Luteinizing Hormone Releasing Activity in Different Parts of Rabbit and Dog Brain

Abstract

Activation of ovarian progestin secretion was used to evaluated the LH-releasing activity (LH-RF) of tissue extracts injected into the anterior pituitaries of pregnant or pseudo-pregnant rabbits. Progestin secretion from ovaries 4-5 days following ovulation give the most consistent results as a semiquantitative measure of LH-RH. Acid extracts of median eminence, posterior hypothalamus, mesencephalic reticular formation and central gray matter, anterior hypothalamus and amygdaloid complex prepared from rabbit or dog brain contained considerable LH-RF activity which was not detectable in thalamus, hippocampus, white matter or cerebral cortex preparations. Cholinergic and adrenergic substances, histamine, vasopressin and oxytocin failed to induce significant LH release on intrapituitary application; but vasopressin, oxytocin, cholinergic substances and histamine did increase LH secretion when applied intratuberally. The stimulating actions of these chemical agents as well as those of the posterior pituitary hormones were considered to be nonspecific and incidental to their ability to liberate LH-releasing principle(s) from neural tissue.