New benzamide-derived 5-HT3 receptor antagonists which prevent the effects of ethanol on extracellular dopamine, and fail to reduce voluntary alcohol intake in rats

A set of substituted benzamides, characterized by the presence of a bulky quinolizidine moiety, were subjected to binding assays for 5-HT3 and D2 receptors on membranes obtained from the bovine area postrema ([3H]-GR65630) and the rat striatum ([3H]-spiperone) respectively. These benzamides resulted unsuitable for the recognition of D2 receptors, while a few of them, devoid of 5-HT4 receptor activity, had consistent affinity for central 5-HT3 receptors, inhibiting also potently the ethanol-induced dopamine efflux from the mesolimbic dopamine terminal region. However they failed in attenuating voluntary alcohol consumption in rats, as observed with several other chemically unrelated 5-HT3 antagonists. Thus the 5-HT3-mediated inhibition of alcohol-induced striatal release of dopamine by substituted benzamides is not a requisite for affecting ethanol intake.