Activation of the rat melanin-concentrating hormone neurons by ventromedial hypothalamic lesions

The occurrence of a melanin-concentrating hormone-like peptide (MCH) was previously reported in the lateral hypothalamus of the rat. The sequence of this peptide was determined but its role as well as its regulation remain unclear. In the present study, we examined the effects of minor electrolytic lesions of the ventromedial nuclei (VMN) on MCH neurons 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 fibres, (2) a significant increase in the level of hybridocytochemical signal obtained with an oligonucleotide probe complementary to rMCH mRNA. These data provide evidence for a role of VMN in modulating the MCH gene and peptide expression.