Application of taste reactivity to study the mechanism of alcohol intake inhibition by the tachykinin aminosenktide.

Tachykinin NK-3 receptor agonists reduce alcohol intake in alcohol-preferring rats; the nucleus basalis magnocellularis (NBM) is highly sensitive to their effect. Tachykinins and their receptors are widely distributed in gustatory pathways and NK-3 receptor agonists have been reported to modify taste reactivity to salt solutions in rats. The present study evaluated whether the TK NK-3 receptor agonist aminosenktide (NH2-SENK) influences taste reactivity to ethanol solutions. Genetically selected Marchigian Sardinian alcohol-preferring (msP) rats were employed. In response to the intraoral infusion (0.8 ml in 1 min) of 10, 20, 40, or even 60% ethanol solution, ethanol-naive rats showed a large number of ingestive reactions and a much lower number of aversive reactions. Two min before the intraoral infusion of 10 or 40% ethanol, NH2-SENK was injected either into the lateral ventricle (LV) or into the NBM. Doses of NH2-SENK that markedly reduce alcohol intake, 125 ng/rat into the LV or 5 ng/site into the NBM, did not modify the ingestive reactions and, in some instances, reduced the aversive reactions to ethanol solutions in ethanol-naive rats. Injections of 125 ng/rat into the LV failed to modify taste reactions in ethanol-experienced rats. The present results show that msP rats have an innate hedonic evaluation of ethanol solutions, even of high concentration. Moreover, they indicate that reduction of ethanol intake induced by TK NK-3 receptor agonists in alcohol-preferring rats does not depend on influences on gustatory processes.