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

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.