Okano K
Department of Physiology, Teikyo University School of Medicine, Tokyo, Japan.
Brain Res. 1988 Aug 2;457(1):89-97. doi: 10.1016/0006-8993(88)90060-1.
In the Plotosus electroreceptor, strong brief excitatory pulses to the ampulla induced bi-phasic postsynaptic potential (PSP), externally recorded in the afferent nerves, a fast PSP during the pulse and a later slow PSP. Both PSPs increased in size on increasing stimulus intensity, with a lower saturation level for the slow PSP. Time to peak for the fast PSP gradedly decreased to below 10 ms on stronger stimuli, while in contrast that for the slow PSP increased to over 100 ms. The two PSPs were also readily distinguished pharmacologically. Some Glu antagonists, kynurenic acid and gamma-DGG, suppressed the slow PSP, but had little effect on the fast PSP. The suppression was dose-dependent and reversible over the entire range of input-output relations. In addition, L-aspartate at 100-300 microM markedly prolonged the slow PSP, but had little effect on the fast PSP. These results indicate two distinct populations of postsynaptic receptors: one for the slow PSP pharmacologically corresponding to a Glu receptor, and the other for the fast PSP of still unknown property. The two PSPs, though discriminated under specified stimulus conditions, seem to be involved also in the synaptic responses of longer duration in general.
在须鳗电感受器中，对壶腹的强而短暂的兴奋性脉冲会诱发双相突触后电位（PSP），该电位可在传入神经中进行外部记录，脉冲期间为快速PSP，随后为缓慢PSP。随着刺激强度的增加，两种PSP的幅度均增大，缓慢PSP的饱和水平较低。在较强刺激下，快速PSP的峰值时间逐渐缩短至10毫秒以下，而缓慢PSP的峰值时间则增加至100毫秒以上。这两种PSP在药理学上也很容易区分。一些谷氨酸拮抗剂，犬尿氨酸和γ-DGG，可抑制缓慢PSP，但对快速PSP几乎没有影响。这种抑制作用在整个输入-输出关系范围内是剂量依赖性的且可逆。此外，100-300微摩尔的L-天冬氨酸可显著延长缓慢PSP，但对快速PSP几乎没有影响。这些结果表明存在两种不同的突触后受体群体：一种是对应于谷氨酸受体的缓慢PSP的药理学受体，另一种是性质仍未知的快速PSP的受体。这两种PSP虽然在特定刺激条件下可以区分，但似乎通常也参与持续时间更长的突触反应。
