Anorectic effect of amylin is not transmitted by capsaicin-sensitive nerve fibers

Abdominal vagal and splanchnic afferents play an important role in the control of food intake in that they transmit various satiety signals to the central nervous system. Inasmuch as previous studies have shown that the anorectic effect of intraperitoneally injected amylin was not abolished by subdiaphragmatic vagotomy, the aim of the present study was to elucidate the role of splanchnic afferents in mediating amylin's anorectic effect after intraperitoneal injection. Rats were pretreated intraperitoneally with the neurotoxin capsaicin, which destroys primary sensory (vagal and splanchnic) afferents. Sham-treated rats served as control. Capsaicin-pretreatment had no influence on the anorectic effects of amylin (5 microg/kg) and the related peptide, calcitonin gene-related peptide (CGRP; 5 microg/kg), in 24-h food-deprived rats. Abolition of cholecystokinin's (3 microg/kg) anorectic effect agrees with previous studies and confirmed the effectiveness of the capsaicin pretreatment. In conclusion, the anorectic effects of intraperitoneally injected amylin and CGRP are not mediated by capsaicin-sensitive primary sensory neurons. Both anorectic peptides are, therefore, most likely to act within the central nervous system. Previous studies suggest that the relevant receptors might be located in neurons of the area postrema-nucleus of the solitary tract region.