Charpier S, Behrends J C, Triller A, Faber D S, Korn H
Laboratoire de Neurobiologie Cellulaire, Institut National de la Santé et de la Recherche Médicale U261, Institut Pasteur, Paris, France.
Proc Natl Acad Sci U S A. 1995 Jan 3;92(1):117-20. doi: 10.1073/pnas.92.1.117.
Simultaneous pre- and postsynaptic recordings from identified glycinergic inhibitory interneurons and the Mauthner cell showed that 25% of the afferents produced no or extremely small postsynaptic responses. Morphological determination of the number of contacts made by these cells on the Mauthner cell revealed a connectivity similar to that of functional neurons which always produce clear inhibitory postsynaptic potentials, suggesting that most of the endings, made by weak interneurons are silent. Intraaxonal injection of 4-aminopyridine or Ca2+ greatly enhanced transmission at functional connections but did not modify those which were ineffective. However, after eighth nerve tetanic stimuli, transmission at the weak connections was unmasked or enhanced for prolonged periods and was twice as likely to be potentiated, with a 6-fold greater mean enhancement than the potent ones. This result provides additional support for long-term potentiation of inhibitory synapses. Furthermore, weakly functional junctions represent a "reserve" pool which can be critical for the expression of plasticity within a network, and, consequently, for setting the threshold of reflex activities such as the escape reaction mediated by the Mauthner cell.
对已识别的甘氨酸能抑制性中间神经元和毛特纳细胞进行突触前和突触后同时记录，结果显示25%的传入神经未产生或仅产生极小的突触后反应。对这些细胞与毛特纳细胞形成的接触数量进行形态学测定，发现其连接性与那些总能产生明显抑制性突触后电位的功能性神经元相似，这表明大多数由弱中间神经元形成的末梢是沉默的。轴突内注射4-氨基吡啶或Ca2+可极大增强功能性连接的传递，但对无效连接无影响。然而，在第八对脑神经强直刺激后，弱连接的传递在较长时间内被揭示或增强，且其增强的可能性是强连接的两倍，平均增强幅度比强连接大6倍。这一结果为抑制性突触的长期增强提供了额外支持。此外，功能较弱的连接代表一个“储备”池，这对于网络内可塑性的表达可能至关重要，因此对于设定诸如毛特纳细胞介导的逃避反应等反射活动的阈值也可能至关重要。
