NUMERICAL RECONSTRUCTION OF THE QUANTAL EVENT AT NICOTINIC SYNAPSES

被引:154
作者
WATHEY, JC [1 ]
NASS, MM [1 ]
LESTER, HA [1 ]
机构
[1] CALTECH,DIV BIOL,PASADENA,CA 91125
关键词
D O I
10.1016/S0006-3495(79)85208-X
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
To test our present quantitative knowledge of nicotinic transmission, we reconstruct the postsynaptic conductance change that results after a presynaptic nerve terminal liberates a quantum of acetylcholine (ACh) into the synaptic cleft. The theory assumes that ACh appears suddenly in the cleft and that is subsequent fate is determined by radial diffusion, by enzymatic hydrolysis, and by binding to receptors. Each receptor has one channel and two ACh binding sites; the channel opens when both sites are occupied and the rate-limiting step id the binding and dissociation of the second ACh molecule. The calculations reproduce the experimentally measured growth phase (200 microseconds), peak number of open channels (2,000), and exponential decay phase. The time constant of the decay phase exceeds the channel duration by approximately equal to 20%. The normal event is highly localized: at the peak, two-thirds of the open channels are within an area of 0.15 micrometer 2. This represents 75% of the available channels within this area. The model also simulates voltage and temperature dependence and effects of inactivating esterase and receptors. The calculations show that in the absence of esterase, transmitter is buffered by binding to receptors and the postsynaptic response can be potentiated. © 1979, The Biophysical Society. All rights reserved.
引用
收藏
页码:145 / 164
页数:20
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