Figure 3

Potentiation of TRPV1 currents by ET-1 in HEK293 cells cotransfected with TRPV1 and the ET _A R. A – C, Potentiation of capsaicin-activated currents by ET-1. A, Recording of current at -60 mV showing the potentiation of responses to capsaicin (10 nM) by the application of ET-1 (100 nM). B, IV-relationships recorded at the times indicated by the numbers 1 – 4 in A. C, Bar graph summarizing the potentiation of TRPV1 responses to capsaicin by ET_AR activation in HEK293 cells. The bars show the normalized control response prior to ET-1 application and the normalized first (n = 10, p = 0.0009) and second (n = 9, p = 0.0012) responses after ET-1 application. D – F, Potentiation of H⁺-activated currents by ET-1. D, ET-1 increased the amplitude of TRPV1 responses to pH 5.1. Currents were recorded at -60 mV and applications of pH 5.1 preceded by a solution of pH 6.8 to prevent the activation of endogenous ASICs. E, IV-relationships recorded at the times indicated by numbers in D. F, Bar graph summarizing the potentiation of the TRPV1 response to pH 5.1 by ET-1, and showing the normalized response before ET-1, and the first (n = 12, p < 0.0001) and second (n = 9, p = 0.0069) responses after ET-1. G – J, Potentiation of heat-activated currents through TRPV1 by ET-1. G, Current recordings at -60 mV (upper traces) showing consecutive responses of a control cell to heating to 44°C (left), and responses from a cell treated with ET-1 after the first response to heat (right). The lower traces show the temperature recorded in the chamber close to the cell. H, I-V relationships recorded at the times indicated by the numbers in G. I, Bar graph summarizing the potentiation of the normalized first (n = 10, p = 0.0252) and second (n = 7, p = 0.0233) responses to heat after ET-1. J, Plot of the current-temperature relationships for the control response (filled squares) and the second response after ET-1 (open squares) from the experiment in G.