Largo C, Tombaugh G C, Aitken P G, Herreras O, Somjen G G
Depto de Investigación, Hospital Ramón y Cajal, Madrid, Spain.
J Neurophysiol. 1997 Jan;77(1):9-16. doi: 10.1152/jn.1997.77.1.9.
We investigated whether heptanol and other long-chain alcohols that are known to block gap junctions interfere with the generation or the propagation of spreading depression (SD). Waves of SD were triggered by micro-injection of concentrated KCl solution in stratum (s.) radiatum of CA1 of rat hippocampal tissue slices. DC-coupled recordings of extracellular potential (V0) were made at the injection and at a second site approximately 1 mm distant in st. radiatum and sometimes also in st. pyramidale. Extracellular excitatory postsynaptic potentials (fEPSPs) were evoked by stimulation of the Schaffer collateral bundle; in some experiments, antidromic population spikes were evoked by stimulation of the alveus. Bath application of 3 mM heptanol or 5 mM hexanol completely and reversibly prevented the propagation of the SD-related potential shift (delta V0) without abolishing the delta V0 at the injection site. Octanol (1 mM) had a similar but less reliably reversible effect. fEPSPs were depressed by approximately 30% by heptanol and octanol, 65% by hexanol. Antidromic population spikes were depressed by 30%. In isolated, patchclamped CA1 pyramidal neurons, heptanol partially and reversibly depressed voltage-dependent Na currents possibly explaining the slight depression of antidromic spikes and, by acting on presynaptic action potentials, also the depression of fEPSPs. Fluoroacetate (FAc), a putative selective blocker of glial metabolism, first induced multiple spike firing in response to single afferent volleys and then severely suppressed synaptic transmission (confirming earlier reports) without depressing the antidromic population spike. FAc did not inhibit SD propagation. The effect of alkyl alcohols is compatible with the idea that the opening of normally closed neuronal gap junctions is required for SD propagation. Alternative possible explanations include interference with the lipid phase of neuron membranes. The absence of SD inhibition by FAc confirms that synaptic transmission is not necessary for the propagation of SD, and it suggests that normally functioning glial cells are not essential for SD generation or propagation.
我们研究了已知可阻断缝隙连接的庚醇和其他长链醇是否会干扰扩散性抑制（SD）的产生或传播。通过在大鼠海马组织切片CA1区辐射层微量注射浓缩氯化钾溶液来引发SD波。在注射部位以及辐射层中距离约1mm的第二个部位，有时也在锥体层进行细胞外电位（V0）的直流耦合记录。通过刺激Schaffer侧支束诱发细胞外兴奋性突触后电位（fEPSP）；在一些实验中，通过刺激海马槽诱发逆向群体峰电位。浴用3mM庚醇或5mM己醇可完全且可逆地阻止与SD相关的电位变化（ΔV0）的传播，但不会消除注射部位的ΔV0。1mM辛醇有类似但可逆性较差的作用。庚醇和辛醇使fEPSP降低约30%，己醇使其降低65%。逆向群体峰电位降低30%。在分离的、膜片钳记录的CA1锥体神经元中，庚醇部分且可逆地抑制电压依赖性钠电流，这可能解释了逆向峰电位的轻微降低，并且通过作用于突触前动作电位，也解释了fEPSP的降低。氟乙酸（FAc）是一种假定的胶质细胞代谢选择性阻滞剂，它首先在对单个传入冲动的反应中诱导多次峰发放，然后严重抑制突触传递（证实了早期报告），但不抑制逆向群体峰电位。FAc不抑制SD传播。烷基醇的作用与以下观点一致，即SD传播需要打开通常关闭的神经元缝隙连接。其他可能的解释包括对神经元膜脂质相的干扰。FAc不抑制SD，这证实了突触传递对于SD传播不是必需的，并且表明正常功能的胶质细胞对于SD的产生或传播不是必需的。
