ASSOCIATION OF LEPTIN RECEPTOR (OB-RB), NPY AND GLP-1 GENE-EXPRESSIONIN THE OVINE AND MURINE BRAIN-STEM

Appetite-related neuropeptide systems have not been studied extensivel y in the ruminant, although there have been a number of recent studies of the hypothalamus. Since some leptin signaling is integrated in the rodent brainstem, and leptin modulates neuropeptidergic activity, we now describe leptin receptor (long splice variant, OB-Rb), neuropeptid e Y (NPY) and glucagon-like peptide-1 (GLP-1) gene expression in the o vine brainstem. Leptin receptor mRNA was localized to the spinal trige minal tract and nucleus, nucleus of the solitary tract (NTS), area pos trema and dorsal motor nucleus of the vagus. NPY gene expression was a bundant in the ovine medulla, occurring in two bilateral 'bands' that encompassed the NTS region and ran ventrolaterally. GLP-1 mRNA was con fined largely to the NTS. The distribution of OB-Rb mRNA overlapped wi th that of NPY and GLP-1 gene expression, suggesting the possibility o f interaction between leptin and these brainstem neuropeptide systems. However, in an extension of earlier work, co-expression studies in th e murine brainstem revealed only a small number of neurons that expres sed both NPY and leptin receptor mRNA, despite the widespread and abun dant expression of the former. Thus the majority of NPY synthesis in t he brainstem may not be directly regulated by leptin. The sheep brains tem had similar anatomical distribution of OB-Rb, NPY and GLP-1 gene e xpression to the rodent, consistent with a role for this region in per ipheral leptin feedback signaling and brainstem-hypothalamo communicat ion. (C) 1998 Elsevier Science B.V. All rights reserved.