DISTRIBUTION OF ANGIOTENSIN-II RECEPTOR-BINDING IN THE SPINAL-CORD OF THE SHEEP

The distribution of angiotensin II binding sites has been mapped at segmental levels throughout the spinal cord of the sheep using in vitro autoradiographic methods. Binding of I-125-[Sar(1), Ile(8)] Ang II is most prominent in the lateral horns of the thoracolumbar and sacral regions containing the sympathetic and parasympathetic preganglionic neurons respectively. Binding is also present in the dorsal horns of the grey matter, in the central canal region, dorsal root ganglia and associated with non-neuronal elements such as the ependyma surrounding the central canal, and blood vessels. Displacement with receptor antagonists specific for AT(1) and AT(2) subtypes, indicates that angiotensin II receptors in the spinal cord are of the AT(1) type. These data help to interpret the physiological actions of angiotensin II in the spinal cord, particularly with respect to its autonomic components.