ABSTRACT
The purpose of this study was taken after transplantation of fetal serotonin and substance-P containing raphe nuclei into the transected thoracic spinal cord (T9-10) of adult rats, a suspension of cells derived from the mesencephalic and medullary raphe nuclei of 13~15 days embryonic rats were injected upper and lower the transected spinal cord. After survival periods of 15 days to 1 year, the animals were sacrificed and the spinal cord, processed for the localization of serotonin and substance-P immunoreactive neurons in the transplanted spinal cord, was studied using ABC immunocytochemistry. Immunocytochemical analysis revealed the presence of many serotonin and substance-P immunoreactive neurons in the transplants. In the mesencephlic implants, however, the serotonin and substance-P immunoreactive neurons were not co-localized with the same neurons. The serotonin and substance-P nerve fibers were densely distributed in lamina I and II of the dorsal horn and in lamina VIII and IX of the ventral horn of all segments of the spinal cord. The nontransplanted control, spinal cord of the rats showed a total absence of serotonin and substance-P immunoreactive fibers below the section. Immunoelctronmicroscopic anlysis demonstrated the presence of numerous synaptic contacts formed by serotonin and substance-P containing boutons which are most likely emanated from the grafted serotonin and substance-P.