Spontaneous neurotransmitter release and Ca2+--how spontaneous is spontaneous neurotransmitter release?

Neurotransmitter release from neurons takes place at specialized structures called synapses. Action potential-evoked exocytosis requires Ca(2+) influx through voltage-gated Ca(2+) channels. Spontaneous vesicle fusion occurs both in the absence of action potentials and without any apparent stimulus a...