Stereotaxic investigation of the lateral horn of the cat spinal cord

Coordinates of the lateral horn in segments C8-L3 were measured in specimens of the cat spinal cord, using the point of entry of the dorsal root as reference point. When choosing coordinates, various methods of orientation of the microelectrode used to test sympathetic preganglionic neurons (SPGNs) were considered. Electrophysiological investigation of SPGNs showed that the coordinates described here ensured correct placing of the microelectrode in the lateral horn. Determination of recording points suggests a compact arrangement of SPGNs in the dorsal part of the lateral horn. Slower conduction of antidromic excitation along the intramedullary part of the SPGN axons than along the peripheral part, detected by electrophysiological experiments, suggests that the axon of these neurons has a long, thin, nonmyelinated part.