Incomplete vesicular docking limits synaptic strength under high release probability conditions

eLife

Laura C Gomez¹  Alain Marty¹  Van Tran¹  Gerardo Malagon²  Takafumi Miki³ 

[1] Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France;Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France;Department of Cell Biology and Physiology, Washington University, St. Louis, United States;Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France;Graduate School of Brain Science, Doshisha University, Kyoto, Japan;

关键词: synapse;    release site;    calcium concentration;    Rat;   

DOI  :  10.7554/eLife.52137

来源: publisher

【 摘 要 】

Central mammalian synapses release synaptic vesicles in dedicated structures called docking/release sites. It has been assumed that when voltage-dependent calcium entry is sufficiently large, synaptic output attains a maximum value of one synaptic vesicle per action potential and per site. Here we use deconvolution to count synaptic vesicle output at single sites (mean site number per synapse: 3.6). When increasing calcium entry with tetraethylammonium in 1.5 mM external calcium concentration, we find that synaptic output saturates at 0.22 vesicle per site, not at 1 vesicle per site. Fitting the results with current models of calcium-dependent exocytosis indicates that the 0.22 vesicle limit reflects the probability of docking sites to be occupied by synaptic vesicles at rest, as only docked vesicles can be released. With 3 mM external calcium, the maximum output per site increases to 0.47, indicating an increase in docking site occupancy as a function of external calcium concentration.

【 授权许可】

CC BY