Effects of sheep pineal fractions on the activity of male rat hypothalami in vitro.

High molecular weight substances could be isolated from sheep pineals with the "Bensinger" extraction method, followed by ultrafiltration of the waterlayer through different diaflomembranes. Two of the pineal fractions, XM100R and PM30R, stimulate the gonadotropin releasing activity of the medial basal hypothalamus (MBH). In experiments in which comparable pineal fractions were incubated without MBH and without pituitary and injected in immature mice no effect was detectable. All experiments in which a similar amount of rat cerebral cortex was used for incubation with pineal fractions did not show any activity.