Gao Zhaohui, Kehoe Valerie, Sinoway Lawrence I, Li Jianhua
Division of Cardiology, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Am J Physiol Heart Circ Physiol. 2005 May;288(5):H2238-43. doi: 10.1152/ajpheart.01095.2004. Epub 2004 Dec 22.
Static contraction of skeletal muscle evokes increases in blood pressure and heart rate. Previous studies suggested that the dorsal horn of the spinal cord is the first synaptic site responsible for those cardiovascular responses. In this study, we examined the role of ATP-sensitive P2X receptors in the cardiovascular responses to contraction by microdialyzing the P2X receptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) into the L7 level of the dorsal horn of nine anesthetized cats. Contraction was elicited by electrical stimulation of the L7 and S1 ventral roots. Blockade of P2X receptor attenuated the contraction induced-pressor response [change in mean arterial pressure (delta MAP): 16 +/- 4 mmHg after 10 mM PPADS vs. 42 +/- 8 mmHg in control; P < 0.05]. In addition, the pressor response to muscle stretch was also blunted by PPADS (delta MAP: 27 +/- 5 mmHg after PPADS vs. 49 +/- 8 mmHg in control; P < 0.05). Finally, activation of P2X receptor by microdialyzing 0.5 mM alpha,beta-methylene into the dorsal horn significantly augmented the pressor response to contraction. This effect was antagonized by prior PPADS dialysis. These data demonstrate that blockade of P2X receptors in the dorsal horn attenuates the pressor response to activation of muscle afferents and that stimulation of P2X receptors enhances the reflex response, indicating that P2X receptors play a role in mediating the muscle pressor reflex at the first synaptic site of this reflex.
骨骼肌的静态收缩会引起血压和心率升高。先前的研究表明，脊髓背角是负责这些心血管反应的首个突触位点。在本研究中，我们通过将P2X受体拮抗剂磷酸吡哆醛 - 6 - 偶氮苯基 - 2',4'-二磺酸（PPADS）微量透析至9只麻醉猫的脊髓背角L7水平，研究了ATP敏感性P2X受体在心血管对收缩反应中的作用。通过电刺激L7和S1腹根引发收缩。P2X受体的阻断减弱了收缩诱导的升压反应[平均动脉压变化（ΔMAP）：10 mM PPADS后为16±4 mmHg，而对照组为42±8 mmHg；P < 0.05]。此外，PPADS也使对肌肉拉伸的升压反应减弱（ΔMAP：PPADS后为27±5 mmHg，而对照组为49±8 mmHg；P < 0.05）。最后，通过向背角微量透析0.5 mM α,β - 亚甲基激活P2X受体，显著增强了对收缩的升压反应。这种效应被预先的PPADS透析所拮抗。这些数据表明，脊髓背角中P2X受体的阻断减弱了对肌肉传入神经激活的升压反应，而P2X受体的刺激增强了反射反应，表明P2X受体在该反射的首个突触位点介导肌肉升压反射中发挥作用。
