Fig. 2

PP121 inhibited high K⁺ or ACh-induced extracellular calcium influx. A Under 0 mM calcium conditions, 80 mM K⁺ failed to evoke the contraction of mTRs. When [Ca]²⁺ was restored to 2 mM, 80 mM K⁺-induced steady precontraction of mTRs, which could be completely relaxed by 56 µM PP121 (n = 6/6 mice). B In the presence of 56 µM PP121, 80 mM K⁺ failed to induce precontraction on mTRs during 0 to 2 mM Ca²⁺ restoration (n = 6/6 mice). C Under the 0 mM calcium condition, 100 µM ACh induced a transient and sharp contraction. When 2 mM [Ca]²⁺ was restored, 100 µM ACh induced a steady contraction, which could be eliminated by 40 µM PP121 (n = 6/6 mice). D In the presence of 40 µM PP121, 100 μM ACh failed to induce precontraction on mTRs during 0 to 2 mM Ca²⁺ restoration (n = 6/6 mice)