Abstract
Neuromedin S (NMS) is a neuropeptide identified as another endogenous ligand for two orphan G protein-coupled receptors, FM-3/GPR66 and FM-4/TGR-1, which have also been identified as types 1 and 2 receptors for neuromedin U structurally related to NMS. Although expression of NMS mRNA is found mainly in the brain, spleen, and testis, the distribution of its peptide has not yet been investigated. Using a newly prepared antiserum, we developed a highly sensitive radioimmunoassay for rat NMS. NMS peptide was clearly detected in the rat brain at a concentration of 68.3 ± 3.4 fmol/g wet weight, but it was hardly detected in the spleen and testis. A high content of NMS peptide was found in the hypothalamus, midbrain, and pons–medulla oblongata, whereas abundant expression of NMS mRNA was detected only in the hypothalamus. These differing distributions of the mRNA and peptide suggest that nerve fibers originating from hypothalamic NMS neurons project into the midbrain, pons, or medulla oblongata. In addition, abundant expression of type 2 receptor mRNA was detected not only in the hypothalamus, but also in the midbrain and pons–medulla oblongata. These results suggest novel, unknown physiological roles of NMS within the brainstem.
Highlights
Neuromedin S (NMS) is a neuropeptide originally isolated by our group from the rat brain as an additional endogenous ligand for neuromedin U (NMU) receptors types 1 (NMUR1) and 2 (NMUR2), which were previously identified as the orphan G protein-coupled receptors FM-3/GPR66 and FM-4/TGR-1, respectively (Mori et al, 2005)
NMS mRNA is expressed predominantly in the suprachiasmatic nucleus (SCN) of the hypothalamus, low-level expression of NMS mRNA is found in other hypothalamic nuclei, such as the arcuate nucleus (ARC), paraventricular nucleus (PVN), and supraoptic nucleus (SON; Mori et al, 2005)
The intra- and inter-assay variations were 3.1 and 3.8%, respectively. This antiserum had no cross-reactivity with rat NMU (Figure 1C) as well as neuropeptide Y, somatostatin, pituitary adenylate cyclase activating polypeptide, vasoactive intestinal polypeptide, calcitonin gene-related peptide, adrenocorticotropic hormone, α-melanocyte-stimulating hormone, and orexin-A, which are abundantly present in the hypothalamus
Summary
Neuromedin S (NMS) is a neuropeptide originally isolated by our group from the rat brain as an additional endogenous ligand for neuromedin U (NMU) receptors types 1 (NMUR1) and 2 (NMUR2), which were previously identified as the orphan G protein-coupled receptors FM-3/GPR66 and FM-4/TGR-1, respectively (Mori et al, 2005). NMS and NMU are structurally related peptides composed respectively of 36 and 23 amino-acid residues (Brighton et al, 2004; Mori et al, 2005). They have an identical C-terminal amidated seven-residue sequence that is essential for their agonist activity. In contrast to the mRNA distribution, the distribution of the NMS peptide in the brain has not yet been elucidated
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