Intraspinal transplants of serotonergic neurons in the adult rat

Adult male Sprague-Dawley rats were made paraplegic by a complete transection of the spinal cord at lower thoracic level. One week later they were transplanted, below the level of the section, with a cell suspension prepared from the raphe region of 14-day embryos. After survival periods of 10 days to 1 year, the animals were sacrificed and the spinal cord processed for the immunocytochemical detection of 5-HT. Axons from grafted cells grew extensively into the grey matter of the host, and established axosomatic and axodendritic synapses in the anterior horn and intermediolateral column, similar to those of the intact animal. In addition, a group of transplanted animals was tested for sexual reflexes which are under the control of serotonin. It was found that ejaculation reflexes, which are absent in paraplegic rats, are restored in transplanted animals.