The distribution of thyrotropin-releasing hormone (TRH) in the rhesus monkey spinal cord

The distribution of thyrotropin-releasing hormone (TRH) in the Rhesus monkey spinal cord was studied using a highly specific antibody to TRH and the indirect peroxidase-antiperoxidase technique. TRH-positive fibers were found at all levels of the spinal cord and were in greatest concentration in the ventral gray, intermediolateral column and central gray. All motor nuclear groups in lamina IX of the ventral gray were innervated by TRH, frequently in close association with perikarya of alpha-motoneurons. The motor nuclei in the lumbar cord were the most heavily stained and contrasted to the minimal staining in the retrodorsolateral nuclear groups of the cervical, thoracic and sacral cord. Within the intermediolateral column, which contains the majority of preganglionic sympathetic neurons, TRH terminal fields reached their highest density between T2-T4 and T12-L2. Other preganglionic neurons including the nucleus intercalatus spinalis and the dorsal commissural nucleus were also densely innervated. These studies demonstrate the preferential distribution of TRH in the monkey spinal cord to regions containing alpha-motoneurons and preganglionic neurons and indicate that TRH may play an important role in the regulation of motor function and in the autonomic nervous system.