Stimulation by alpha-adrenergic mechanisms of the secretion of growth hormone-releasing factor (GRF) from perifused rat hypothalamus.
The possible involvement of adrenergic mechanisms in regulating the secretion of growth hormone (GH)-releasing factor (GRF) from the rat hypothalamus was examined in vitro with a perifusion system. A high potassium concentration (56 mM) stimulated GRF release from the hypothalamus. The infusion of clonidine (10(-4) M), an alpha 2-adrenergic stimulant, resulted in an increase in the spontaneous release of GRF. In the presence of propranolol (10(-5) M), a beta-adrenergic blocking agent, clonidine (10(-5) and 10(-4) M) stimulated GRF release more prominently in a dose-related manner, whereas propranolol (10(-5) and 10(-4) M) by itself did not affect the spontaneous GRF release. The stimulatory effect of clonidine (10(-4) M) on GRF release in the presence of propranolol was inhibited by yohimbine (10(-4) M), an alpha 2-adrenergic blocking agent. These findings suggest that alpha 2-adrenergic mechanisms play a role in stimulating GRF release from the hypothalamus in rats.
Kabayama
Y
Y
Kato
Y
Y
Murakami
Y
Y
Tanaka
H
H
Imura
H
H
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012636:Secretory Rate / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D013007:Growth Hormone-Releasing Hormone; D011433:Propranolol; D003000:Clonidine; D011188:Potassium