Sequential opening of IP3-sensitive Ca2+channels and SOC during α-adrenergic activation of rabbit vena cava

α1-Aderenoceptor-mediated constriction of rabbit inferior vena cava (IVC) is signaled by asynchronous wavelike Ca2+ oscillations in the in situ smooth muscle. We have shown previously that a putative nonselective cationic channel (NSCC) is required for these oscillations. In this report, we show that the application of 2-aminoethoxyphenyl borate (2-APB) to antagonize inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ release channels (IP3R channels) can prevent the initiation and abolish ongoing α1-aderenoceptor-mediated tonic constriction of the venous smooth muscle by inhibiting the generation of these intracellular Ca2+ concentration ([Ca2+]i) oscillations. The observed effects of 2-APB can only be attributed to its selective inhibition on the IP3R channels, not to its slight inhibition of the L-type voltage-gated Ca2+ channel and the sarco(endo)plasmic reticulum Ca2+ ATPase. Furthermore, 2-APB had no effect on the ryanodine-sensitive Ca2+ release channel and the store-operated channel (SOC) in the IV...