Development of peptide- and tyrosine hydroxylase-containing neurons in the fetal spinal cord transplanted into the anterior chamber of the eye of adult rats.

Fetal rat spinal cord transplanted into the anterior chamber of the eye of an adult rat was immunohistochemically stained using antisera to substance P (SP), neuropeptide Y (NPY), methionine-enkephalin (ENK), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and tyrosine hydroxylase (TH), and distributional changes of peptide- and enzyme-containing neurons 1, 2 and 4 weeks after transplantation were investigated. To examine the effect of colchicine on immunoreactivity, unilateral eyes of these adult host rats received intraocular colchicine treatment. Without colchicine treatment, numerous SP- and CGRP-immunoreactive (IR) neurons were observed in the graft 1 week after transplantation, and their immunoreactivity gradually decreased up to 4 weeks after transplantation. NPY-, ENK-and VIP-IR neurons first appeared in the graft 2 weeks after transplantation. Four weeks after transplantation, the immunoreactivity of NPY and ENK decreased significantly, whereas VIP-IR neurons showed the same intensity as that observed at 2 weeks after transplantation. TH-IR neurons, on the other hand, were seen at every stage, but their immunoreactivity was constant all the time. After colchicine treatment, the number of SP-, NPY-, ENK- and CGRP-IR neurons appeared to increase, while that of VIP- and TH-IR neurons did not change significantly. The distribution patterns of the peptide- and enzyme-containing fibers differed from each other. In the analysis of serial sections stained with 5 peptides (SP, NPY, ENK, VIP, CGRP), fibers containing these peptides were found to be densely accumulated in specific areas of the transplanted spinal cord. The present findings demonstrated that most of the peptide- and enzyme-containing neuron systems in the transplanted spinal cord showed similar distribution patterns and development to those in the normal spinal cord, but that some displayed different distribution.