Korn H, Axelrad H
Proc Natl Acad Sci U S A. 1980 Oct;77(10):6244-7. doi: 10.1073/pnas.77.10.6244.
Monosynaptic activation of cerebellar Purkinje cells by a volley of parallel-fiber impulses is followed by a powerful disynaptic chemical inhibition mediated by molecular layer interneurons, including basket cells. Active zone established by basket preterminal axons on the body surface of the Purkinje cell account for this inhibition. However, morphological studies indicate that branches of the presynaptic fibers further descend along the initial segment of the Purkinje axon. Terminals from several basket cells converge and encapsulate each initial segment with a peculiar architectural structure that is reminiscent of that characterizing the axon cap of the teleost Mauthner cell. Because no function has yet been attributed to this pinceau, we have reanalyzed the successive Purkinje cell responses to activation of their presynaptic elements. Electrophysiological data provided by field-potential and single-unit measurements indicate that the classical phases of excitation and inhibition after a parallel-fiber volley are preceded by a brief inhibition of the Purkinje cells. Transmembrane hyperpolarizing potentials that exhibit the characteristics expected of electrically mediatd potentials underlie this early phase of inhibition; their properties are consistent with the hypothesis that they are generated by currents through terminals of nearby basket cells. Therefore, these hyperpolarizations, which are similar in their mechanism of generation to those described in the Mauthner cell system, represent a known case of electrical inhibition in the mammalian central nervous system.
平行纤维冲动群对小脑浦肯野细胞的单突触激活之后，会接着出现由分子层中间神经元（包括篮状细胞）介导的强大双突触化学抑制。篮状细胞终末前轴突在浦肯野细胞体表形成的活性区导致了这种抑制。然而，形态学研究表明，突触前纤维的分支会沿着浦肯野轴突的起始段进一步下行。来自多个篮状细胞的终末会聚并以一种特殊的结构包裹每个起始段，这种结构让人联想到硬骨鱼莫特纳尔细胞的轴突帽。由于尚未确定这种“束状结构”的功能，我们重新分析了浦肯野细胞对其突触前成分激活的连续反应。场电位和单单位测量提供的电生理数据表明，平行纤维冲动群后经典的兴奋和抑制阶段之前，浦肯野细胞会先出现短暂抑制。跨膜超极化电位具有电介导电位预期的特征，是这种早期抑制阶段的基础；其特性与它们由附近篮状细胞终末电流产生的假设一致。因此，这些超极化在产生机制上与莫特纳尔细胞系统中描述的类似，代表了哺乳动物中枢神经系统中一种已知的电抑制情况。
