neurotransmittersignalering

Neurotransmitter signaling is the process by which neurons communicate with one another and with other cell types through chemical messengers called neurotransmitters. In chemical synapses, an action potential arriving at the presynaptic terminal triggers the opening of voltage-gated calcium channels. The resulting calcium influx promotes the docking and fusion of neurotransmitter-containing vesicles with the presynaptic membrane, releasing their contents into the synaptic cleft. The neurotransmitters then diffuse across the gap and bind to receptors on the postsynaptic cell, producing rapid electrical changes or slower, modulatory effects.

Receptors fall into two broad classes. Ionotropic receptors are ligand-gated ion channels that mediate fast excitatory or inhibitory postsynaptic potentials. Metabotropic receptors are G protein-coupled receptors that initiate slower signaling cascades and longer-lasting physiological changes. Common neurotransmitters include glutamate (excitatory) and gamma-aminobutyric acid (GABA) (inhibitory) in the central nervous system, as well as acetylcholine, dopamine, serotonin, and norepinephrine, each engaging diverse receptor subtypes with distinct functional roles.

Signaling is terminated by several mechanisms. Reuptake transporters quickly remove many neurotransmitters from the synaptic cleft for reuse or degradation (for example, SERT, DAT, and NET for monoamines). Enzymatic breakdown, such as acetylcholinesterase for acetylcholine, also clears transmitter from the synapse. Glial cells contribute to clearance and metabolism, and neurotransmitters may also diffuse away from the synapse.

Neurotransmitter signaling underpins perception, movement, learning, and mood. Disturbances in signaling pathways are implicated in numerous disorders, and many drugs modify signaling by targeting receptors, transporters, or enzymes to treat conditions such as depression, schizophrenia, Parkinson disease, and Alzheimer's disease.