Comparison of feeding suppression by the anorexigenic hormones neuromedin U and neuromedin S in rats.

We compared the central mechanisms of feeding suppression by the anorexigenic hormones neuromedin U (NMU) and neuromedin S (NMS) in rats. I.c.v. injection of either NMU or NMS dose dependently decreased 3-h food intake during the first quarter of a dark period. Pretreatment involving i.c.v. injection of a specific anti-NMS IgG blocked the suppression of food intake induced by i.c.v.- and i.p.-injected leptin, but anti-NMU IgG elicited no blockade. Quantitative PCR analysis revealed that i.c.v. injection of NMU or NMS caused a dose-dependent increase in CRH and proopiomelanocortin mRNA expression in the paraventricular nucleus (PVN) and arcuate nucleus (Arc) respectively. In tissue cultures of the Arc, secretion of α-melanocyte-stimulating hormone was stimulated by NMU and NMS, with more potent stimulation by NMS. The time-course curves of the increase in neuronal firing rate in Arc slices in response to NMU and NMS showed almost the same pattern, with a peak 10-15 min after treatment, whereas the time-course curves for the PVN slices differed between NMU and NMS. These results suggest that NMS and NMU may share anorexigenic effects, depending on physiological conditions.