Capsaicin sensitivity is associated with the expression of the vanilloid (capsaicin) receptor (VR1) mRNA in adult rat sensory ganglia.

A vanilloid receptor (VR1) has recently been cloned and shown to be a target for capsaicin, the excitotoxic component of capsicum peppers (Caterina, M.J., Schumacher, M.A., Tominaga, M., Rosen, T.A., Levine, J.D. and Julius, D., Nature, 389 (1997) 816-824). The effects of capsaicin appear to be selective for a subset of sensory neurones which includes polymodal nociceptors. The present study describes the distribution of VR1 mRNA, together with measurements of capsaicin sensitivity, in sensory nerve ganglia of different embryological origins and a single sympathetic ganglion, the superior cervical ganglion (SCG). In situ hybridisation revealed the expression of VR1 mRNA in small-to-medium-sized neurones of the dorsal root, trigeminal and vagal ganglia. No hybridisation signal was observed in the SCG neurones. This pattern of expression correlated with capsaicin sensitivity measured by whole-cell voltage clamp where, in similar sized cells, over 80% of neurones from dorsal root and vagal ganglia were capsaicin sensitive, but all SCG neurones were insensitive to capsaicin.