Administration of the 5-HT2C receptor antagonist SB-242084 into the nucleus accumbens blocks the expression of ethanol-induced behavioral sensitization in Albino Swiss mice.

Behavioral sensitization to the stimulating effect of ethanol (EtOH) or other drugs, which can be observed in mice as an increase in locomotor activity after repeated administration, has been associated with neuroadaptations within the dopaminergic mesolimbic pathway. in the nucleus accumbens (NAc), an afferent region of the mesolimbic pathway, dopamine (DA) release can be modulated by serotonergic 2C receptors (5-HT2C(R)). the aim of the present study was to evaluate the function of 5-HT2C(R) in the expression of EtOH-induced behavioral sensitization in Albino Swiss mice with various levels of sensitization to EtOH. in the four experiments that we performed, the mice were given saline or 2.2 g/kg EtOH daily for 21 days. Based on their locomotion on day 21, the EtOH-pretreated mice were assigned to one of two groups, highly sensitized or weakly sensitized to the stimulating effect of EtOH. in each experiment, 2 weeks after the 21-day treatment (withdrawal period), the mice were submitted to four pharmacological challenges of two drug treatments each. the mice in experiments 1 and 2 received two i.p. injections, whereas the mice in experiments 3 and 4 received an intra-NAc administration followed by an i.p. injection. the challenges were: saline+saline; saline+EtOH; SB-242084 (a 5-HT2C(R) antagonist; 0.5, 1.0 or 2.0 mg/kg i.p. or 1.0 or 2.0 mu g/side intra-NAc)+EtOH; and SB-242084 (0.5, 1.0 or 2.0 mg/kg i.p. or 1.0 or 2.0 mu g/side intra-NAc)+saline. At all tested doses, i.p. administration of SB-242084 did not affect the stimulating effect of EtOH in the highly sensitized mice. However, when delivered by intra-NAc administration, SB-242084 reduced (at 1.0 mu g/side) or completely blocked (at 2.0 mu g/side) the expression of EtOH-induced behavioral sensitization in the highly sensitized mice. These findings suggest that the expression of behavioral sensitization to the stimulating effect of EtOH depends on accumbal 5-HT2C(R) activity. (C) 2011 IBRO. Published by Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Associacao Fundo de Incentivo a Pesquisa (AFIP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo, Dept Psicobiol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psicobiol, São Paulo, BrazilCNPq: CNPq-371877/2008-3FAPESP: FAPESP-2008/07203-6Web of Scienc