Characteristics of quantal release of glutamate and GABA in synapses between retinal ganglion cells and superior colliculus neurons in coculture

: We investigated features of quantal release of glutamate and GABA in synapses between retinal ganglion cells (RGC) and superior colliculus (SC) neurons in coculture using dual patch-clamp technique. The main quantal characteristics of neurotransmitters release were defined on the basic of quantal analysis. Number of released quanta distributions for both neurotransmitters were corresponded to the binomial law. It was shown that evoked postsynaptic currents (PSC) in SC neurons as response to generation of action potential (AP) in RGC were mediated by simultaneous release at least from 2 to 14 quanta of glutamate and 2 quanta of GABA. Thereby high efficacy of excitatory and inhibitory signals transmission is guaranteed in retinocollicular projections. It is supposed that multiquantal character of the neurotransmitters release can be related to simultaneous involvement of several closely adjacent excited terminals, each of which possesses one active zone, or by one terminal with several.