Three-Dimensional Reconstruction of a Calyx of Held and Its Postsynaptic Principal Neuron in the Medial Nucleus of the Trapezoid Body

摘要: The three-dimensional morphology of the axosomatic synaptic structures between a calyx Held and principal neuron in medial nucleus trapezoid body (MNTB) brainstem young postnatal day 9 rats was reconstructed from serial ultrathin sections. In apposition zone two types membrane specializations were identified: contacts (SCs) with active zones (AZs) their associated postsynaptic densities (PSDs) constituted approximately 35% (n = 554) specializations; remaining 65% 1010) puncta adherentia (PA). Synaptic comprised 5% area presynaptic membranes. A SC had an average 0.100 microm(2), nearest neighbors separated, on average, by 0.59 microm. Approximately one-half vesicles clustered within distance 200 nm AZ area, cluster consisting 60 52 SCs). per "anatomically docked." Comparing geometry structure its previously studied functional properties, we find that during single action potential (AP) (1) AZs release transmitter quantum, (2) number SCs anatomically docked is comparable low estimates readily releasable pool (RRP) quanta, (3) broad distribution PSD areas [coefficient variation (CV) 0.9] likely to contribute large variability miniature EPSC peaks. synapse suggests each hundreds independently size rising phase AP.