Giaume C, Korn H
J Physiol. 1984 Nov;356:151-67. doi: 10.1113/jphysiol.1984.sp015458.
At the crayfish giant motor synapse, the lateral giant axon (l.g.a.) and the giant motor fibre (g.m.f.) form an electrotonic junction which exhibits two states of ionic coupling (Furshpan & Potter, 1959a; Giaume & Korn, 1983). Junctional conductance is low at resting membrane potentials (i.e. with lateral axon more negative than the motor fibre) and high when the polarity of the voltage difference (delta V) across the synapse is reversed. For these two states of conductance, junctional permeability was investigated using the intercellular tracer Lucifer Yellow. The dye was ionophoretically injected into either the presynaptic (l.g.a.) or the post-synaptic (g.m.f.) cell. In the high conductance state (delta V greater than 0), fluorescence was detected in both neurones whether Lucifer Yellow had been injected pre- or post-synaptically. By contrast, at the resting junctional polarization (delta V less than 0) Lucifer Yellow spread from the giant axon to the g.m.f., but not from the g.m.f. to the giant axons. These data demonstrate that dye transfer at the giant motor synapse, like ionic coupling, is sensitive to junctional polarization and is more marked in the high conductance state. Possible explanations for the asymmetry observed in the low conductance state are discussed.
在小龙虾巨大运动突触处，外侧巨大轴突（l.g.a.）和巨大运动纤维（g.m.f.）形成一个电突触，该电突触呈现两种离子偶联状态（Furshpan和Potter，1959a；Giaume和Korn，1983）。在静息膜电位时（即外侧轴突比运动纤维更负），突触连接电导较低，而当突触两端电压差（δV）的极性反转时，电导较高。针对这两种电导状态，使用细胞间示踪剂荧光黄研究了突触连接通透性。将染料通过离子电泳注入突触前（l.g.a.）或突触后（g.m.f.）细胞。在高电导状态下（δV大于0），无论荧光黄是注入突触前还是突触后，在两个神经元中均检测到荧光。相比之下，在静息突触极化状态下（δV小于0），荧光黄从巨大轴突扩散到g.m.f.，但不会从g.m.f.扩散到巨大轴突。这些数据表明，巨大运动突触处的染料转移与离子偶联一样，对突触极化敏感，且在高电导状态下更为明显。文中讨论了在低电导状态下观察到的不对称现象的可能解释。
