ABSTRACT
The discovery of neuropeptides provides insights into the regulation of physiological processes. The precursor for the neuropeptide neuromedin U contains multiple consensus sequences for proteolytic processing, suggesting that this precursor might generate additional peptides. We performed immunoaffinity chromatography of rat brain extracts and consequently identified such a product, which we designated neuromedin U precursor-related peptide (NURP). In rat brain, NURP was present as two mature peptides of 33 and 36 residues. Radioimmunoassays revealed NURP immunoreactivity in the pituitary, small intestine, and brain of rats, with the most intense reactivity in the pituitary. Intracerebroventricular administration of NURP to both male and female rats robustly increased plasma concentrations of prolactin but not of other anterior pituitary hormones. In contrast, NURP failed to stimulate prolactin release from dispersed anterior pituitary cells. Pretreatment of rats with bromocriptine, a dopamine receptor agonist, blocked the prolactin-releasing activity of NURP. In rats pretreated with the antagonist sulpiride, intracerebroventricular administration of NURP did not increase plasma prolactin concentrations more than administration of saline. These data suggest that NURP induces prolactin release by acting indirectly on the pituitary; dopamine from the hypothalamus, which inhibits prolactin release, may be involved in this activity of NURP.
Subject(s)
Neuropeptides/metabolism , Prolactin/biosynthesis , Protein Precursors/metabolism , Amino Acid Sequence , Animals , Chromatography, High Pressure Liquid , Female , Immunohistochemistry , Male , Neuropeptides/chemistry , Neuropeptides/isolation & purification , Protein Precursors/chemistry , Proteolysis , Rats , Receptors, Dopamine/metabolismABSTRACT
Neuromedin U (NMU) activates two NMU receptors (NMUR1 and NMUR2) and is a useful antiobesity drug lead. We report discovery of a hexapeptide agonist, 2-thienylacetyl-Trp1-Phe(4-F)2-Arg3-Pro4-Arg5-Asn6-NH2 (4). However, the NMUR1 selectivity and serum stability of this agonist were unsatisfactory. Through a structure-activity relationship study focused on residue 2 of agonist 4, serum stability, and pharmacokinetic properties, we report here the discovery of a novel NMUR1 selective hexapeptide agonist 7b that suppresses body weight gain in mice.
Subject(s)
Peptides/pharmacology , Receptors, Neurotransmitter/agonists , Weight Gain/drug effects , Animals , Calcium/metabolism , Drug Evaluation, Preclinical/methods , Drug Stability , Humans , Male , Peptides/blood , Peptides/pharmacokinetics , Rats, WistarABSTRACT
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.
