Abstract
Summary
The present experiments were carried out to determine the effects of phenoxybenzamine (an alpha adrenergic blocking agent) upon ovulation and the concentration of LH in the blood of ovariectomized and proestrus rats. Ovulation was blocked when phenoxybenzamine (20 mg/kg) was administered prior to the assumed critical period of LH release. This effect could be overcome by treatment with HCG (20 IU) during the critical period. Treatment with propranolol or MJ 1999 (beta adrenergic blocking agents) had no effect on ovulation. Phenoxybenzamine injections for 2 days (20 mg/kg/day) or for 8 days (10 mg/kg/day) was shown to be ineffective in preventing the rise in plasma LH levels that occurs in ovariectomized controls. A single injection of phenoxybenzamine before the critical period in cycling rats also was shown to have no significant effect on the level of LH present in the blood during the afternoon of proestrus. These results suggest that phenoxybenzamine may be acting directly on the ovary to prevent ovulation and that alpha adrenergic receptors located in the ovary may play an important role in the ovulatory process.
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