Effects of acute ethanol administration on monoamine and metabolite content in forebrain regions of ethanol-tolerant and -nontolerant alcohol-preferring (P) rats.

The contents of dopamine (DA), serotonin (5-HT) and their metabolites in the frontal cortex, anterior striatum, nucleus accumbens and hypothalamus of alcohol-tolerant and -nontolerant rats of the alcohol-preferring P line were determined one hour after the IP administration of 2.5 g ethanol/kg body wt. Compared with saline-injected controls, nontolerant P-rats injected with ethanol had (a) 60% higher levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the frontal cortex; (b) 30-60% higher levels of DOPAC and HVA in the anterior striatum and nucleus accumbens; and (c) 20% higher levels of 5-HIAA in all three forebrain regions. In the tolerant group, the effects of IP ethanol on DOPAC and HVA were markedly attenuated or completely eliminated in these three forebrain regions. However, in the case of 5-HIAA, an attenuated response was observed only in the nucleus accumbens of the tolerant group. The IP administration of ethanol had little effect on the contents of DA or 5-HT in any of these three forebrain regions, with the exception that 5-HT levels were elevated in the anterior striatum of both the tolerant and nontolerant groups. In the hypothalamus, there were no significant differences for the contents of DA, 5-HT or their metabolites between the nontolerant or tolerant P rats after IP ethanol. The data indicate that both acute ethanol administration and chronic alcohol intake by the P line of rats alters certain DA and 5-HT systems that may be involved in the brain reward circuitry and in DA pathways involved in motor functions.