Presynaptic Direct Structure-Function Analysis

公认的神经肌肉接头化学传递模型是，当动作电位到达神经末梢时，电压敏感的钙通道开放，导致一系列事件，导致小泡与突触前膜融合，将其内容物释放到突触间隙。突触内活动区的数量，而不一定是突触本身的大小或数量，与突触功效的程度有关。除了结构因素外，其他因素对突触的有效性也有影响，但本研究的目的是关注结构相关性。研究单个突触的功能对于了解影响化学突触传递效果的机制是必不可少的。众所周知，小龙虾神经肌肉接头处突触结构的简单性及其释放的量化性质使我们能够评估运动神经末梢中的离散突触。通过使用现代统计技术分析量子电流轨迹的区域，注意到直接计数量子事件的金标准在确定释放位置的数量(N)和在这些位置释放的概率(P)时是不稳定的，当释放概率较低时。这种经典的方法即使在明显有多个站点在运行的情况下也会估计一个站点。这项调查中使用的现代方法估计了每个地点的释放概率(P)，以确定随着射击频率的增加是否招募了新的地点。所提出的研究通过各种统计方法直接将量子参数与突触结构相关联。一种已建立的从突触位置识别和记录的方法允许随后使用电子显微镜技术进行连续重建。因此，可以从电子显微镜照片中对同一区域进行连续切片和重建，以直接将功能与突触的超结构相关联。这一努力将使人们更清楚地了解影响突触有效性的结构元素所采用的机制，以及甲壳类动物递质释放的频率促进机制。

The accepted model for chemical transmission at the neuromuscular junction is that when an action potential reaches the nerve terminal, voltage-sensitive calcium channels open which leads to a cascade of events resulting in vesicles fusing with the presynaptic membrane to release their contents into the synaptic cleft. The number of active zones within synapses, and not necessarily the size or numbers of synapses per se, is correlated to the degree of synaptic efficacy. Additional factors besides structural elements have a role in synaptic efficacy, but the purpose of this study is to focus on structural correlations. Investigating the function of individual synapses is essential to understanding the mechanisms that influence the efficacy of chemical synaptic transmission. The known simplicity of the synaptic structure at the crayfish opener neuromuscular junction and its quantal nature of release allow an assessment of discrete synapses within the motor nerve terminals. By analyzing areas of a quantal current trace using modern statistical techniques, it is noted that the gold standard= of directly counting quantal events is unstable in determining the number of release sites (n) and the probability of release at these sites (p) when the probability of release is low. This classical approach estimates one site even when there are clearly multiple sites operating. Modern methods used in this investigation estimate the probability of release at each site (p) to determine whether new sites are recruited as the firing frequency is increased. The proposed investigations directly correlate quantal parameters by various statistical methods to synaptic structure. An established method of identifying and recording from a synaptic site allows for its subsequent serial reconstruction using electron microscopic techniques. Thus, the same region can be serial sectioned and reconstructed from electron micrographs to directly correlate function to synaptic ultra structure. This effort will provide a clearer understanding of the mechanisms employed by structural elements that influence synaptic efficacy and mechanisms underlying frequency facilitation of transmitter release in crustaceans.