Ventriglia Francesco, Di Maio Vito
Istituto di Cibemetica E. Caianiello del CNR Via Campi Flegrei 34, Pozzuoli, NA 80078, Italy.
Biosystems. 2003 Sep;71(1-2):195-204. doi: 10.1016/s0303-2647(03)00117-5.
The postsynaptic response in glutamatergic synapses of hippocampus, produced by the release of a single presynaptic vesicle, shows a large variability in amplitude not only among the synapses, but also for a single synapse. A mathematical modelling based on a Brownian motion for the diffusion of glutamate molecules and receptor binding was applied to study the possible sources of the quantal variability. Detailed, geometric and functional, descriptions of the vesicle, of the fusion pore and of the synaptic cleft were used and quantal (or miniature) EPSCs were computed. Our results show non-saturation of AMPA receptors, attributable to the small number of molecules contained in the glutamate vesicles of hippocampus. NMDA receptor saturation was obtained rarely, only in very specific instances. We concluded that the lack of AMPA saturation and intrinsic random variations in basic presynaptic elements, such as the vesicle volume and the vesicle docking position, are the main causes of the observed stochastic variability of the quantal EPSC amplitude. Only minor effects can be ascribed to postsynaptic sources.
由单个突触前囊泡释放所产生的海马谷氨酸能突触中的突触后反应，不仅在不同突触之间，而且对于单个突触而言，其幅度都表现出很大的变异性。基于谷氨酸分子扩散和受体结合的布朗运动进行数学建模，以研究量子变异性的可能来源。使用了对囊泡、融合孔和突触间隙的详细的、几何和功能描述，并计算了量子（或微小）兴奋性突触后电流。我们的结果表明，由于海马谷氨酸囊泡中所含分子数量较少，AMPA受体未饱和。NMDA受体饱和很少出现，仅在非常特殊的情况下。我们得出结论，AMPA缺乏饱和以及基本突触前元件（如囊泡体积和囊泡对接位置）的内在随机变化，是观察到的量子兴奋性突触后电流幅度随机变异性的主要原因。突触后来源只能归因于较小的影响。
