Specific neuroanatomical and neurochemical correlates of grooming and satiety effects of bombesin

Experiments characterized the behavioral effects of bombesin (BN) administered systemically (1-8 μg/kg; IP) or centrally at the nucleus tractus solitarius (NTS) and the nucleus accumbens (NA) (0.0001-1.0 μg/0.5 μl). The role of dopaminergic system(s) in the mediation of BN-induced behavioral effects in rats was also investigated. In the "satiety" paradigm, grooming and eating behaviors were monitored in 5-hr-food-deprived rats trained to take a portion of their daily food intake over the 20 min observation period. The elicitation of grooming and satiety appeared to be specific to BN administration at the NTS but not the NA. The dopaminergic system(s) did not appear to mediate the behavioral effects of BN intra NTS. The BN-induced grooming profile appeared to be paradigm independent although the baseline grooming profile was not. At the NTS, a dissociation of BN-induced grooming and satiety was evident on the basis of time-course and dose-effect. The similarity of the time-course of satiety induced by BN injected at the NTS and IP suggested that BN may mediate a physiological satiety signal at the NTS. Furthermore, since BN induced satiety 10⁴ more potently and 20% more efficaciously intra NTS than IP, the NTS may be a critical site for the action of BN on satiety.