Effects of Muscarinic and Adrenergic Blockade on Growth Hormone Secretion Induced by Growth Hormone-Releasing Peptide-2 (GHRP-2) in Ovariectomized Ewes

This study was performed to investigate whether the blockade of cholinergic muscarinic and adrenergic pathways was involved in the GH-releasing effect of GH-releasing peptide-2 (GHRP-2) in ovariectomized ewes. Cholinergic muscarinic antagonist, atropine (0.2mg/kg, iv, 15min before GHRP-2 administration) blunted the GH secretion caused by GHRP-2 (12.5μg/kgBW). α-Adrenergic antagonist phentolamine (15μg/kgBW•min, infusion from -15 to 30min) did not affect the GH response to GHRP-2, and β-adrenergic antagonist propranolol (0.25mg/kgBW, iv, 15min before GHRP-2 administration) did not suppress the GHRP-2-induced GH release. These results showed that cholinergic muscarnic antagonist agent, atropine, exerts an inhibitory effect on GHRP-2-induced GH secretion in ovariectomized ewes.