Bombesin-induced anorexia: sites of action in the rat brain

To determine the brain sites at which centrally injected bombesin (BBS) may act to suppress feeding behavior, this peptide (1.0 micrograms/0.3 microliter) was microinjected into one of twelve brain regions in 6 hr food deprived rats, and food intake was measured 45 min postinjection. Bombesin produced its strongest suppression of feeding (47-65%) when injected into hypothalamic areas, namely, the paraventricular, dorsomedial, ventromedial nuclei and lateral hypothalamus, and also when administered into the amygdala and the periaqueductal gray. Insensitive areas included the septum, ventral tegmental area and reticular formation. In contrast to these somewhat site-specific effects on feeding behavior, observation of BBS' effects on other behaviors revealed that, in all brain areas tested, there was a significant increase in grooming behavior and decrease in time spent resting and sleeping. In conjunction with high levels of BBS-like immunoreactivity and BBS receptors in the brain areas where injected BBS suppresses feeding, these results suggest that the effects of centrally administered BBS on feeding behavior may be mediated by multiple hypothalamic and extra-hypothalamic brain regions.