Dual Action of Norepinephrine in the Control of Gonadotropin Release

Abstract

A role for catecholamines in the regulation of ovulation was first implicated when blockade of α-adrenergic receptors prevented ovulation in rabbits while infusion of norepinephrine (NE) into the third ventricle was able to induce ovulation (Sawyer et al., 1947; Sawyer, 1952). Likewise, in the rat, administration of α-adrenergic antagonists blocked ovulation suggesting that on the afternoon of proestrus a critical period exists during which time the hypothalamus becomes “activated” to secrete some gonadotropin-releasing factor (Everett et al., 1949; Everett and Sawyer, 1950). Since then a great deal of work has been done supporting an excitatory role for NE in the regulation of luteinizing hormone (LH) release and/or luteinizing hormone-releasing hormone((LHRH) (Barraclough and Wise, 1982; Ramirez et al., 1984). More recently, the possibility of an inhibitory role for NE In the control of LH release has been raised when it was found that infusion of NE into the third ventricle of ovariectomized (ovx) rats inhibited LH release (Gallo and Drouva, 1979). This chapter will briefly review the evidence of the dual role of NE in the regulation of LH release.