Role of Neuromedin S in Plasma Testosterone and Cortisol Concentrations in Male Adult Rhesus Monkey (Macaca mulatta)

Neuromedin S (NMS), a 36 amino acid peptide structurally related to neuromedin U, identified in rat brain as ligand for the G protein-coupled receptor FM4/TGR-1, also termed neuromedin U receptor type-2 (NMU2R). Its central expression is restricted to the suprachiasmatic nucleus, and involved in the regulation of dark light rhythms and suppression of food intake. Stimulatory role of NMS on hypothalamic pituitary gonadal axis (HPG) is reported in rodents. Yet the potential contribution of NMS in the control of reproductive axis in higher primates remains unexplored. In the present study, the effect of peripheral administration of NMS on testosterone and cortisol secretion in the adult male rhesus monkey was evaluated. Four adult male Rhesus monkeys were used for this study. Three different doses of NMS (20nmol, 40nmol and 60nmol) were injected through a teflon cannula implanted in saphenous vein. Blood samples were collected 45 min before and 120 min after NMS administration at 15 min intervals. The plasma concentration of testosterone and cortisol were determined by using specific assay systems. The NMS induced testosterone secretion was significantly (P<0.05) increased at 60 and 40nmol compared to 20nmol. The highest response was observed at a dose of 60nmol. A dose dependent stimulatory role of NMS was noticed in these animals. NMS administration showed a significant (P<0.05) decrease in cortisol secretion at 40nmol and 60nmol doses while non significant (P>0.05) difference was observed at 20nmol. NMS has stimulatory role in testosterone secretion whereas its effect was inhibitory on cortisol secretion. In conclusion, the present study suggests the involvement of neuromedin S in the regulation of hypothalamic pituitary gonadal and adrenal axis in non human primates.