Figure 4.

PKC activation by PMA downregulates the responses to cold and menthol in cold-sensitive neurons. (A) Ratiometric [Ca²⁺]_i response of representative cold thermoreceptor/menthol-sensitive neuron, from mouse TG. The protocol used consisted of a double application of a cold pulse followed by application of 100 µM menthol at 34 °C in cells perfused with control solution (open circles), 1 µM PMA (blue circles) or 1 µM 4α-PMA (grey circles). (B,C) Bar graph representing mean and S.E. and data points of ratio responses to cold (ΔC2/ΔC1) (B) and menthol (ΔM2/ΔM1) (C) for each condition. (D) Summary of the effect of different treatments on the temperature threshold of cold-evoked responses (T2-T1). Negative values indicate shifts towards lower temperatures (control, n = 10; PMA, n = 11 and 4α-PMA, n = 9). Statistical significance was assessed using a one-way ANOVA test in combination with a Dunnett’s post hoc test; *** p < 0.001, ** p < 0.01 and * p < 0.05, n.s. (not significant) p > 0.05 compared to control conditions.