Sulpiride injections in the lateral hypothalamus induce feeding and drinking in rats

Abstract

Amphetamine injections into the lateral hypothalamus inhibit feeding. This effect is blocked by local administration of neuroleptics, suggesting a role for dopamine in feeding inhibition. However, the type of dopamine receptor involved in satiety is not known. Therefore, we tested the effect of intrahypothalamic injections of sulpiride, a specific D2 receptor blocker, on amphetamine anorexia in food-deprived rats, and on spontaneous feeding and drinking in satiated rats. Sulpiride attenuated by 36% the anorexia produced by intrahypothalamic injections of amphetamine. In satiated rats, sulpiride (8 micrograms/0.5 microliter) elicited feeding (mean food intake after sulpiride: 5.4 g, and after vehicle 1.6 g, p less than 0.001), and drinking (mean water intake after sulpiride: 12.3 ml, and after vehicle: 0.9 ml, p less than 0.001). A dose response relationship was found between sulpiride dose and feeding or drinking. Sulpiride-induced drinking was observed in the absence of food, showing that it is not a postprandial phenomenon. These results suggest that hypothalamic D2 receptors might be involved in feeding and drinking regulation.