The hypothalamo-choridal tract. II. Ultrastructural response of the choroid plexus to vasopressin.

Light and electron microsopic examination of choroid plexuses from lateral ventricles of water-deprived and subcutaneously or intravenously vasopressin administered rats reveal morphologic changes typical for vasopressin responsive fluid transporting epithelia during hormonal stimulation. Ultrastructural changes noted in both dehydrated and vasopressin treated animals included: the frequent occurrence of choroidal "dark" cells, dilatation of the lateral and basal intercellular spaces, increased vacuolization of the apical cytoplasm, and a change in microvillar conformation from the normal clavate type to those with a filiforma shape. On the basis of the ultrastructural changes observed it is proposed that the choroids plexus be regarded as a target tissue for vasopressin. These findings indicated that a vasopressin mediated transchoroidal cerebrospinal fluid absorption capability exists.