Why synapses release a certain amount of neurotransmitter is poorly understood. We combined patch-clamp electrophysiology with computer simulations to estimate how much glutamate is discharged at two distinct central synapses of the rat. We found that, regardless of some uncertainty over synaptic microenvironment, synapses generate the maximal current per released glutamate molecule while maximizing signal information content. Our result suggests that synapses operate on a principle of resource optimization.
The authors thank A. Silver, D. Kullmann and K. Volynski for comments, and
P. Michaluk for help with granule cell cultures. This work was supported by the
Wellcome Trust, UK Medical Research Council, European Research Council
Advanced Grant, and Biotechnology and UK Biological Sciences Research Council.