Norepinephrine Is a Possible Neurotransmitter Stimulating Pulsatile Release of Luteinizing Hormone-Releasing Hormone in the Rhesus Monkey*

TLDR

The study tested whether norepinephrine facilitates pulsatile luteinizing hormone‑releasing hormone (LHRH) release in conscious rhesus monkeys. A modified push‑pull perfusion technique was used to sample the stalk‑median eminence in ovariectomized females. LHRH and norepinephrine were released in synchronous pulses; local norepinephrine or methoxamine infusion stimulated LHRH, while intravenous prazosin suppressed it, supporting norepinephrine as a possible neurotransmitter for pulsatile LHRH release.

Abstract

The hypothesis that norepinephrine (NE) plays a facilitatory role in controlling the pulsatile release of LHRH was tested with a modified push-pull perfusion technique in conscious rhesus monkeys. The in vivo LHRH release in perfusate samples collected from the stalk-median eminence of ovariectomized females was pulsatile and synchronous with pulsatile LH release. Catecholamines measured in aliquots of perfusate samples revealed that in vivo NE release was also pulsatile and was synchronous with LHRH release. Local infusion of NE or methoxamine (an alpha 1-adrenergic stimulant) through a push cannula stimulated LHRH release, while iv injection of prazosin (an alpha 1-adrenergic blocker) suppressed LHRH release. It is concluded that NE is a possible neurotransmitter stimulating pulsatile LHRH release.