Differential effects of a 5-HT2 receptor blocker on alcohol intake in rats selectively bred for high and low catecholamine responses to stress.

The effect of the selective 5-HT2 receptor blocker ritanserin on alcohol consumption was investigated in two strains of rats selectively bred for high and low catecholamine responses to stress. Rats were forced to drink a 5% alcohol solution for 10 days. For the subsequent six days, animals were injected subcutaneously with 2.5 mg/kg/2 ml ritanserin or vehicle only, and both a 5% solution of alcohol and water were presented to the animals. Ritanserin affected neither water nor total fluid intake. Furthermore, no effect of ritanserin on alcohol consumption could be demonstrated in high-responding rats, whereas in low-responding rats a very pronounced ritanserin-induced reduction in alcohol intake was observed. Results are discussed in terms of mediating effects of serotonergic neurons on mesolimbic dopaminergic reward systems related to drug addiction.