Effect of dopamine, bombesin and cysteamine hydrochloride on plasma growth hormone response to synthetic growth hormone-releasing factor in rats.
In urethane anesthetized rats, an intracerebroventricular (icv) injection of 2 micrograms bombesin 5 min prior to the administration of synthetic human growth hormone-releasing factor (GRF) (1 microgram/kg, iv) inhibited plasma growth hormone (GH) response, while cysteamine hydrochloride (90 mg/kg, sc) administered 150 min beforehand depleted immunoreactive somatostatin content in the pituitary-stalk median eminence and consequently potentiated the response to GRF. Under the same experimental conditions, central injection of 1.89 micrograms (10(-8)M) dopamine hydrochloride or iv administration of L-DOPA (10 mg/kg) did not influence the subsequent plasma GH response to GRF. Results suggest indirectly that bombesin and cysteamine, but not dopamine, predominantly modulate somatostatin release from the hypothalamus.
Wakabayashi
I
I
Tonegawa
Y
Y
Shibasaki
T
T
Ihara
T
T
Hattori
M
M
Ling
N
N
D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D003543:Cysteamine / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007275:Injections, Intravenous; D007276:Injections, Intraventricular; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000378:metabolism
D010455:Peptides; D007980:Levodopa; D013004:Somatostatin; D003543:Cysteamine; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001839:Bombesin; D004298:Dopamine