Deitmer J W, Eckert R, Schlue W R
Can J Physiol Pharmacol. 1987 May;65(5):934-9. doi: 10.1139/y87-149.
The intracellular free Ca concentration was measured in invertebrate neurones using single-barrelled and double-barrelled neutral-carrier microelectrodes. The electrodes were calibrated in solutions containing different Ca concentrations between 1 mM and 0.01 microM. The electrode responses were also tested at different ionic strengths and at varying Na concentrations. The electrodes responded with 25-30 mV per 10-fold change in Ca concentration between 1 mM and 1 microM and with 10-25 mV between 1 and 0.1 microM Ca. The intracellular free Ca concentration was measured to be between 0.1 and 0.7 microM in the neurones. The changes of intracellular Ca in identified voltage-clamped neurones of Aplysia californica were recorded during iontophoretic injections of Ca2+ or EGTA. The decrease of intracellular Ca following EGTA injection was correlated with the suppression of the Ca-dependent K current and with the reduction of Ca-induced inactivation of voltage-dependent Ca current. In identified neurones of the leech Hirudo medicinalis a reversible increase of intracellular Ca2+ was recorded after inhibition of the Na-K pump, either by addition of ouabain (0.5 mM) or by lowering the external K concentration (0.2 mM). This rise in intracellular Ca2+ did not occur, and was even reversed, in the absence of external Na, suggesting the existence of Na-Ca exchange across the leech neuronal membrane.
使用单管和双管中性载体微电极测量无脊椎动物神经元中的细胞内游离钙浓度。电极在含有1 mM至0.01 microM不同钙浓度的溶液中进行校准。还在不同离子强度和不同钠浓度下测试电极响应。在1 mM至1 microM的钙浓度之间，电极对钙浓度每10倍变化的响应为25 - 30 mV，在1至0.1 microM钙之间为10 - 25 mV。测得神经元中的细胞内游离钙浓度在0.1至0.7 microM之间。在离子电渗注射Ca2+或EGTA期间，记录了加州海兔已识别的电压钳制神经元中细胞内钙的变化。注射EGTA后细胞内钙的减少与钙依赖性钾电流的抑制以及电压依赖性钙电流的钙诱导失活的减少相关。在医蛭已识别的神经元中，通过添加哇巴因（0.5 mM）或降低外部钾浓度（0.2 mM）抑制钠钾泵后，记录到细胞内Ca2+可逆性增加。在没有外部钠的情况下，细胞内Ca2+的这种升高不会发生，甚至会逆转，这表明水蛭神经元膜上存在钠钙交换。
