Transmitter timecourse in the synaptic cleft: its role in central synaptic function
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Updated: Nov 5, 2026

Transmission Electron Microscopy as the Visualization Technique for Analysis of Circadian Synaptic Plasticity in the Mouse Barrel Cortex
Published on: August 19, 2025
1John Curtin School of Medical Research, Australian National University, Canberra, Australia.
Abstract:
The speed of clearance of transmitter from the cleft influences many aspects of synaptic function, including the timecourse of the postsynaptic response and the peak postsynaptic receptor occupancy. The timecourse of transmitter clearance can be estimated either by detailed theoretical modelling, or from the attenuation of synaptic transmission produced by a low-affinity competitive antagonist. These approaches have been applied to several classes of central synapse, and results obtained are in broad agreement. The average concentration of transmitter peaks in the range 1-5 mM, and clearance is biphasic, with time constants of approximately 100 microseconds and 2 ms. The pulse of transmitter, although very brief, can prolong the timecourse of the fastest AMPA synaptic currents, and is sufficient to saturate postsynaptic GABA, glycine or NMDA receptors.
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