Influence of the limbic system on ovulation and on progesterone and estrogen formation in rabbit's ovary.

Abstract

Listen

Translate article

By using the New Zealand White rabbits with chronically implanted bipolar electrodes in the several parts of the brain, studies of the influences of electrical stimulation of the limbic system and the hypothalamus upon progesterone and estrogen formation in the ovary and ovarian progesterone output were carried out. Effects were studied through observations upon inducement of ovulation and upon incorporation of radioactivity into progesterone and estrogen (estradiold-estrone) by the ovarian homogenates in vitro with (1-14C) acetate.The implanted rabbits were primed with estradiol benzoate in oil (0.1mg s. c.) for 2 days prior to stimulation to ensure an estrous state. Electrical stimulation, consisting of monophasic square wave pulses, was delivered unilaterally for 30 min., 60 sec. on and 60 sec. off, 260-280μA, at 0.1 msec. duration, 60 cps. The results were as follows:1. Ovulation was induced by 260-280μA electrical stimulation of the hippocampus in the estrogen primed rabbits in the 20 out of 30 cases. Almost no, differences were observed between the effect of electrical stimulation of the dorsal and the ventral parts of the hippocampus. Similar results were observed. in the effects of stimulation upon the intermediate nucleus of the amygdala and the periventricular arcuate nucleus. The ovulation induced thereby was. blocked by bilateral lesions of the dorsal or the ventral fornix, by a massive lesion of the septum, or by a localized lesion of the periventricular arcuate nucleus including the adjacent regions. On the contrary, when the stria terminalis was damaged bilaterally, hippocampal stimulation still produced hemorrhagic follicles in the ovaries.2. Electrical stimulation of the hippocampus enhanced progesterone formation in the ovary more than that of the amygdala and the periventricular arcuate nucleus. But, it showed an unappreciable difference in estrogen formation. among these three regions. The ratio of (14C)-incorporated estrogen to (14C)-incorporated progesterone (E/P) showed a lower value in the hippocampus than in the other areas.In respect to progesterone labelling from (1-14C) acetate by the ovarian homogenates, the ovarian progesterone output and the E/P ratio, little difference was observed between the effect of electrical stimulation of the amygdala. and the periventricular arcuate nucleus of the hypothalamus including the posterior tuberal region. When the dorsal or the ventral fornix was damaged bilaterally, the synthesis of ovarian progesterone and estrogen and the ovarian progesterone output were lower than those of the control without regard to hippocampal stimulation. But in the animals with lesion in bilateral stria terminalis hippocampal stimulation retained the facilitatory effect upon the formation of progesterone and estrogen and the progesterone output. These findings may suggest that the effect of hippocampal stimulation upon the ovary was exerted through the fornix and the basal hypothalamus including the arcuate nucleus, and not through the stria terminalis.