Neurotransmitter Release
Neuronal communication is made possible by the release of neurotransmitters, which in turn depends on the fusion of neurotransmitter-laden synaptic vesicles at the ends of nerve cells. Synaptic vesicle fusion is triggered by an influx of Ca2+ ions into the neuron upon depolarization of the neuron, a process that initiates neurotransmission. Neurotransmitter release is quantized; that is, at most one synaptic vesicle fuses in the active zone upon an action potential. This process is controlled by several proteins, including SNAREs (soluble NSF [N-ethylmaleimide-sensitive factor] attachment protein receptors), the Ca2+sensor synaptotagmin-1, Munc18, Munc13, complexin, and the ATPase NSF, among others. Thus, neurotransmitter release is a biological phenomenon controlled by complex interactions between individual molecules. An understanding of the underlying molecular mechanisms requires methods that are capable of observing single vesicles and molecules.
