We investigated the effect of centrally administered pituitary adenylate cyclase activating polypeptide (PACAP) on feeding in rats, and the involvement of hypothalamic neuropeptide gene expression using in situ hybridization. lntracerebroventricular injection of PACAP (1000 pmol/rat) significantly decreased food intake in a dose-dependent manner. In PACAP-treated rats, neuropeptide Y (NPY) mRNA levels in the arcuate nucleus and galanin mRNA levels in the paraventricular nucleus increased, and corticotropin-releasing hormone (CRH) mRNA levels in the paraventricular nucleus decreased. In rats fasted for 72 h, NPY mRNA levels increased, and CRH mRNA levels decreased, but galanin mRNA levels were unchanged. These results indicate that the anorectic function of PACAP is not mediated by NPY or CRH, and that PACAP increases galanin synthesis.