Title: Nanoscale distribution of presynaptic Ca(2+) channels and its impact on vesicular release during development.

Authors: Yukihiro Nakamura, Harumi Harada, Naomi Kamasawa, Ko Matsui, Jason S Rothman, Ryuichi Shigemoto, R Angus Silver, David A DiGregorio, Tomoyuki Takahashi

Journal, date & volume: Neuron, 2015 Jan 7 , 85, 145-58

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/25533484

Abstract
Synaptic efficacy and precision are influenced by the coupling of voltage-gated Ca(2+) channels (VGCCs) to vesicles. But because the topography of VGCCs and their proximity to vesicles is unknown, a quantitative understanding of the determinants of vesicular release at nanometer scale is lacking. To investigate this, we combined freeze-fracture replica immunogold labeling of Cav2.1 channels, local [Ca(2+)] imaging, and patch pipette perfusion of EGTA at the calyx of Held. Between postnatal day 7 and 21, VGCCs formed variable sized clusters and vesicular release became less sensitive to EGTA, whereas fixed Ca(2+) buffer properties remained constant. Experimentally constrained reaction-diffusion simulations suggest that Ca(2+) sensors for vesicular release are located at the perimeter of VGCC clusters (<30 nm) and predict that VGCC number per cluster determines vesicular release probability without altering release time course. This "perimeter release model" provides a unifying framework accounting for developmental changes in both synaptic efficacy and time course.