DIFFERENTIAL-EFFECTS OF DELTORPHIN ON ARGININE AND GALANIN-INDUCED GROWTH-HORMONE SECRETION IN HEALTHY MAN

Recently we demonstrated the inhibitory action on Growth Hormone (GH) secretion of an opioid heptapeptide, deltorphin (DT), that is highly s elective in binding delta-opioid receptors. To investigate the possibl e mechanism leading to the decrease in GH secretion by specific activa tion of delta-opioidergic pathway in man, we compared, in normal subje cts, the effect of DT on GH secretion responses to two different GH se cretagogues, namely arginine (ARG) and galanin (GAL). DT completely bl unted the GH response to ARG, whereas it attenuated the GH response to GAL, but not at a statistically significant level. We suggest that th e specific activation of delta-opioid receptors in man may exert an in hibitory influence on GH secretion principally by modulating endogenou s hypothalamic somatostatin (SRIH) release.