Jiang Z G, Qiu J, Ren T, Nuttall A L
Oregon Hearing Research Center, NRC-04, Oregon Health Sciences University, Portland, OR 97201, USA.
Hear Res. 1999 Dec;138(1-2):171-80. doi: 10.1016/s0378-5955(99)00166-5.
Blood circulation changes in the inner ear play an important role in many physiological and pathological conditions of hearing function. The spiral modiolar artery (SMA) is the terminal artery to the cochlea. It was surrounded with nerve fibers immunostained by an antibody for tyrosine hydroxylase. By using intracellular recording techniques on the acutely isolated SMA, membrane properties of the smooth muscle cells and the neuromuscular transmission in this preparation were investigated. With minimum tension and normal extracellular K(+) concentration (5 mM), the majority of muscle cells showed a resting potential near -80 mV and an input resistance of about 8 MOmega. V/I plot showed an inward rectification in these cells. Barium (50-500 microM) caused strong depolarization and an increase in input resistance. Transmural electrical stimulation evoked stimulation intensity-dependent depolarizations (2-31 mV) following a short latency ( approximately 20 ms). The evoked potential by a low intensity stimulus was completely blocked by 1 microM tetrodotoxin. The potential and a depolarization induced by norepinephrine (10 microM) was usually partially (40-90%) blocked by alpha-receptor antagonists prazosin and/or idazoxan with concentrations up to 1 microM. Action potentials were observed when the depolarization was more than -40 mV. It is concluded that SMA smooth muscle cells, similar to those in other brain small arteries, highly express inward rectifying potassium channels; the cells receive catecholaminergic innervation, and stimulation of the nerves elicited an excitatory junction potential that is partially mediated by adrenergic receptors.
内耳血液循环变化在听力功能的许多生理和病理状况中发挥重要作用。螺旋蜗轴动脉（SMA）是耳蜗的终末动脉。它被用酪氨酸羟化酶抗体免疫染色的神经纤维所环绕。通过在急性分离的SMA上使用细胞内记录技术，研究了该标本中平滑肌细胞的膜特性和神经肌肉传递。在最小张力和正常细胞外钾离子浓度（5 mM）下，大多数肌肉细胞的静息电位接近 -80 mV，输入电阻约为8 MΩ。V/I图显示这些细胞存在内向整流。钡（50 - 500 μM）引起强烈去极化并增加输入电阻。跨膜电刺激在短潜伏期（约20 ms）后诱发刺激强度依赖性去极化（2 - 31 mV）。低强度刺激诱发的电位被1 μM河豚毒素完全阻断。去甲肾上腺素（10 μM）诱导的电位和去极化通常被浓度高达1 μM的α受体拮抗剂哌唑嗪和/或咪唑克生部分阻断（40 - 90%）。当去极化超过 -40 mV时观察到动作电位。结论是，SMA平滑肌细胞与其他脑小动脉中的细胞类似，高度表达内向整流钾通道；这些细胞接受儿茶酚胺能神经支配，神经刺激引发兴奋性接头电位，该电位部分由肾上腺素能受体介导。
