Effect of Hippocampal Stimulation on the Release of Gonadotropin

Abstract

The effect of hippocampal stimulation on the release of gonadotropin was studied in rats. The hippocampus was unilaterally stimulated by electrolytic deposition of iron from stainless steel unipolar electrodes. Stimulation of the ventral hippocampus (area CA3 or subiculum) prevented spontaneous o violation in proestrous rats and prevented ovulation induced by amygdaloid or preoptic stimulation in rats made to be persistently in estrus by continuous illumination. Stimulation of the dorsal hippocampus also prevented spontaneous ovulation. No effect on ovulation was observed after stimulation of other areas of the brain. The blockade of ovulation was overcome by injection of picrotoxin or by transection of the medial corticohypothalamic tract. Plasma levels of LH (as measured by the ovarian ascorbic acid depletion) were found significantly lower 3 hr after hippocampal stimulation in proestrous rats injected with progesterone. Also, the elevated plasma LH of ovariectomized rats was depressed after stimulation but a certain systemic amount of estrogen was necessary to make this effect evident. These results provide evidence that the hippocampus exerts an inhibitory influence on gonadotropin release. (Endocrinology85: 1154, 1969)