AREGU June 45/6

Michaud, David, Hymie Anisman, and Zul Merali. Capsaicin-sensitive fibers are required for the anorexic action of systemic but not central bombesin. Am. J. Physiol. 276 (Regulatory Integrative Comp. Physiol. 45): R1617–R1622, 1999.—Bombesin (BN) suppresses food intake in rats whether given centrally or systemically. Although the brain BNsensitive receptors are known to be essential for the anorexic effect of systemic BN, the mode of communication between the gut and the brain remains unclear. This study assessed whether the anorexic effect of systemic BN is mediated humorally or via neural circuits. Afferent neurons were lesioned using capsaicin (50 mg/kg sc) on postnatal day 2, and responses to BN were assessed during adulthood. Capsaicin treatment decreased body weight gain significantly from postnatal age 4–7 wk. Peripheral BN (4–16 μg/kg ip) dose dependently suppressed food intake in control animals. However, this effect was completely blocked in capsaicin-treated rats. In contrast to systemic effects, feeding-suppressant effects of centrally administered BN (0.01–0.5 μg icv) were not affected by capsaicin treatment. This research suggests that peripheral BN communicates with the brain via a neuronal system(s) whose afferent arm is constituted of capsaicin-sensitive C and/or Ad-fibers, whereas the efferent arm of this satietyand/or anorexia-mediating circuitry is capsaicin resistant.