Differential effects of amylin and salmon calcitonin on neuropeptide gene expression in the lateral hypothalamic area and the arcuate nucleus of the rat

The pancreatic peptide hormone amylin (AMY) and the AMY receptor agonist salmon calcitonin (sCT) reduce short-term food intake in rats primarily by activating neurons located in the circumventricular area postrema. In the present study we analyzed the involvement of (an)orexigenic neuropeptides expressed in the lateral hypothalamic area (LHA) and in the arcuate nucleus in mediating the AMY and sCT-induced suppression of food intake. By using semiquantitative in situ hybridization 120 min after intraperitoneal injection of AMY or sCT (50 mug/kg), orexin mRNA levels were decreased in LHA by AMY or sCT treatment. Moreover, sCT significantly suppressed the orexigenic melanin concentrating hormone in LHA, whereas mRNA levels of neuropeptide Y, cocaine and amphetamine regulated transcript, agouti-gene-related protein and proopiomelanocortin were unaffected by either treatment. In conclusion, the anorexigenic effect of AMY/sCT might be mediated by the observed reduced expression of orexigenic neuropeptides in the LHA. (C) 2003 Published by Elsevier Science Ireland Ltd.