Capsaicin attenuates bombesin-induced suppression of food intake.

This study was conducted to evaluate the extent to which bombesin (BBS)-induced suppression of food intake relies on small, unmyelinated sensory neurons. Rats were pretreated intraperitoneally with capsaicin, a neurotoxin that destroys a subpopulation of small-diameter sensory neurons, and tested for suppression of food intake after intraperitoneal administration of 2, 4, 8, 16, and 32 micrograms/kg BBS. Capsaicin pretreatment attenuated suppression of food intake by BBS over a wide range of doses. The site of capsaicin action was not determined in this study. However, work by others indicates that vagal and nonvagal neural substrates participate in suppression of food intake by BBS. Afferents of both of these substrates are predominantly small and unmyelinated. Therefore, the deficits in BBS-induced suppression of food intake that we observed may reflect damage to both vagal and/or nonvagal neurons that participate in BBS-induced suppression of food intake.