The pharmacologic blockade of the circhoral mode of LH secretion in the ovariectomized rhesus monkey.

In ovariectomized rhesus monkeys, single injections into the right atrium of the neuroleptic drugs chlorpromazine and haloperidol or of the α-adrenergic blockers phentolamine and phenoxybenzamine were followed, within min, by an interruption in the circhoral pulsatile discharge of LH and a resultant fall in the plasma concentration of the hormone. This inhibition of LH secretion was usually sustained for some hr and was terminated by an abrupt resumption of the pulsatile secretory pattern. These responses were qualitatively indistinguishable from those previously reported to follow single injections of estradiol. In contrast, the p-adrenergic blocking agent propanolol or pentobarbital in anesthetic doses had no, or equivocal effects on the pulsatile pattern of LH discharge. Evidence is adduced in support of the view that these discharges of LH, as observed in ovariectomized monkeys, are the consequence of intermittant dopaminergic and/or nor-adrenergic signals to the LRF secreting cells of the hypothalamu...