Chvátal A, Jendelová P, Kríz N, Syková E
Institue of Physiological Regulations, Czechoslovak Academy of Sciences, Prague.
Physiol Bohemoslov. 1988;37(3):203-12.
Double-barrel ion-sensitive microelectrodes were used to measure activity-related changes in extracellular pH (pHe), potassium and calcium concentration ([K+]e and [Ca2+]e) in the spinal dorsal horns of frogs. Repetitive stimulation (30-100 Hz) of the dorsal root evoked transient acidification in the lower dorsal horn by 0.25 pH units, which was accompanied by an increase in [K+]e by 4-5 mmol/l and a decrease in [Ca2+]e by 0.5 mmol/l. The pHe changes were found to have a typical depth profile and increased with the stimulation frequency, intensity and duration. The maximum of pHe changes was reached in 25-30 s of stimulation, and when stimulation continued further no greater pHe changes were achieved. Similarly as the K+ and Ca2+ transients, the pHe reached a ceiling level, which was 0.2-0.25 pH units more acid than the pH of the Ringer solution. The poststimulation K+ undershoot below the resting K+ level (3 mmol/l) was accompanied by an alkaline shift before the original pH base line. The rise time of the pHe changes was slower than that of [K+]e and [Ca2+]e changes. However, the redistribution of all the ionic changes had a similar time course. The clearance of changes in [K+]e and pHe was slowed by ouabain. The depression of the acid shift required higher concentrations of ouabain than the depression of the alkaline shifts. Acetazolamide, a carbonic anhydrase inhibitor, depressed the acid and enhanced the alkaline shift. Superfusion of the cord with elevated [K+]e was accompanied by a prompt and progressive acid shift, the lowering of [K+]e by an alkaline shift. The stimulus-evoked K+ increase and acid shift were depressed during the elevated [K+]e, while the alkaline shift was enhanced. Spontaneous elevations of [K+]e were accompanied by acid shifts of a similar time course. The results are discussed in terms of stimulus-evoked changes in extracellular strong ion differences [SID]e, and of their possible physiological significance.
使用双管离子敏感微电极来测量青蛙脊髓背角中与活动相关的细胞外pH值（pHe）、钾离子和钙离子浓度（[K+]e和[Ca2+]e）的变化。对背根进行重复刺激（30 - 100 Hz）会使下背角出现短暂酸化，pH值下降0.25个单位，同时[K+]e升高4 - 5 mmol/l，[Ca2+]e降低0.5 mmol/l。发现pHe变化具有典型的深度分布，并随刺激频率、强度和持续时间增加。在刺激25 - 30秒时达到pHe变化的最大值，继续刺激时pHe不再有更大变化。与K+和Ca2+瞬变情况类似，pHe达到一个上限水平，比林格溶液的pH值酸性高0.2 - 0.25个pH单位。刺激后K+低于静息K+水平（3 mmol/l）的下冲伴随着在原始pH基线之前的碱化转变。pHe变化的上升时间比[K+]e和[Ca2+]e变化的上升时间慢。然而，所有离子变化的重新分布具有相似的时间进程。哇巴因会减缓[K+]e和pHe变化的清除。抑制酸转变所需的哇巴因浓度高于抑制碱化转变所需的浓度。碳酸酐酶抑制剂乙酰唑胺会抑制酸转变并增强碱化转变。用升高的[K+]e对脊髓进行灌流会伴随着迅速且逐渐的酸转变，降低[K+]e则会伴随着碱化转变。在[K+]e升高期间，刺激诱发的K+增加和酸转变受到抑制，而碱化转变增强。[K+]e的自发升高伴随着相似时间进程的酸转变。根据刺激诱发的细胞外强离子差[SID]e的变化及其可能的生理意义对结果进行了讨论。
