Endogenous cold responses in Xenopus oocytes. (A and B) Cold-sensitive currents recorded in control oocytes (A, uninjected; B, injected with water). (C) Endogenous cold-sensitive current was insensitive to RR block. Both wash and cooling buffers contained 20 µM RR. (D) Cold-response profiles of endogenous cold activity, showing similarly variable temperature activation thresholds as observed in frog TRPV3–expressing oocytes. All currents were recorded at a holding potential of −60 mV.