Cold-sensitive, menthol-insensitive neurons in the murine sympathetic nervous system.

Several mechanisms have been implicated in underlying the perception of cold, most notably the activation of TRPM8 and TRPA1. We have used ratiometric calcium imaging to reveal a population of neurons in the superior cervical ganglion (SCG) of the mouse that respond to cooling but are insensitive to menthol. Furthermore we show that the expression of the mRNA transcripts encoding the recently identified noxious cold-sensitive channel TRPA1 but not TRPM8 are expressed in the SCG. These data provide evidence for a population of cold-responsive neurons in the SCG whose cold-responsiveness could be mediated by the activation of TRPA1 and suggest that the sympathetic nervous system may play a direct role in mediating sympathetic responses to cold temperatures.