Figure 3.

TRPM8 is primarily activated by testosterone. TRPM8 channel activity was assessed in planar lipid bilayers in the presence of varying concentrations of steroid hormones: testosterone (or membrane impermeable BSA‐testosterone), dihydrotestosterone (DHT), progesterone, and estradiol. All stock solutions of the membrane‐permeable steroids were prepared in ethanol, which upon application were diluted 1/1000, reaching a final concentration of ethanol 0.1%. BSA‐testosterone stock solution was prepared in the phosphate buffer, pH 7.5. A, representative single channel currents at 100 mV of TRPM8 activated in the presence of indicated steroids and 2.5 μM DiC₈ PIP₂. Note BSA‐testosterone‐, progesterone‐, and estradiol‐induced TRPM8 openings only into the small conductance state. B, current‐voltage (I‐V) relationship for TRPM8 currents induced by testosterone (T), 17β‐estradiol (E), progesterone (P), and BSA‐testosterone (BSA‐T). C, concentration response curves of TRPM8 activation by testosterone, DHT, progesterone, and estradiol obtained in the presence of 2.5 μM DiC₈ PIP₂ at 60 mV, number of events (channel gating) analyzed for progesterone = 247,520 and for estradiol = 281,483. Data points represent mean ± s.e.m. of n = 51 experiments and were fitted by linear regression (B) or Hill equation (C), which yielded single channel conductance and EC₅₀ values, respectively, as shown