Estrogen-induced gonadotropin surges in decerebrated female rhesus monkeys with medial basal hypothalamic peninsulae.

Hypothalamic peninsulae, posteriorly continuous with the brain stem, were produced in ovariectomized rhesus monkeys by aspiration of the cerebral hemispheres and all brain structures anterior and dorsal to the optic chiasm. These preparations were sustained for 52 to 60 h postoperatively by maintaining blood gases and pH within physiological limits and by supporting arterial blood pressure, when necessary, with infusions of rhesus monkey blood and norepinephrine. The sc injection of estradiol benzoate (EB) to such animals upon completion of the ablation procedure was followed 18-24 h later by unambiguous surges of serum LH and FSH with durations in the excess of 24 h. These findings are consonant with the view that the central components of the control system that initiates the preovulatory gonadotropin surge in the rhesus monkey are resident within the medial basal hypothalamic-hypophysial apparatus.