Abstract
Androgen-induced constant-estrous rats (50μg of testosterone propinate was subcutaneously injected at 5th day of age) were stimulated through implanted electrodes. Electrical stimulation (100Hz, 0.1msec, 100μA) was applied for 30min at 30sec period alternating with 30sec rest period. Immediately after the stimulation animals were anesthetized by ether and blood samples and anterior pituitary glands were taken for radioimmunoassay of gonadotropin. Results were as follows: 1) In the androgenized rats pituitary LH was slightly lower, but prolactin was higher than those of normal cycling rats. Pituitary FSH in the androgenized rats was almost equivalent to that in the 4-day cyclic rats. Serum FSH was lower in the androgenized rats, while serum LH was on the same level. 2) Electrical stimulation of the medial preoptic area increased serum LH and FSH, but decreased serum prolactin. The same tendency as induced by medial preoptic stimulation has been observed in the normal cycling rats. 3) Electrical stimulation of the medial part of the amygdala decreased pituitary LH, FSH and serum FSH, and did not increase serum LH. These changes were just the contrast of those found in normal cycling rats in which amygdaloid stimulation increased serum LH and FSH. 4) Hippocampal stimulation increased serum FSH, as was observed in 4-day cyclic rats. However, hippocampal stimulation slightly increased serum LH level in contrast to the change in normal cycling rats, in which the hippocampal stimulation never increases serum LH, but rather inhibits its increase with following to the medial preoptic stimulation. Furthermore, the weakening of inhibitory influence of the hippocampus on ovulation, which was induced by medial preoptic stimulation, was observed in androgenized rats.
In conclusion, when the function of the brain of androgenized rats was compared to that of normal cycling rats, quite a difference was observed in the amygdala and hippocampus rather than in the medial preoptic area.
