Cholecystokinin in the hypothalamo-hypophyseal system.

Immunohistochemical studies on cholecystokinin-like (CCK-ir) substances in colchicine-pretreated rats demonstrated that in addition to CCK-ir cells in the magnocellular portion of the paraventricular nucleus. CCK-ir cells are also present among the parvocellular neurons. Radioimmunoassay of CCK after paraventricular lesions indicate that most, if not all, of the CCK in the posterior pituitary and in the median eminence originates from the paraventricular nucleus. It appears that CCK-fibers, like other neuropeptidergic fibers from the paraventricular nucleus (vasopressin, oxytocin, TRH, CRF) enter the medial basal hypothalamus through a common gate--the lateral retrochiasmatic area--in traveling to the median eminence.