Further studies on the effects of lesions in the rostral hypothalamus on gonadotropin secretion in the female rhesus monkey (Macaca mulatta).

Bilateral radiofrequency lesions were stereotaxically placed in the rostral hypothalamus of four adult female rhesus monkeys. These lesions resulted in extensive destruction of the ventromedial preoptic-anterior hypothalamic area (POA-AHA) and included the suprachiasmatic nucleus as well as, with the exception of one animal, the organum vasculosum of the lamina terminalis. In three of these four animals, gonadotropin surges similar to those observed before surgery were elicited in response to either a spontaneous increment in serum estrogen concentration or an estradiol benzoate injection. This stimulatory action of estradiol on LH and FSH release was not demonstratable in the remaining lesioned animal, but estradiol benzoate injections also failed to elicit a gonadotropin discharge in one of a series of five normal control animals. These findings fail to support the view that destruction of the ventromedial POA-AHA in this species compromises the ability of the hypothalamicohypophysial apparatus to respond to the positive feedback action of estradiol. The diurnal variation in serum cortisol concentration was not interrupted by placement of the lesions in the ventromedial POA-AHA.