Figure 2.

Capsaicin, protons, and heat activate VR1 receptors. (A) Inward currents induced by two consecutive applications of the maximally effective dose (10 μM) of capsaicin. Capsaicin was applied to VR1-injected oocytes for 15 s (solid bar), perfused for 5–10 min (axis break marks), and reapplied for a 15-s pulse (solid bar). (B) Inward currents induced by two consecutive applications of maximally effective (pH 4.5) buffers. Solutions set to pH 4.5 were perfused for 15 s or 25 s (solid bars). (C) Upper trace: Current response of VR1 receptors to changes in temperature. Lower trace: Perfusate temperatures. The vertical lines indicate the threshold temperatures for VR1 channel activation and channel deactivation. (D) Representative plots of normalized current responses in response to increases in perfusate temperature. Temperature ramps from ≅22°C to 48 and 49°C in 12 oocytes injected with VR1 mRNA. Inward current magnitudes are normalized to peak currents. V_h = −25 mV.