DIFFERENTIAL-EFFECTS OF FLUOXETINE ON ISOPRENALINE-STIMULATED WATER-INTAKE IN ETHANOL-TREATED RATS - A ROLE FOR BETA-ADRENOCEPTORS

We examined the effects of subchronic (4 days) administration of the 5-hydroxytryptamine (5-HT) re-uptake inhibitors, fluoxetine, fluvoxamine and zimelidine and the noradrenaline-uptake inhibitor, desipramine, on isoprenaline-induced water drinking in rats treated with ethanol. These rats demonstrated significant increases in water drinking as compared to control rats that had received only i.p. injections of distilled water (P < 0.01). Administration of fluoxetine (5-20 mg/kg daily i.p., for 4 days) dose-dependently decreased water intake as compared to that of rats treated with ethanol only. In contrast, fluvoxamine, zimelidine (10 mg/kg i.p.) and desipramine (5 mg/kg i.p.) produced no significant effects on water intake. Pretreatment of animals with spiperone, methysergide, ritanserin, zacopride and BRL 43694A, together with fluoxetine, failed to reverse the inhibitory effect of the latter on isoprenaline-stimulated water intake. The results of the present study indicate that the action of fluoxetine on isoprenaline-stimulated water drinking in ethanol-treated rats may be mediated by an action on beta-adrenoceptors.