Hablitz J J, Andersen P
Exp Brain Res. 1982;47(1):154-7. doi: 10.1007/BF00235899.
Intra- and extracellular recordings were obtained from the CA1 region of guinea pig hippocampal slices maintained in vitro. We studied the effect of reducing the extracellular sodium concentration on penicillin-induced epileptiform responses. In control experiments, Tris and choline were assayed as sodium substitutes. Choline was found unsuitable, since it induced repetitive firing in the absence of any convulsant agent. Replacement of 50% of the extracellular sodium ( [Na+]o) with Tris reduced the amplitude of the presynaptic fiber volley, the field EPSP, and the population spike. Intracellular studies showed that when [Na+]o was lowered, action-potential amplitudes were reversibly depressed by an amount close to that predicted by the Nernst relation. Orthodromically elicited epileptiform discharges, induced by penicillin, were reduced in a low-sodium medium when constant stimulus currents were employed. If orthodromic stimulus strengths in normal and low-sodium states were equated on the basis of the field-EPSP amplitude, no significant diminution of the depolarizing-wave component of the epileptiform response was observed. These results suggest that a synaptic component underlies penicillin-induced epileptiform discharges.
在体外维持的豚鼠海马切片的CA1区进行细胞内和细胞外记录。我们研究了降低细胞外钠浓度对青霉素诱导的癫痫样反应的影响。在对照实验中，测定了Tris和胆碱作为钠替代物的效果。发现胆碱不合适，因为它在没有任何惊厥剂的情况下会诱发重复放电。用Tris替代50%的细胞外钠（[Na+]o）会降低突触前纤维峰电位、场兴奋性突触后电位（field EPSP）和群体峰电位的幅度。细胞内研究表明，当[Na+]o降低时，动作电位幅度会可逆性降低，降低幅度接近能斯特关系预测的幅度。当使用恒定刺激电流时，在低钠培养基中，青霉素诱发的顺向性癫痫样放电减少。如果根据场兴奋性突触后电位幅度使正常和低钠状态下的顺向性刺激强度相等，则未观察到癫痫样反应的去极化波成分有明显减小。这些结果表明，青霉素诱导的癫痫样放电有一个突触成分。
