Association of leptin receptor (OB-Rb), NPY and GLP-1 gene expression in the ovine and murine brainstem.

Appetite-related neuropeptide systems have not been studied extensively 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), neuropeptide Y (NPY) and glucagon-like peptide-1 (GLP-1) gene expression in the ovine brainstem. Leptin receptor mRNA was localized to the spinal trigeminal tract and nucleus, nucleus of the solitary tract (NTS), area postrema and dorsal motor nucleus of the vagus. NPY gene expression was abundant in the ovine medulla, occurring in two bilateral 'bands' that encompassed the NTS region and ran ventrolaterally. GLP-1 mRNA was confined largely to the NTS. The distribution of OB-Rb mRNA overlapped with that of NPY and GLP-1 gene expression, suggesting the possibility of interaction between leptin and these brainstem neuropeptide systems. However, in an extension of earlier work, co-expression studies in the murine brainstem revealed only a small number of neurons that expressed both NPY and leptin receptor mRNA, despite the widespread and abundant expression of the former. Thus the majority of NPY synthesis in the brainstem may not be directly regulated by leptin. The sheep brainstem had similar anatomical distribution of OB-Rb, NPY and GLP-1 gene expression to the rodent, consistent with a role for this region in peripheral leptin feedback signaling and brainstem-hypothalamo communication.