The presence of adrenergic nerves and smooth muscle in the mammalian ovary has prompted an investigation of the role of this neuromuscular complex in the ovulatory process. The in vitro perfused rabbit ovary preparation was used to study the effects of adrenergic agents on ovulation. Ovaries were exposed to norepinephrine (NE) at four dose levels (6 × 10-6M, 10-7M, 10-8M, and 10-9M). Ovulation occurred in a dose-dependent fashion with 10-6M NE resulting in the greatest ovulatory efficiency (64.7%). Addition of NE to ovaries treated with the minimal effective dose of human chorionic gonadotropin (hCG) (5 IU) led to an increase (59.9%) in ovulatory efficiency when compared to that of the ovaries treated with hCG alone (25.9%) but was not associated with an increase when compared to that of the ovaries treated with NE alone at the same dose level. Phenoxybenzamine (PBZ), an irreversible α-receptor antagonist, or phentolamine (POA), a competitive α-adrenergic inhibitor, was added to perfused ovaries to determine if either agent could block hCG- or NE-induced ovulation. Neither PBZ (10-6M) nor POA (10-5M) had any effect on NE (10-8M)-induced ovulation. The addition to the perfusate of either PBZ or POA significantly reduced ovulatory efficiency associated with hCG stimulation (p < 0.02) but did not completely block ovulation. Determination of the stage of maturity of ovulated ova and follicular oocytes demonstrated that more than 85% of ova exposed to NE remained in the germinal vesicle stage. Only those ova exposed to hCG consistently achieved metaphase I or II. A high percentage of degenerated ova was observed in both ovulated ova and follicular oocytes exposed to POA. A positive correlation was observed between ovarian edema and ovulatory efficiency (p < 0.005). These experiments indicate that adrenergic receptors can contribute to follicle rupture. However, the failure of PBZ and POA to inhibit NE- or hCG-induced ovulation indicates that adrenergic receptors are not essential mediators of the ovulatory process.
ASJC Scopus subject areas
- Obstetrics and Gynecology