Evidence of NPYY5 receptor involvement in food intake elicited by orexin Ain sated rats

Intracerebroventricular (icv) injections of orexin A stimulate feeding in s ated rats:. Since neuropeptide Y is a potent orexigenic peptide and orexin- containing neurons are morphologically linked with NPY-producing neurons in the hypothalamus, we evaluated the functional relationship between the two orexigenic peptides. The results show that whereas it was ineffective on i ts own, a selective NPY Y5 receptor antagonist, injected icy 15 min. before orexin A significantly suppressed orexin A-induced feeding. Since previous investigations demonstrated that an NPY Y1 receptor antagonist also inhibi ts feeding induced by orexin A, the current results further underscore the existence of a functional link between orexin and NPY producing neurons as the orexin network appears to be capable of influencing NPYergic signaling through Y1 and Y5 receptors to stimulate feeding. (C) 2000 Elsevier Science Inc. All rights reserved.