EFFECTS OF CATECHOLAMINES ON GROWTH HORMONE(GH) SECRETION IN GRASS CARP (CTENOPHARYNGODONIDELLUS)

The effects of catecholamines on the growth hormone (GH) secretion in grass carp,were investigated. α-MPT (i. p, 50ug/gb·w and 5ug/gb·w) decreased significantly the GH levels in the serum of grass carp fingerling 6 hours post injection. 6-HODA of higher dose (i. p, 50ug/gb·w) decreased significantly the GH levels in the fingerlings 2 hours and 6 hours post injection, whereas 6-HODA of lower dose (i. p, 5ug/ gb·w) decreased significantly the GH levels in the fingerlings 2 hours post injection. APO (via dorsal aorta cannulae, 7.1 mg/Kgb·w and 12.5ing/Kgb·w) increased significantly the serum GH levels. NE (i. p, 50ug/gb·w) decreased significantly the GH levels in the serum of the fingerlings 2 hours, 6 hours and also 24 hours post injection. Intraperitoneal injections of β-adrenergic antagonist Propranolol (5 ug/gb·w) or α-adrenergic agonist Clonidine(5ug/gb·w) did not imposed any significant influences on the GH levels in the serum of the grass carp fingerling. The GH levels in the serum of grass carp fingerling injected i. p. with NE+Clonidine (50ug/gb·w, sug/gb·w) or NE+Propranolol (50ug/gb·w, 5ug/gb·w) were significantly higher than those injected with NE (50ug/gb·w) alone. It is indicated that catecholamines may be involved in the regulation of GH secretion in grass carp, and that NE can bind the β-adrenergic receptors to inhibit GH secretion, and bind the α adrenergic receptors to stimulate GH secretion in grass carp fingerling.