A, α,β-meATP (10 μm, filled circles) had no effect in PDGFRα+ cells at holding potential of −60 mV. B, α,β-meATP (1 μm, filled circles) transiently activated inward current in smooth muscle cells (SMC) held at −60 mV. Responses to 2nd application of α,β-meATP were minimal due to significant desensitization. C, ATP (100 μm, filled circles) also activated transient inward currents in SMCs held at −60 mV. Responses to 2nd application of ATP were minimal due to significant desensitization. Filled arrowheads denote ramp depolarizations. Dotted lines denote 0 pA. Filled circles denote drug applications by Picospritzer (10 p.s.i., 1 s).