Cholecystokinin and bombesin in vagotomized or intact lean and obese rats: effects on neurotransmitters in brain.

Cholecystokinin (CCK) and Bombesin (BBS) are two neuropeptides which induce changes in monoamines in the brain after peripheral administration. A vagal mediation of these effects was investigated since the satiety responses to both peptides are affected differently by vagotomy. This work was performed on genetically obese and lean Zucker rats and on "cafeteria-fed" and lean Sprague-Dawley rats as the effects of the peptides are dissimilar in these different groups. Vagotomy either inhibited or potentiated the peptide-induced effects, or created new variations. With CCK, the inhibition occurred mainly in the serotonergic system and in the Zucker strain, while new effects appeared in the dopaminergic system of lean rats of both strains. With bombesin, vagotomy inhibited the effects in the dopaminergic system in all lean rats, while new effects were observed in the serotonergic system in the Zucker strain. These data enable the differentiation of the mechanisms of action of both peptides and their selective effects, according to the strain of rat and the presence or absence of obesity.