Abstract：
Stimulation of sympathetic nerves in the vas deferens yields biphasic contractions consisting of a rapid transient component resulting from activation of P2X1 receptors by ATP and a secondary sustained component mediated by activation of α1-adrenoceptors by noradrenaline. Noradrenaline can also potentiate the ATP-dependent contractions of the vas deferens, but the mechanisms underlying this effect are unclear. The purpose of the present study was to investigate the mechanisms underlying potentiation of transient contractions of the vas deferens induced by activation of α1-adrenoceptors. Contractions of the mouse vas deferens were induced by electric field stimulation (EFS). Delivery of brief (1s duration) pulses (4 Hz) yielded transient contractions that were inhibited tetrodotoxin (100 nM) and guanethidine (10 µM). α,β-meATP (10 µM), a P2X1R desensitising agent, reduced the amplitude of these responses by 65% and prazosin (100 nM), an α1-adrenoceptor antagonist, decreased mean contraction amplitude by 69%. Stimulation of α1-adrenoceptors with phenylephrine (3 µM) enhanced EFS and ATP-induced contractions and these effects were mimicked by the phorbol ester PDBu (1 µM), which activates PKC. The PKC inhibitor GF109203X (1 µM) prevented the stimulatory effects of PDBu on ATP-induced contractions of the vas deferens but only reduced the stimulatory effects of phenylephrine by 40%. PDBu increased the amplitude of ATP-induced currents recorded from freshly isolated vas deferens myocytes and HEK-293 cells expressing human P2X1Rs by 93%. This study indicates that: (1) potentiation of ATP-evoked contractions of the mouse vas deferens by α1-adrenoceptor activation were not fully blocked by the PKC inhibitor GF109203X and (2) that the stimulatory effect of PKC on ATP-induced contractions of the vas deferens is associated with enhanced P2X1R currents in vas deferens myocytes.
摘要：
输精管中交感神经的刺激会产生双相收缩，该双相收缩由ATP激活P2X1受体引起的快速瞬时成分和去甲肾上腺素激活α1-肾上腺素受体介导的次要持续成分组成。去甲肾上腺素还可以增强输精管的ATP依赖性收缩，但这种效应的潜在机制尚不清楚.本研究的目的是研究α1-肾上腺素受体激活引起的输精管短暂性收缩的潜在机制。通过电场刺激(EFS)诱导小鼠输精管收缩。短暂（1s持续时间）脉冲（4Hz）的传递产生了抑制河豚毒素（100nM）和胍乙啶（10µM）的瞬时收缩。α,β-meATP（10µM），P2X1R脱敏剂，将这些反应的幅度降低了65%和哌唑嗪(100nM)，α1-肾上腺素受体拮抗剂,平均收缩幅度降低69%。用去氧肾上腺素（3µM）刺激α1-肾上腺素受体可增强EFS和ATP诱导的收缩，这些作用被佛波醇酯PDBu（1µM）模仿，激活PKC。PKC抑制剂GF109203X（1µM）阻止了PDBu对ATP诱导的输精管收缩的刺激作用，但仅将苯肾上腺素的刺激作用降低了40％。PDBu使从新鲜分离的输精管肌细胞和表达人P2X1R的HEK-293细胞记录的ATP诱导电流的幅度增加了93％。这项研究表明：（1）PKC抑制剂GF109203X并未完全阻断α1-肾上腺素受体激活对小鼠输精管ATP诱发的收缩的增强作用；（2）PKC对ATP诱导的输精管收缩的刺激作用与输精管肌细胞中P2X1R的电流增强有关。
