Smooth Muscle Research Centre, Dundalk Institute of Technology, Dublin Road, Dundalk, Co. Louth, Ireland.
Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, 95616, USA.
Purinergic Signal. 2024 Oct;20(5):547-557. doi: 10.1007/s11302-024-09993-y. Epub 2024 Feb 20.
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 α-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 α-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 α-adrenoceptor antagonist, decreased mean contraction amplitude by 69%. Stimulation of α-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 α-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.
刺激输精管中的交感神经会产生双相收缩，包括由 ATP 激活 P2X1 受体引起的快速瞬态成分和由去甲肾上腺素激活α-肾上腺素受体引起的继发性持续成分。去甲肾上腺素也可以增强输精管对 ATP 的依赖性收缩，但这种效应的机制尚不清楚。本研究的目的是探讨激活α-肾上腺素受体增强输精管瞬态收缩的机制。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（4 Hz）的传递产生了被四氢生物蝶呤（100 nM）和胍乙啶（10 µM）抑制的瞬态收缩。α，β-meATP（10 µM），一种 P2X1R 脱敏剂，使这些反应的幅度降低了 65%，而普萘洛尔（100 nM），一种α-肾上腺素受体拮抗剂，使平均收缩幅度降低了 69%。用苯肾上腺素（3 µM）刺激α-肾上腺素受体增强了 EFS 和 ATP 诱导的收缩，这种作用被佛波酯 PDBu（1 µM）模拟，PDBu 激活 PKC。PKC 抑制剂 GF109203X（1 µM）阻止了 PDBu 对输精管中 ATP 诱导收缩的刺激作用，但仅将苯肾上腺素的刺激作用降低了 40%。PDBu 增加了从新鲜分离的输精管平滑肌细胞和表达人 P2X1R 的 HEK-293 细胞记录的 ATP 诱导电流的幅度，增加了 93%。本研究表明：（1）α-肾上腺素受体激活增强 ATP 诱导的小鼠输精管收缩作用并未被 PKC 抑制剂 GF109203X 完全阻断；（2）PKC 对输精管中 ATP 诱导收缩的刺激作用与输精管平滑肌细胞中 P2X1R 电流的增强有关。
