Fig. 1

Direct effect of hypoxia on TRPV1 overexpressed in HEK293T cells. a I–V curves were obtained by applying repetitive ramp-like pulses (from −80 to 80 mV, 0.4 V/s, 10 s interval). The representative I–V curves at each condition (control, hypoxia, 2 μM capsaicin) were averaged for comparison (n = 18). The membrane conductance was slightly increased by hypoxia (3% \( {\text{P}}_{{{\text{O}}_{2} }} \)), and maximally increased by 2 μM capsaicin (left panel). The right panel shows a summary of normalized inward currents at −20 mV and their changes by 3% \( {\text{P}}_{{{\text{O}}_{2} }} \) (n = 18) and 9% \( {\text{P}}_{{{\text{O}}_{2} }} \) (n = 10), respectively. In each tested cell, the inward current was normalized to the maximum currents induced by 2 μM capsaicin. b Inhibition of the basal activity of TRPV1 by capsazepine. Also, the combined hypoxia had no effect on membrane conductance in the presence of capsazepine (0.5 or 5 μM). c No effect of hypoxia and capsaicin on I–V curves of GFP-only transfected cells (n = 10). Cap capsaicin, con control, CPZ capsazepine