novelty-seeking. The use of Roman rats, genetically selected for high or low active avoidance acquisition in the two-way shuttle box, is a well-established laboratory model for novelty-seeking and anxiety profiles. It has been described that Roman High Avoidance (RHA-I) and Roman Low Avoidance (RLA-I) rats differ in several dopaminergic targets such as cocaine response and D1/D3 density receptors specially in Nucleus Accumbens (NAc) [1], but differences in the histaminergic system has never been reported. Method: We have developed a very sensitive technique that led to determine simultaneously histamine synthesis and release using fresh rat brain miniprisms incubated with tritium-labelled histidine, purifying tritium-labelled histamine using high-performance liquid chromatography (HPLC). Using this technique we have described the effects of different molecular pathways regulating histamine synthesis and release like constitutively active H3 receptors [2] and protein kinases and phosphatases [3]. We dissected different brain areas: cortical lobes, hypothalamus, nucleus accumbens, striatum and hippocampus from RHA-I and RLA-I rats. Results: We determined, in blind assays, that RHA-I’s histamine synthesis and release is increased in two regions, hypothalamus and nucleus accumbens whereas in hippocampus, striatum and cortex remain unchanged in comparison with RLA-I. Histamine synthesis and release is increased in hypothalamus and nucleus accumbens in 11 RHA-I rats, in comparison with 6 RLA-I rats. However, histamine levels in hippocampus, striatum and cortex are similar. Table 1.
Hypotalamus Nucleus Accumbens Hippocampus Striatum Cortex
Synthesis RLA-I
RHA-I
Release RLA-I
RHA-I
99.2±12.3 100.0±9.0 100.6±12.4 100.0±12.5 100.0±6.2
163.5±15.2* 163.6±32.6* 112.2±21.4 105.6±13.8 108.9±7.4
100.0±13.4 100.0±11.6 99.9±18.6 100.0±23.0 100.0±9.7
189.7±19.1* 178.1±32.2* 95.7±15.7 100.3±17.7 117.1±16.4
Results are normalized to % synthesis or release of RLA. Results are expressed means±SEM. *p < 0.05 vs RLA-I, unpaired t-student test.
Conclusion: Taking into account that: (1) extracellular histamine inhibits dopamine synthesis through histamine H3 heteroreceptors; (2) RHA-I rats have higher dopamine responses than RLA-I rats, but higher basal dopamine levels have not been described; we hypothesize that in
Addiction: towards new drug targets RHA-I basal levels of dopamine could be reduced by higher extracellular histamine acting on inhibitory H3 receptors. Stimulated dopamine responses may override in RHA-I rats would then override histaminergic inhibition of dopamine basal neurons. Supported by grants from the “Ministerio de Ciencia y Tecnolog´ıa” (SAF2003-03480), DGR (2005SGR-00885), (SAF2006-08240). Reference(s) [1] Guitart-Masip, M, et al., 2006, Divergent anatomical pattern of D1 and D3 binding and dopamineand cyclic AMP-regulated phosphoprotein of 32 kDa mRNA expression in the Roman rat strains: Implications for drug addiction. Neuroscience 3; 142(4): 1231–1243. [2] Moreno-Delgado, D., et al., 2006, Constitutive activity of H3 autoreceptors modulates histamine synthesis in rat brain through the cAMP/PKA pathway. Neuropharmacology 51(3): 517–523. [3] Moreno-Delgado, D, et al., 2007, Phosphatases regulate histamine synthesis in rat brain. Neuroscience 12; 150(3): 616–624. P.4.12 The role of serotonin in memory-related cortices for cocaine-induced place preference and hyperlocomotion C. Muller1 ° , M.E. Pum2 , R.J. Carey3 , J.P. Huston2 . Institute of Psychiatry, MRC-SGDP-Center, London, United Kingdom; 2 Institute of Physiological Psychology, University of Duesseldorf, Duesseldorf, Germany; 3 VA Medical Center, SUNY Upstate Medical University, Syracuse, USA
1
Human neuroimaging studies showed widespread activation of memory-related cortical areas in response to psychostimulant drugs or drug cues [1]. The neurochemical nature of the cortical activation and its functional significance are little understood. However, there is evidence for a significant role of serotonin (5HT), which displays a dense cortical innervation [2]. In a previous study we found a significant increase in 5-HT activity after cocaine in the occipital and temporal cortices of rats [3]. However, its functional significance for the behavioral effects of cocaine is unclear. Objective: The aim of the present studies was to investigate the neurochemical effects of cocaine on 5-HT activity in memory-related cortical areas, such as the entorhinal (EC), perirhinal (PRC), and medial prefrontal cortex (mPFC) in rats. In a second step we aimed to determine the functional significance of a local 5-HT response for the locomotor activating and reinforcing effects of cocaine.
S89
Methods: We conducted in vivo microdialysis experiments in behaving rats measuring 5-HT in the PRC, EC, and mPFC, after application of cocaine (0, 5, 10, 20 mg/kg; i.p.). Then bilateral serotonergic lesions to either the EC, mPFC, or the occipital cortex (OccC), where we found a potent cocaine-induced 5-HT increase in a previous study [3], were applied using 5,7-dihydroxytryptamine (5,7-DHT). Animals were investigated for cocaine (10 mg/kg, i.p.)-induced conditioned place preference (CPP) and locomotor activity. Data were analyzed by ANOVAs and pre-planned comparisons using HSD or LSD tests. Results: Cocaine dose-dependently increased 5-HT levels in the PRC, EC, and mPFC, with a predominant peak 5-HT response mPFC>EC>>PRC. In the placepreference study, cocaine-induced CPP was evident in the animals receiving vehicle infusions into the mPFC (p < 0.05 vs. saline), EC (p < 0.05), or OccC (p < 0.05). However, following a 90% depletion of 5-HT from the mPFC or a 61% depletion of 5-HT from the EC, animals did not express conditioned preference for the cocainepaired compartment as compared to their vehicle control animals (p > 0.05). In contrast, the 78% 5-HT depletion of the OccC had no effect on the establishment of cocaine-induced conditioned place-preference (p < 0.05). The hyperlocomotor effects of cocaine were blocked by a 5,7-DHT lesion of the mPFC (p > 0.05 vs. saline), but not by EC or OccC lesions (p < 0.01 vs. saline). Conclusions: We conclude that (a) cocaine dosedependently increases 5-HT activity in cortical areas associated with learning and memory, and (b) that the elevation of 5-HT in the mPFC and the EC contributes to cocaine-induced conditioned place preference. These findings support a role of 5-HT in memory-related cortical areas in the mediation of cocaine’s behavioural effects. This work was supported by the research grant HU306/23-5 from the Deutsche Forschungsgemeinschaft, a NIDA grant DA R01 DA 05366-17, and a VA Merit Review grant. Reference(s) [1] Breiter, H.C., Gollub, R.L., Weisskoff, R.M. et al., 1997, Acute effects of cocaine on human brain activity and emotion. Neuron 19: 591–611. [2] M¨uller, C.P., Carey, R.J., Huston, J.P., De Souza Silva, M.A., 2007, Serotonin and psychpstimulant addiction: focus on 5-HT1A-receptors. Prog. Neurobiol. 81: 133– 178. [3] M¨uller, C.P., De Souza Silva, M.A., Huston, J.P., 2007, Double dissociating effects of sensory stimulation and cocaine on serotonin activity in the occipital and temporal cortex. Neuropharmacology 52: 854–862.