title: Neuropharmacological regulation of episodic growth hormone and prolactin secretion in the rat.
abstract: The effects on GH and PRL secretion of several pharmacological agents known to modify central neurotransmitter action were determined in unanesthetized male rats. Phenoxybenzamine, an alpha-adrenergic blocker (5 mg/kg iv), abolished episodic GH secretion and caused elevation of serum PRL levels. Propranolol, a beta-adrenergic blocker (5 mg/kg iv), had no effect on GH secretion and caused a small but significant depression in PRL levels. Parachlorophenylalanine methyl ester, an inhibitor of tryptophan hydroxylase (300-350 mg/kg ip), resulted in significant inhibition of GH pulsatile secretion and suppressed PRL levels. Methysergide hydrogen maleinate (25 mg/kg iv), a serotonin receptor antagonist, also inhibited GH secretion, but produced a transient stimulation in PRL levels. Atropine sulfate (2 mg/kg iv) caused significant suppression in GH secretion, but had no effect on PRL. Picrotoxin, a gamma-aminobutyric acid antagonist, in a subconvulsive dose of 1-3 mg/kg iv, also depressed GH episodic secretion but did not affect PRL levels. These results indicate that several neurotransmitters, i.e., norepinephrine, serotonin, acetylcholine, and gamma-aminobutyric acid, found in high concentration in the hypothalamus, influence GH and PRL secretion.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D010134:Fenclonine / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism*; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors*; D010507:Periodicity; D010643:Phenoxybenzamine / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D001285:Atropine; D010134:Fenclonine; D013006:Growth Hormone; D008784:Methysergide; D018377:Neurotransmitter Agents; D010643:Phenoxybenzamine; D010852:Picrotoxin; D011388:Prolactin; D011433:Propranolol