Figure 2.

Extracellular ATP or UTP potentiates capsaicin-evoked currents in DRG neurons from wild-type or P2Y₁-deficient mice. A–C, Representative traces of increases in the capsaicin (CAP)-activated currents by extracellular ATP (100 μm) in DRG neurons from wild-type (WT) (B) or P2Y₁-deficient (C) mice. A shows a control trace without ATP pretreatment. Holding potential was -60 mV. D, A representative trace of increases in the capsaicin-activated currents by UTP (100 μm) in DRG neurons from wild-type mice. E, Effects of ATP, UTP, or UTP plus suramin (50 μm) on the capsaicin-activated currents. Currents were normalized to the currents initially evoked by capsaicin (100 nm) in the absence of the additives. Normalized currents in the absence of ATP in wild-type mice, in the presence of ATP in wild-type mice, in the presence of ATP in P2Y₁-deficient mice, in the presence of UTP in wild-type mice, or in the presence of UTP plus suramin in wild-type mice were 1.07 ± 0.26 (n = 3), 4.01 ± 0.92 (n = 8), 4.37 ± 0.74 (n = 4), 6.24±1.58 (n = 4), or 0.95 ± 0.57 (n = 3), respectively. ^*p < 0.05 and ^**p < 0.01 versus absence of ATP in wild type; ^#p < 0.05 versus presence of UTP and suramin in wild type; two-tailed unpaired t test. WT, Wild type.