nevrotransmittermfrigjøring

Neurotransmitter release (nevrotransmittermfrigjøring) is the process by which chemical messengers are discharged from the presynaptic neuron into the synaptic cleft in response to an action potential. The released neurotransmitters diffuse across the cleft and interact with receptors on the postsynaptic cell, influencing its excitability and signaling. This fast form of cell-to-cell communication is essential for muscle contraction, sensory processing, and higher brain functions.

Mechanistically, an arriving action potential depolarizes the presynaptic terminal, opening voltage-gated calcium channels. The resulting influx of Ca2+ triggers rapid fusion of synaptic vesicles with the plasma membrane. Vesicle fusion is driven by a set of SNARE proteins that bridge the vesicle and plasma membranes, aided by a calcium sensor such as synaptotagmin. The fusion event releases neurotransmitter into the cleft by exocytosis.

After release, neurotransmitters interact with postsynaptic receptors (ionotropic and metabotropic). Terminators include reuptake into the presynaptic neuron or surrounding glia, enzymatic degradation in the synaptic cleft, and diffusion away from the site. The presynaptic terminal also recycles vesicle membranes through endocytosis to replenish the vesicle pool. Vesicular transporters load specific neurotransmitters into vesicles (for example, VGLUTs for glutamate, VGAT for GABA, VAChT for acetylcholine), and the readily releasable pool of vesicles mediates rapid transmission.

Neurotransmitter release is regulated in time and space, contributing to synaptic plasticity. Short-term modulation includes facilitation and depression during high-frequency activity, while long-term changes support learning and memory. The repertoire of neurotransmitters includes excitatory amino acids such as glutamate, inhibitory transmitters such as GABA and glycine, acetylcholine, monoamines (dopamine, norepinephrine, serotonin), neuropeptides, and others.