Neonate rat sympathetic preganglionic neurons intracellularly labelled with lucifer yellow in thin spinal cord slices.

Sympathetic preganglionic neurons and interneurons were intracellularly labelled with lucifer yellow in thin transverse spinal cord slices of neonatal rats. Preganglionic neurons had spindle or oval shape somata and were located in the intermediolateral nucleus. The axons of these neurons coursed ventrally along the border of gray matter and exited the ventral horn; two to four long dendrites projected medially to the central canal and several relatively short dendrites oriented toward the lateral white matter. Interneurons were generally multipolar and located outside the immediate area of intermediolateral nucleus; their axons could sometimes be traced to the ventral funiculus. Interestingly, dye-coupled preganglionic neurons were observed for the first time. Our findings suggest that the dendritic domain of neonatal rat sympathetic preganglionic neurons is out-reaching and may represent potential sites of interaction with incoming segmental and/or descending inputs. In addition, the observation of dye-coupled preganglionic neurons raises the possibility that these neurons may have the capability of recruiting and/or synchronizing sympathetic outflow.