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.