Adrenergic and dopaminergic control of growth hormone secretion in urethan anesthetized adult male rats.
The effects of drugs which interfere with alpha-adrenergic and dopaminergic mechanisms, involved in GH and PRL secretion, have been analyzed in urethane anesthetized rats. Clonidine induced a dose-dependent release of GH (0.0032--0.1 mg/kg i.v.) as well as of PRL (0.032--1.0 mg/kg i.v.). The lowest dose of clonidine, when given into the third ventricle, provoked a very pronounced release of GH. Phentolamine, given intravenously, inhibited the clonidine-induced GH release in a dose-dependnet manner. L-Dopa administered intravenously and apomorphine administered intravenously or intraventricularly did not affect basal secretion of GH bu- produced a dose-dependnet inhibition of clonidine-induced GH release. Pimozide did not change basal GH secretion. Furthermore pimozide did not attenuate the inhibition of clonidine-induced GH secretion seen after apomorphine administration, however, it completely reversed apomorphine-induced PRL inhibition. These findings demonstrate that an alpha-adrenoceptor-mediated stimulatory mechanism is involved in GH and PRL secretion. An inhibitory dopaminergic mechanism is confirmed for PRL secretion and suggested for GH secretion.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D013006:Growth Hormone / Q000097:blood*; D007276:Injections, Intraventricular; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D011388:Prolactin / Q000097:blood; D051381:Rats; D013565:Sympatholytics / Q000494:pharmacology*; D013566:Sympathomimetics / Q000494:pharmacology*; D014520:Urethane
D013565:Sympatholytics; D013566:Sympathomimetics; D010868:Pimozide; D014520:Urethane; D007980:Levodopa; D011388:Prolactin; D013006:Growth Hormone; D003000:Clonidine; D001058:Apomorphine; D009638:Norepinephrine; D010646:Phentolamine