EFFECTS OF ISOLATION OF MEDIAL BASAL HYPOTHALAMUS ON PITUITARY-ADRENAL AND PITUITARY-OVARIAN FUNCTIONS

A modification of the Halász-Pupp neurosurgical knife was used in two groups of female rats to completely or partially (anterior cuts) isolate the medial basal hypothalamus (MBH) from adjacent central nervous system. A scries of experiments was performed over a period of approximately 6 months to determine effects on several aspects of pi-tuitary-adrenal and pituitary-ovarian functions. Plasma levels of corticosterone, obtained under a variety of conditions, were used as an indirect index of adrenoeortieotropin (ACTH) secretion. Vaginal smears, ovarian histology, and weights of ovaries and uteri were used to assess gonadotropin sccrction. The most conspicuous effect of complete MBH isolation on the pituitary-adrenal system was elimination of the diurnal peak in nonstress plasma corticosterone levels. Such isolation was compatible with a normal response to 3-min ether stress; the response to immobilization stress was present, though significantly reduced. Dexamethasone administered subcutaneously caused complete suppression of non-stress plasma corticosterone levels in all rats. Interruption of anterior connections of MBH did not measurably influence these aspects of ACTH secretion. Both complete and anterior cuts were associated with abnormal pituitary-ovarian function, but there were differences between the effects of these two procedures. Whereas constant vaginal diestrus and ovarian and uterine atrophy occurred frequently in rats with complete cuts, the persistent vaginal cstrous syndrome was more common in rats with anterior cuts. © 1969 S. Karger AG, Basel.