[A study of transpial migration of implanted serotonergic neurons in rat spinal cord]

Transpial migration of implanted 5-HT neurons from the subarachnoid space into the spinal cord was studied in adult Wistar rats. Embryonic raphe tissue or cell suspension containing 5-HT cells was used as grafts. The implanted 5-HT cells were monitored by 5-HT immunohistochemical method. The results are as follows: (1) 10 d after cutting the spinal cord at lower thoracic level, 5-HT fibers disappeared in the transected spinal cord. (2) Raphe tissue was implanted into the subarachnoid space of the thoracic lumbar segment after the spinal cord was cut. One month later, 5-HT positive cells could be found in the transected spinal cord with fibers extending into both the grey and the white matters. (3) If the raphe cell suspension instead was implanted, a number of 5-HT positive cells appeared in the grey matter near the implanted region and the distribution of these cells in the grey matter was quite consistent with the implanted range of the cell suspension in the subarachnoid space. The 5-HT positive cells which had entered into the spinal cord sent out fibers and reestablished a new fiber network in the grey matter. (4) After implantation, the number of the 5-HT positive fibers in the transected grey matter became more and more sparsely distributed with increasing distance from the cell bodies and the 5-HT positive fibers reappeared in the white matter were much less than that in the grey matter. Present results show that the implanted 5-HT neurons are able to migrate transpially from the subarachnoid space into the spinal cord.