Baux G, Poulain B, Tauc L
J Physiol. 1986 Nov;380:209-26. doi: 10.1113/jphysiol.1986.sp016281.
The effects of hemicholinium-3 (HC-3) on cholinergic transmission were studied on central identified inhibitory (H-type post-synaptic cell, Cl- channels) and on excitatory (D-type post-synaptic cell, cationic channels) synapses of Aplysia californica. In the H-type post-synaptic cell, the amplitude and the decay time of miniature post-synaptic currents (m.p.s.c.s.) were calculated by statistical analysis of long duration induced post-synaptic current (l.d.i.p.s.c.) due to 3 s depolarizations of the presynaptic neurone in the presence of tetrodotoxin. On H-type receptors, with respect to acetylcholine (ACh), HC-3 acted as an agonist and a blocker whereas on D-type receptors, it acted only as a blocker. At low concentration of bath-applied HC-3, in the H-type synapse, the decay time of the evoked inhibitory post-synaptic current (i.p.s.c.) as well as that of the m.p.s.c. was lengthened. These changes were rapidly reversible by wash. The decay time of excitatory post-synaptic current (e.p.s.c.) at the D-type synapse was not affected. On the inhibitory synapse, HC-3 applied in the bath at the concentration of 10(-5) M, reduced considerably the size of the m.p.s.c.s whereas the evoked i.p.s.c.s and the l.d.i.p.s.c.s were only slightly affected pointing to an increase of the quantal content of both responses. After wash, both i.p.s.c.s and l.d.i.p.s.c.s showed a clear facilitation which persisted for several tens of minutes. The presence of presynaptic receptors was considered. Similar facilitation of e.p.s.c.s by HC-3 was observed at the D-type synapse. The comparison of the degree of depression by HC-3 of the m.p.s.c.s and of the responses to ionophoretically applied ACh, indicated that the size of the quantum was not changed. Intracellular injection of HC-3 into the presynaptic neurone of the H-type synapse led to a decrease of transmitter release which affected solely the quantal content of the responses. As the synaptic transmission could not be restored by injection of exogenous ACh into the presynaptic neurone, it was concluded that the depression of transmission was not due to a decrease of ACh synthesis.
研究了半胱氨酸-3（HC-3）对加州海兔中枢已确定的抑制性突触（H型突触后细胞，氯离子通道）和兴奋性突触（D型突触后细胞，阳离子通道）胆碱能传递的影响。在H型突触后细胞中，微小突触后电流（m.p.s.c.s.）的幅度和衰减时间通过对在河豚毒素存在下突触前神经元3秒去极化所诱发的长时间突触后电流（l.d.i.p.s.c.）进行统计分析来计算。在H型受体上，相对于乙酰胆碱（ACh），HC-3既作为激动剂又作为阻断剂，而在D型受体上，它仅作为阻断剂。在浴槽中施加低浓度的HC-3时，在H型突触中，诱发的抑制性突触后电流（i.p.s.c.）以及m.p.s.c.的衰减时间都延长了。这些变化通过冲洗可迅速逆转。D型突触处兴奋性突触后电流（e.p.s.c.）的衰减时间不受影响。在抑制性突触上，以10^(-5) M的浓度在浴槽中施加HC-3，可显著降低m.p.s.c.s的大小，而诱发的i.p.s.c.s和l.d.i.p.s.c.s仅受到轻微影响，这表明两种反应的量子含量增加。冲洗后，i.p.s.c.s和l.d.i.p.s.c.s都表现出明显的易化作用，这种作用持续数十分钟。考虑了突触前受体的存在。在D型突触处也观察到HC-3对e.p.s.c.s有类似的易化作用。比较HC-3对m.p.s.c.s的抑制程度和对离子电泳施加ACh的反应，表明量子大小没有改变。将HC-3细胞内注射到H型突触的突触前神经元中导致递质释放减少，这仅影响反应的量子含量。由于向突触前神经元注射外源性ACh不能恢复突触传递，因此得出结论，传递的抑制不是由于ACh合成减少所致。
