Department of Mathematical Sciences, NJIT, University Heights, Newark, NJ 07102-1982, USA.
Brain Res. 2011 Jun 29;1398:126-38. doi: 10.1016/j.brainres.2011.05.011. Epub 2011 May 12.
The number of Ca(2+) channels contributing to the exocytosis of a single neurotransmitter vesicle in a presynaptic terminal has been a question of significant interest and debate, and is important for a full understanding of localized Ca(2+) signaling in general, and synaptic physiology in particular. This is usually estimated by measuring the sensitivity of the neurotransmitter release rate to changes in the synaptic Ca(2+) current, which is varied using appropriate voltage-clamp protocols or via pharmacological Ca(2+) channel block under the condition of constant single-channel Ca(2+) current. The slope of the resulting log-log plot of transmitter release rate versus presynaptic Ca(2+) current is termed Ca(2+)current cooperativity of exocytosis, and provides indirect information about the underlying presynaptic morphology. In this review, we discuss the relationship between the Ca(2+) current cooperativity and the average number of Ca(2+) channels participating in the exocytosis of a single vesicle, termed the Ca(2+)channel cooperativity. We relate these quantities to the morphology of the presynaptic active zone. We also review experimental studies of Ca(2+) current cooperativity and its modulation during development in different classes of synapses.
在一个突触前末梢中，参与单个神经递质囊泡胞吐作用的 Ca(2+)通道数量一直是一个备受关注和争议的问题，对于全面理解局部 Ca(2+)信号转导，特别是突触生理学具有重要意义。通常通过测量神经递质释放率对突触 Ca(2+)电流变化的敏感性来估计，这可以通过适当的电压钳位协议来改变，或者在恒定的单通道 Ca(2+)电流条件下通过药理学 Ca(2+)通道阻断来实现。由此产生的递质释放率与突触前 Ca(2+)电流的对数-对数图的斜率被称为胞吐作用的 Ca(2+)电流协同性，它提供了关于潜在的突触前形态的间接信息。在这篇综述中，我们讨论了 Ca(2+)电流协同性与参与单个囊泡胞吐作用的 Ca(2+)通道的平均数量（称为 Ca(2+)通道协同性）之间的关系。我们将这些量与突触前活性区的形态联系起来。我们还回顾了不同类型突触中 Ca(2+)电流协同性及其在发育过程中的调节的实验研究。
