Heck G L, Persaud K C, DeSimone J A
Department of Physiology, Virginia Commonwealth University, Richmond 23298-0551.
Biophys J. 1989 May;55(5):843-57. doi: 10.1016/S0006-3495(89)82884-X.
We have measured the NaCl or KCl currents under voltage clamp across the dorsal lingual epithelium of the rat and simultaneously the response of the taste nerves. Under short-circuit conditions a NaCl stimulus evoked an inward current (first current) that coincided with excitation of the chorda tympani. This was followed by a slower inward current (second current) that matched the kinetics of taste nerve adaptation. The peak first current and the coincident neural response satisfied the same saturating NaCl concentration dependence. Both first and second currents were partially blocked by amiloride as were the phasic and tonic components of the neural response. The NaCl-evoked second current was completely blocked by ouabain. Investigation of the NaCl-evoked current and the neural response over a range of clamped voltages showed that inward negative potentials enhanced the inward current and the neural response to 0.3 M NaCl. Sufficiently high inward positive potentials reversed the current, and made the neural response independent of further changes in voltage. Therefore, one of the NaCl taste transduction mechanisms is voltage dependent while the other is voltage independent. A KCl stimulus also evoked an inward short-circuit current, but this and the neural response were not amiloride-sensitive. The data indicate that neural adaptation to a NaCl stimulus, but not a KCl stimulus, is mediated by cell Na/K pumps. A model is proposed in which the connection between the NaCl-evoked second current and cell repolarization is demonstrated.
我们在电压钳制条件下测量了大鼠舌背上皮跨上皮的氯化钠或氯化钾电流，并同时记录了味觉神经的反应。在短路条件下，氯化钠刺激引发了一种内向电流（第一电流），这与鼓索神经的兴奋同时发生。随后是一种较慢的内向电流（第二电流），其动力学与味觉神经适应相匹配。第一电流的峰值和与之同时出现的神经反应满足相同的饱和氯化钠浓度依赖性。第一电流和第二电流都被氨氯吡咪部分阻断，神经反应的相位和紧张性成分也是如此。氯化钠诱发的第二电流被哇巴因完全阻断。在一系列钳制电压下对氯化钠诱发的电流和神经反应进行研究表明，内向负电位增强了内向电流以及对0.3M氯化钠的神经反应。足够高的内向正电位使电流反转，并使神经反应与电压的进一步变化无关。因此，氯化钠味觉转导机制之一是电压依赖性的，而另一个是电压非依赖性的。氯化钾刺激也引发了内向短路电流，但这一电流和神经反应对氨氯吡咪不敏感。数据表明，神经对氯化钠刺激而非氯化钾刺激的适应是由细胞钠/钾泵介导的。本文提出了一个模型，其中展示了氯化钠诱发的第二电流与细胞复极化之间的联系。
