Involvement of alpha-adrenergic and GABAergic mechanisms in growth hormone secretion induced by central somatostatin in rats.
Brain opiatergic, alpha-adrenergic and GABAergic mechanisms are known to play a stimulating role in growth hormone (GH) secretion in the rat. Plasma GH levels were increased by intracerebroventricular (i.c.v.) injection of somatostatin-14 (SRIF-14, 5 micrograms/rat) in conscious rats. GH release induced by i.c.v. SRIF-14 was blunted by either intravenous (i.v.) injection of phenoxybenzamine (500 micrograms/100 g b. wt.), an alpha-adrenergic blocker, or picrotoxin (150 micrograms/100 g b. wt.), a GABA antagonist, in the rat. On the other hand, i.v. injection of naloxone (125 micrograms/100 g b. wt.), an opiate antagonist, did not affect GH release induced by i.c.v. SRIF-14. These findings suggest that alpha-adrenergic and GABAergic mechanisms but not opiatergic mechanisms are involved in central SRIF-induced GH secretion in the rat.
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D004723:Endorphins / Q000502:physiology; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D004723:Endorphins; D013004:Somatostatin; D005680:gamma-Aminobutyric Acid; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone