ACTIVATION OF THE RAT MELANIN-CONCENTRATING HORMONE NEURONS BY VENTROMEDIAL HYPOTHALAMIC-LESIONS

The occurrence of a melanin-concentrating hormone-like peptide (MCH) w as previously reported in the lateral hypothalamus of the rat. The seq uence of this peptide was determined but its role as well as its regul ation remain unclear. In the present study, we examined the effects of minor electrolytic lesions of the ventromedial nuclei (VMN) on MCH ne urons by using immunocytochemical and in situ hybridization procedures . We report that VMN lesions resulted in (1) a clear elevation in the number and staining intensity of MCH immunoreactive perikarya and fibr es, (2) a significant increase in the level of hybridocytochemical sig nal obtained with an oligonucleotide probe complementary to rMCH mRNA. These data provide evidence for a role of VMN in modulating the MCH g ene and peptide expression.