INDUCTION OF BEHAVIORAL AND ELECTROENCEPHALOGRAPHIC CHANGES IN THE RABBIT BY HORMONE ADMINISTRATION OR BRAIN STIMULATION1

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Abstract
The EEG after-reaction which ordinarily follows coitus in the female rabbit can be induced by "inhibitory-type" low frequency (5/sec), low voltage (0.01-1.0V) electrical stimulation, applied through chronically implanted electrodes to the hypothalamus, the olfactory bulb, the septum, the hippocampus or the amygdala. Following electrical stimulation at these voltages (too low to induce ovulation), the phase of sleep spindles may start immediately, and the latency of the stage of hippocampal hyperactivity is much shorter than that following coitus. The EEG after-reaction occurs "spontaneously" after treatment with placental gonadotropins, HCG and PMS, pituitary gonadotropins, LH and LTH, and neurohypophy-sial hormones, but the latency is greater than that following electrical stimulation. Inasmuch as the effective pituitary hormones are those whose release mechanisms are activated by coital stimuli, the results, are consistent with the hypothesis that the induction of the post-coital after-reaction may be mediated by pituitary hormones acting back on the nervous system. Such a neuroendocrine negative feed-back mechan-ism might serve to inhibit the release of superfluous ovulating hormone.