Autoradiographic demonstration of alpha 2 adrenoceptors in the bovine neurohypophysis.

Autoradiography of sections from neurohypophyses treated with tritiated clonidine has shown specific binding to alpha 2-adrenoceptor sites in the neurohypophysis but not in the intermediate lobe. Other studies have shown that alpha 2 agonists such as clonidine can cause a fall in circulating antidiuretic hormone; it is therefore possible to speculate that this action could be a direct one on the neurohypophysis since the appropriate binding sites have been shown to exist.