[Role of hypothalamic monoamines in the regulation of gonadotropin secretion]

Experiments on rats were made to examine the time course of changes in the content of dopamine, noradrenaline and serotonin in different areas of the hypothalamus during the estrous cycle and the effects of local administration of monoamines to the nuclear formations of the hypothalamus on luteinizing hormone (LH) release in intact and ovariectomized female rats. The amplitude of circadian fluctuations in the monoamine level was demonstrated to depend on the phase of the estrous cycle, with the minimal values in the preovulatory period. The differences were detected in the pattern of the response of pituitary gonadotrophics to the administration of monoamines to the hypothalamus depending on the function of the sexual glands. It was noted that noradrenergic innervation of the preoptic area and dopaminergic innervation of the arcuate nucleus exert a stimulant effect on the preovulatory release of LH and that serotoninergic innervation of the indicated areas has an inhibitory effect on the same process. Estradial was demonstrated to have a modulatory action on the studied effects of monoamines. The data obtained indicate the involvement of noradrenaline, dopamine and serotonin in the control of cyclic secretion of LH in female rats.