Serotonin-3 receptor and ethanol-stimulated dopamine release in the nucleus accumbens

The present study was undertaken to examine the involvement of activation of 5-HT3 receptors in the rat nucleus accumbens (Acb) on the effects of ethanol-induced increases of dopamine (DA) using the selective agonist 1-(m-chlorophenyl)-biguanide (CPBG). Perfusion of CPBG through the microdialysis probe concentration-dependently (3.3-100 microM) enhanced the extracellular levels of DA in the Acb. Extracellular DA concentrations increased as high as 1000% of baseline. The CPBG-induced increases in DA levels were Ca++ dependent and inhibited by local perfusion with the 5-HT3 antagonist ICS 205-930 (100 microM). In addition, CPBG at high concentrations caused significant decreases in the extracellular levels of DA metabolites. Intraperitoneal (IP) injection of 1 g/kg ethanol produced no changes in extracellular DA levels in the Acb; coadministration of 1 g/kg ethanol (IP) and 5 microM CPBG (local) produced increases equal to 5 microM CPBG alone. Administration of 2 g/kg ethanol (IP) alone enhanced extracellular DA levels by approximately 60% above baseline, whereas local perfusion of 5 microM CPBG alone produced an increase of approximately 100% above baseline. The coadministration of 2 g/kg ethanol (IP) and 5 microM CPBG (local) enhanced DA levels by approximately 170% above baseline; this apparent additive enhancement was almost completely prevented when 100 microM ICS 205-930 was locally coperfused. Local administration of 3.3-100 microM CPBG did not alter the extracellular levels of serotonin or 5-hydroxyindoleacetic acid. The results support an involvement of 5-HT3 receptors in regulating DA release in the Acb, and also in mediating ethanol-induced DA release.(ABSTRACT TRUNCATED AT 250 WORDS)