Planar lipid bilayers were formed from a solution of synthetic 1-palmitoyl-2-oleoyl-glycero-3-phosphoco line (POPC) and 1-palmitoyl-2-oleoyl-glycero-3-phosphoet hanolaminein (POPE, Avanti Polar Lipids, Birmingham, AL) in ratio 3:1 in n-decane (Aldrich). The solution was used to paint a bilayer in an aperture of ~150 μm diameter in a Delrin cup (Warner Instruments, Hamden, CT) between symmetric aqueous bathing solutions of 150 mM KCl, 20 mM Hepes, pH 7.2, at 22°C. All salts were ultrapure (>99%) (Aldrich). Bilayer capacitances were in the range of 50–75 pF. After the bilayers were formed, 0.2–0.5 μl of the TRPM8 micellar solution (2 μg/ml) was added to the cis compartment with gentle stirring. Unitary currents were recorded with an integrating patch clampamplifier (Axopatch 200A, Axon Instruments). The trans solution (voltage command side) was connected to the CV 201A head stage input, and the cis solution was held at virtual ground via a pair of matched Ag-AgCl electrodes. Currents through the voltage-clamped bilayers (background conductance <3 pS) were filtered at the amplifier output (low pass, −3 dB at 10 kHz, 8-pole Bessel response). Data were secondarily filtered at 50 Hz through an 8-pole Bessel filter (950 TAF,Frequency Devices) and digitized at 1 kHz using an analog-to-digital converter (Digidata 1322A, Axon Instruments), controlled by pClamp9 software (Axon Instruments). Single-channel conductance events, all points’ histograms, open probabilities and other parameters were identified and analyzed using the Clampfit9software (Axon Instruments).
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