Lateral hypothalamic involvement in feeding elicited from the ventral pallidum

Abstract

Intense feeding can be elicited by injections of the GABA(A) receptor antagonist bicuculline into the medial ventral pallidum (VPm), a basal forebrain structure anatomically interposed between two other feeding-related brain regions, the nucleus accumbens shell and the lateral hypothalamus (LH). To determine whether the VPm effects changes in feeding behavior through actions on the LH, we examined feeding following unilateral injections of bicuculline into the VPm made either ipsilateral or contralateral to a unilateral excitotoxic lesion of the LH in nondeprived rats. We found that lesions of the LH significantly attenuated feeding induced from the ipsilateral VPm, as compared to sham-operated controls. In striking contrast, unilateral LH lesions significantly potentiated the feeding response elicited by injections of bicuculline into the contralateral VPm. The 'ipsilateral-contralateral disruption' design we used makes it extremely unlikely that our findings could have resulted from nonspecific effects of the lesions. These results suggest that the LH is causally involved in mediating the ingestive effects produced by activation of the VPm, and provide an important insight into the functional circuitry by which basal forebrain structures control food intake in mammals.