FUNCTIONAL INTERACTIONS BETWEEN MELANIN-CONCENTRATING HORMONE, NEUROPEPTIDE-Y, AND ANORECTIC NEUROPEPTIDES IN THE RAT HYPOTHALAMUS

A growing body of evidence indicates that a number of peptides express ed in the mammalian hypothalamus are involved in the regulation of foo d intake and energy balance. Among these, melanin-concentrating hormon e (MCH) and neuropeptide Y (NPY) are potent appetite stimulants, where as alpha-melanocyte-stimulating hormone (alpha-MSH), neurotensin, and glucagon-like peptide (GLP)-1(7-36) amide have appetite-suppressing pr operties. However, the functional interactions between pathways involv ing these neuropeptides remain incompletely understood. In the current study, we describe the functional interactions between orexigenic (ap petite-stimulating: MCH and NPY) and anorectic (appetite-suppressing: alpha-MSH, neurotensin, and GLP-1) peptides after intracerebroventricu lar (ICV) administration in the rat. The ICV administration of GLP-1 c ompletely prevents the orexigenic effects of both MCH and NPY. However , ICV administration of alpha-MSH prevents only the orexigenic effect of MCH, as we have previously shown, but does not prevent the effect o f NPY on food intake. Similarly, ICV administration of neurotensin pre vents only the orexigenic effect of MCH, but does not prevent the appe tite-stimulating effect of NPY. Thus, our study suggests that the func tional interactions between these neuropeptides are specific, although the underlying mechanisms are as yet unexplored.