Figure 7.

Mrgprd neurons contribute to the detection of painful heat. a, Representative in situ hybridization of sections through DRG from TRPV1-DTR/Mrgprd-DTR mice illustrates selective loss of TRPV1- and Mrgprd-expressing cells. b, A standard hot plate test that measures latency to show escape reactions to 55°C was used to examine responses to noxious heat; significant differences between genotypes were assessed using Student's t test. Mrgprd-DTR mice (pale gray bar) display withdrawal responses indistinguishable from controls (open bar), whereas TRPV1-DTR mice (red bars) exhibit reduced response to noxious heat (*p < 0.05). Additional ablation of TRPM8 cells (hatched bar) had no significant effect on response latency. In contrast, double mutants in which both the TRPV1 and Mrgprd cells were eliminated (dark gray bar) and TRPV1-DTA mice that extensively lack both of these classes of nociceptor (black bar) were essentially unresponsive within the cutoff for this assay. Data represent means ± SEM (n ≥ 6 animals).