Figure 1

Responses of wild-type, p35KO, Cdk5CoKo, TRPV1KO and Tgp35 mice to capsaicin and heat.

Water-deprived C57Bl6 and FVBN mice were tested for 1 h using the lickometer with a free access to water containing 15 μM capsaicin. The behavior is expressed as a % of the baseline licking responses for plain water as compared to capsaicin. Increased aversion and hypersensitivity to capsaicin was evident in Tgp35 mice (FVBN background) by decreased number of licks (unpaired t-test, p < 0.05). In contrast, p35 knockout or Cdk5CoKo mice (C57BL6/129SVJ background) showed less aversion to capsaicin compared to their littermate wild-type (WT) controls (One-way ANOVA followed by Dunnett’s multiple comparisons test, p < 0.0001). Data are presented as mean ± SEM from four animals during five different measurements (a). Effect of temperature activation of TRPV1 in mutant animals. An orofacial pain assessment device was used to measure the responses of the mice to hot facial stimulation. All mice showed similar consumption of the reward (sucrose) at 37 °C (b). Tgp35 mice displayed an aversive behavior to the increased temperature of the thermodes as noted by significantly decreased licking behavior (unpaired t-test, p = 0.0002), whereas p35KO mice displayed significantly increased number of licks compared to wild-type controls (One-way ANOVA followed by Dunnett’s multiple comparisons test, p < 0.05) (c). Data are presented as mean ± SEM from four animals measured five times using 37 °C and three times at 45 °C.