HYPOPHYSIOTROPHIC AREA IN THE HYPOTHALAMUS

Abstract

SUMMARY Anterior pituitary tissue was implanted into the hypothalamus, other parts of the brain and beneath the renal capsule of rats. Grafts in the ventral hypothalamus could retain a normal histological appearance despite a lack of any contact with the capillary loop system of the median eminence. By observing the location of basophils in the grafts a 'hypophysiotrophic' area has been defined. In other sites the histological structure of the grafts was not maintained. In animals with grafts in the hypophysiotrophic area the target organs might be well preserved, though sometimes the gonads were preserved and other target organs atrophied. Grafts in other sites always led to atrophy of the target organs. It is concluded that the material from the hypothalamus essential for the maintenance of anterior pituitary structure and function is not simply a synaptic mediator discharged by nerve terminals into the portal circulation, but a true neurosecretory substance produced by and available from small neurones in the hypothalamus.