Vanilloid receptor homologue, VRL1, is expressed by both A- and C-fiber sensory neurons

The capsaicin receptor (VRI) homologue, VRLI, is thought to be responsible for transducing high-threshold heat responses in Ab-fiber neurons. In the present study, the expression of VRLI by A- or C-fiber sensory neurons in rats was investigated by using a VRLI and 200 kDa neurofilament (NF200, an A-fiber marker) double immunohistochemical staining method. Approximately 46% of VRL-positive neurons were NF200 positive. Though double-labeled neurons tended to be medium to large, many VRLI single-labeled neurons were large. Dense VRLI immunoreactivity was also found in laminae I and II of the spinal dorsal horn, where nociceptive A delta- and C-fibers normally terminate. These results suggest that both C-fiber and Ab-fiber primary sensory neurons express VRLI, and VRLI may play an important role in nociception. NeuroReport 12:3693-3695 (C) 2001 Lippincott Williams & Wilkins.