Choline acetyltransferase-like immunoreactivity in small diameter neurones of the rat dorsal root ganglion.

In the rat choline acetyltransferase (ChAT)-like immunoreactivity (ChAT-LI) was demonstrated in the dorsal root ganglion (DRG), in the superficial spinal cord and in the subepithelial layer of the ureter using immunohistochemical techniques. In the L1 DRG, 66% of the neurones were ChAT-LI. They did not express neurofilament immunoreactivity (RT97 negative) but could also contain calcitonin gene-related peptide-like immunoreactivity (CGRP-LI). In the superficial spinal cord and in the subepithelial plexus of the ureter--both areas where high numbers of fine afferent fibres have been demonstrated--CGRP-LI and ChAT-LI were co-distributed, indicating that ChAT can be found in the peripheral and central endings of small afferents. The data provide morphological evidence that a substantial proportion of afferent fibres are cholinergic.