Acute effects of adrenergic receptor blocking drugs and neuroleptic agents on pulsatile discharges of luteinizing hormone in the ovariectomized rat.

Blood samples were taken every 5 min for a 3-h period from ovariectomized (OVX) adult rats bearing chronic venous catheters. After 1 h of sampling, an experimental drug was injected through the sampling catheter. The neuroleptics, chlorpromazine and haloperidol, blocked pulsatile discharges of luteinizing hormone (LH) in some animals, for periods of 65-120 min, as did the alpha-adrenergic receptor blockers, phenoxybenzamine and phentolamine. Pimozide, a more specific dopaminergic blocking agent, had less effect, while neither the beta-adrenergic receptor blocker, propranolol, nor the control treatments had any influence on the pulsatile LH patterns. The temporal pattern of inhibition of pulsatile discharges of LH by these drugs is more rapid than the inhibition caused by estrogen treatment in the OVX rat. These results suggest the presence of alpha, but not beta, adrenergic elements in the pulsatile mode of LH release in the OVX rat. They do not support the presence of dopaminergic elements, but neither do they conclusively deny it.