EFFECTS OF NEUROMEDIN-B ON THE RAT PITUITARY-ADRENOCORTICAL AXIS

Adult male Wistar rats were treated for 2 days with s.c. injections of neuromedin-B (NMB)(3 or 9 mu g/rat/day). NMB administration did not a ffect adrenal weight, but it dose-dependently increased the volume of zona-fasciculata cells and the plasma concentration of corticosterone (B). The higher dose of NMB also markedly raised B output by adrenal s lices. The blood concentration of ACTH was enhanced, but the rise was statistically not significant. NMB (10(-10)/10(-6) M) did not alter ei ther basal or ACTH-stimulated B secretion by dispersed adrenocortical cells. These findings suggest that NMB exerts an indirect glucocortico id secretagogue effect on the rat adrenal cortex, which does not seem to be entirely mediated by the NMB-induced increase of pituitary ACTH release.