TRPV1-lineage neurons are required for thermal sensation

The ion-channel TRPV1 is believed to be a major sensor of noxious heat, but surprisingly animals lacking TRPV1 still display marked responses to elevated temperature. In this study, we explored the role of TRPV1-expressing neurons in somatosensation by generating mice wherein this lineage of cells was selectively labelled or ablated. Our data show that TRPV1 is an embryonic marker of many nociceptors including all TRPV1- and TRPM8-neurons as well as many Mrg-expressing neurons. Mutant mice lacking these cells are completely insensitive to hot or cold but in marked contrast retain normal touch and mechanical pain sensation. These animals also exhibit defective body temperature control and lose both itch and pain reactions to potent chemical mediators. Together with previous cell ablation studies, our results define and delimit the roles of TRPV1- and TRPM8-neurons in thermosensation, thermoregulation and nociception, thus significantly extending the concept of labelled lines in somatosensory coding.