Caudal hindbrain participation in the suppression of feeding by central and peripheral bombesin

We have previously demonstrated that bombesin (BBS) infused into the fourth cerebral ventricle in rats suppressed feeding at doses 10-1,000 times less than those required after lateral ventricular administration. These results suggest that centrally administered BBS acts in the caudal hindbrain to suppress food intake. To investigate the participation of caudal hindbrain structures in fourth-ventricular BBS-induced suppression of feeding, we made lesions that destroyed the following: 1) area postrema (AP) and 2) and medial nucleus of the solitary tract (NST). Additionally, we examined the role of the AP/NST in the suppression of food intake after peripheral BBS administration. Our experiments revealed that lesions of the AP/NST abolished the suppression of food intake by fourth-ventricular BBS and attenuated the suppression of food intake by peripheral BBS. Lesions restricted to the AP attenuated the suppression of food intake by fourth-ventricular BBS but had no effect on suppression of intake by peripherally administered BBS. These results suggest that the NST may be a common neural substrate for the inhibition of food intake by both centrally and peripherally administered BBS.