Okada Yasumasa, Kuwana Shun-ichi, Kawai Akira, Mückenhoff Klaus, Scheid Peter
Department of Medicine, Keio University Tsukigase Rehabilitation Center, Tsukigase 380-2, Izu City, Shizuoka-ken 410-3215, Japan.
Respir Physiol Neurobiol. 2005 Mar;146(1):21-32. doi: 10.1016/j.resp.2004.10.009.
The significance of extracellular potassium in central respiratory control was investigated using the isolated brainstem-spinal cord preparation of the neonatal rat. Depth profiles of extracellular potassium activity ([K+])ECF in the medulla were measured with ion-sensitive microelectrodes. Although [K+]ECF increased with depth in medullary tissue during control (4 mM) and low (1 mM) potassium concentration ([K+])CSF superfusion, this gradient disappeared with higher [K+]CSF. With low [K+]CSF (1 mM), respiratory CO2 responsiveness was abolished, and increased with high [K+]CSF (8 mM). Respiratory frequency (fR) was diminished at low [K+]CSF (1 mM), and increased with elevated [K+]CSF (8 and 16 mM); with yet higher [K+]CSF (32 mM) apnea occurred after a transient increase in fR. Perforated patch recording revealed that high [K+]ECF decreased membrane resistance, depolarized membrane potential, and increased firing frequency in most of the recorded medullary neurons. High [K+]ECF also increased excitatory and inhibitory post-synaptic potentials of medullary neurons and augmented the functional connectivity among neurons. It is concluded that [K+]ECF is of importance in the maintenance of respiratory rhythm and central chemosensitivity.
利用新生大鼠离体脑干-脊髓标本研究了细胞外钾在中枢呼吸控制中的意义。用离子敏感微电极测量延髓中细胞外钾活性（[K+]）ECF的深度分布。在对照（4 mM）和低（1 mM）钾浓度（[K+]）CSF灌注期间，延髓组织中的[K+]ECF随深度增加，但在较高[K+]CSF时这种梯度消失。低[K+]CSF（1 mM）时，呼吸对CO2的反应性消失，而高[K+]CSF（8 mM）时增加。低[K+]CSF（1 mM）时呼吸频率（fR）降低，高[K+]CSF（8和16 mM）时增加；更高[K+]CSF（32 mM）时，fR短暂增加后出现呼吸暂停。穿孔膜片钳记录显示，高[K+]ECF降低膜电阻、使膜电位去极化，并增加大多数记录的延髓神经元的放电频率。高[K+]ECF还增加延髓神经元的兴奋性和抑制性突触后电位，并增强神经元之间的功能连接性。得出的结论是，[K+]ECF在维持呼吸节律和中枢化学敏感性方面具有重要意义。
