LOCALIZATION OF OXYTOCIN-BINDING SITES IN THE THORACIC AND UPPER LUMBAR SPINAL-CORD OF THE ADULT AND POSTNATAL RAT - A HISTOAUTORADIOGRAPHIC STUDY

Oxytocin binding sites were detected by autoradiography on films and e mulsion-coated sections in the spinal cord of adult and postnatal rats tram C8 to L2, using a highly selective I-125-labelled oxytocin antag onist. Oxytocin binding sites were detected on all transverse sections in the dorsal horn, where labelling was scattered over laminae I and II. The autonomic areas, i.e. the intermediolateral cell column, the c entral grey (lamina X) and the nucleus intercalatus were labelled. Bin ding in the intermediolateral cell column was most frequently observed on sections from T9 to T11 in adult and T7 to T8 in postnatal rats. i n this location, oxytocin binding sites were highly concentrated on ce ll bodies of putative sympathetic preganglionic neurons; however, not all of these cells were labelled. Diffuse labelling occurred on the do rsal part of the central grey, mainly between T8 and L2. isolated labe lled cells belonging to the nucleus intercalatus were scattered betwee n the central canal and the intermediolateral cell column. In addition , oxytocin binding sites were found on some motoneurons of the lateral group of T12-T13, but only in postnatal rats. The distribution of oxy tocin binding sites in the rat spinal cord coincides with that of the oxytocin innervation and strongly suggests a modulatory role of this p eptide in sensory and autonomic functions.