Acute XXXX and activation of the beta-adrenergic system exhibit synergistic inhibitory actions on @entity2124 ( @entity2124 ) releasing hormone-induced GH release.

@entity1169 @entity7704 @entity5482 @entity2124 @entity3044 @entity4854 @entity413
OBJECTIVE: Acute @entity4854 stimulates somatostatin (SRIH) release by the hypothalamus which, in turn, suppresses @entity2124 ( @entity2124 ) secretion from the anterior pituitary gland. Although it has been suggested that the cholinergic pathway mediates @entity413 -induced SRIH release, other regulatory systems have not been examined. Therefore, we investigated whether blocking or activating the beta-adrenergic pathway alters @entity413 -mediated inhibition of @entity2124 release. DESIGN AND METHODS: One set of experiments was performed with a beta-adrenergic antagonist, @entity1169 , and the other set with a beta-adrenergic agonist, @entity3044 . Each set of experiments was performed in ten healthy subjects and consisted of four tests. @entity5482 , a 100 microg @entity7704 bolus i.v. at 0 min; test 2, 100 g @entity413 orally at -30 min, followed by a 100 microg @entity7704 bolus at 0 min; test 3, after a 100 microg @entity7704 bolus i.v. at 0 min, a continuous infusion of @entity1169 (0.2 mg/kg) or @entity3044 (0.012 microg/kg) was administered between 0 and 120 min; test 4, after a 100 g @entity413 oral load at -30 min, and a 100 microg @entity7704 bolus i.v. at 0 min, a continuous infusion of @entity1169 (0.2 mg/kg) or @entity3044 (0.012 microg/kg) was administered between 0 and 120 min. Blood was drawn every 10 min from -30 min to 120 min to measure @entity2124 and @entity413 concentrations. RESULTS: Pretreatment with @entity413 significantly suppressed @entity7704 -induced @entity2124 secretion. @entity1169 infusion significantly increased the @entity7704 -induced @entity2124 secretion, but it did not block @entity413 -induced suppression of @entity2124 secretion. @entity3044 infusion alone significantly suppressed @entity7704 -induced @entity2124 secretion and augmented the inhibitory action of @entity413 on @entity2124 release. CONCLUSION: This study demonstrates that @entity413 -induced suppression of @entity7704 -stimulated @entity2124 release is independent of beta-adrenergic tone. Since previous data supports a role for SRIH in both @entity413 and beta-adrenergic suppression of @entity2124 release, the current results suggest that subsets of SRIH neurons are differentially responsive to these external cues. Therefore, a combined @entity413 and @entity3044 test may provide a useful assessment of hypothalamic somatostatinergic activity.
