Numbers of presynaptic Ca ²⁺ channel clusters match those of functionally defined vesicular docking sites in single central synapses

Significance Release–docking sites have been considered from a morphological point of view as the sites where synaptic vesicles dock and fuse with the active-zone membrane. Functionally, docking sites limit the maximum number of vesicles released per action potential, determining synaptic strength. Until now it has not been possible to establish a clear link between morphological and functional aspects of docking sites in mammalian brain synapses. Recent data suggest that calcium channels form several clusters in the active zone. Here, we show that the number of the clusters matches that of functional docking sites and both parameters change in parallel with age and synaptic size. Based on these results we propose a one-to-one correspondence between docking sites and calcium channel clusters.