, 2009), we found that PS at 10 μM shifted the thermal response profile of TRPM3-expressing cells to lower temperatures by 6.1 ± 0.4 degrees (Figure 6A). Conversely, we found that increasing the temperature from room temperature to 37°C strongly potentiated PS responses (Figures 6B and 6C). Interestingly, PS concentrations as low as 100 nM, which are subthreshold at room temperature, evoked robust responses at 37°C (Figures 6B and 6C). The synergism between heat and PS was

further confirmed in whole-cell current measurements, where the current response to a low dose Selleckchem MLN8237 of PS (5 μM) was strongly potentiated at higher temperatures (Figures 6D–6F). Taken together, these data demonstrate that heterologously expressed TRPM3 functions as a heat-activated channel, capable of integrating chemical and thermal stimuli. To analyze the possible contribution of TRPM3 to heat sensitivity in DRG and TG neurons, we used Ca2+ imaging to probe for heat responses in sensory neurons from Trpm3+/+ and Trpm3−/− mice and to correlate heat responsiveness with sensitivity to PS and capsaicin ( Figure 7A). In line with earlier work ( Fischbach et al., 2007 and Woodbury et al., 2004),

we found that the large majority of sensory neurons from Trpm3+/+ mice showed heat sensitivity, with 82% of DRG neurons (111/135) and 79% of TG Selleck IBET151 neurons (126/159) responding to a 43°C heat stimulus. The heat-sensitive population could be further classified in four groups based on PS and capsaicin sensitivity. The largest fraction of heat-positive Trpm3+/+ DRG neurons (59/135; 43%) responded to both PS and capsaicin. In addition, 33% of the heat-sensitive neurons responded to PS but not to capsaicin (45/135), and 3% responded to capsaicin but not to PS (4/135). Finally,

3 out of 135 (2%) were insensitive unless to both capsaicin and PS ( Figure 7C). The responsiveness to heat was not different when the thermal stimulus was applied prior to the chemical agonists (data not shown). A similar response profile was obtained in Trpm3+/+ TG neurons and in TRPV1+/+ DRG and TG neurons ( Figure 7D). Sensory neurons from Trpm3−/− mice showed a moderate but significant reduction in the heat sensitivity, with 59% of DRG neurons (129/217; p < 0.001) and 63% of TG neurons (150/236; p < 0.001) responding to a 43°C heat stimulus ( Figures 7B–7D). In particular, the subgroup of heat-sensitive neurons responding to PS but not to capsaicin was strongly reduced in the Trpm3−/− mice ( Figures 7B–7D). For comparison, we also analyzed heat, PS, and capsaicin sensitivity in neurons isolated from Trpv1−/− mice. Here, we found that 60% of DRG neurons and 62% of TG neurons responded to heat ( Figures 7C and 7D). The large majority of heat-sensitive Trpv1−/− neurons also responded to PS (10 μM) application ( Figures 7C and 7D).