Rodgers Corinne I, Labrie John D, Robertson R Meldrum
Department of Biology, Queen's University, Biosciences Complex, Kingston, Ontario K7L 3N6, Canada.
J Insect Physiol. 2009 Jul;55(7):599-607. doi: 10.1016/j.jinsphys.2009.03.004. Epub 2009 Mar 26.
Stress-induced arrest of ventilatory motor pattern generation is tightly correlated with an abrupt increase in extracellular potassium concentration ([K+]o) within the metathoracic neuropil of the locust, Locusta migratoria. Na+/K+-ATPase inhibition with ouabain elicits repetitive surges of [K+]o that coincide with arrest and recovery of motor activity. Here we show that ouabain induces repetitive [K+]o events in a concentration-dependent manner. 10(-5)M, 10(-4)M, and 10(-3)M ouabain was bath-applied in semi-intact locust preparations. 10(-4)M and 10(-3)M ouabain reliably induced repetitive [K+]o events whereas 10(-5)M ouabain had no significant effect. In comparison to 10(-4)M ouabain, 10(-3)M ouabain increased the number and hastened the time to onset of repetitive [K+]o waves, prolonged [K+]o event duration, increased resting [K+]o, and diminished the absolute value of [K+]o waves. Recovery of motor patterning following [K+]o events was less likely in 10(-3)M ouabain. In addition, we show that K+ channel inhibition using TEA suppressed the onset and decreased the amplitude of ouabain-induced repetitive [K+]o waves. Our results demonstrate that ventilatory circuit function in the locust CNS is dependent on the balance between mechanisms of [K+] accumulation and [K+] clearance. We suggest that with an imbalance in favour of accumulation the system tends towards a bistable state with transitions mediated by positive feedback involving voltage-dependent K+ channels.
应激诱导的呼吸运动模式生成停滞与飞蝗（Locusta migratoria）后胸神经纤维网中细胞外钾离子浓度（[K+]o）的突然升高密切相关。用哇巴因抑制钠钾ATP酶会引发[K+]o的重复激增，这与运动活动的停滞和恢复相吻合。在此我们表明，哇巴因以浓度依赖的方式诱导[K+]o的重复事件。在半完整的飞蝗标本中，将10(-5)M、10(-4)M和10(-3)M的哇巴因进行浴式给药。10(-4)M和10(-3)M的哇巴因可靠地诱导了[K+]o的重复事件，而10(-5)M的哇巴因没有显著影响。与10(-4)M的哇巴因相比，10(-3)M的哇巴因增加了[K+]o重复波的数量并加快了其起始时间，延长了[K+]o事件的持续时间，提高了静息[K+]o，并减小了[K+]o波的绝对值。在10(-3)M的哇巴因作用下，[K+]o事件后运动模式恢复的可能性较小。此外，我们表明使用四乙铵抑制钾通道可抑制哇巴因诱导的[K+]o重复波的起始并降低其幅度。我们的结果表明，飞蝗中枢神经系统中的呼吸回路功能取决于[K+]积累和[K+]清除机制之间的平衡。我们认为，当积累机制占优势导致失衡时，系统倾向于进入双稳态，其转变由涉及电压依赖性钾通道的正反馈介导。
