Neurotransmittorer

Neurotransmittorer, often called neurotransmitters in English, are chemical messengers that enable signal transmission between neurons and other cells at chemical synapses. They are released from presynaptic terminals in response to an action potential and act on receptors on the postsynaptic cell to influence membrane potential and cellular activity.

They are broadly classified as small-molecule neurotransmitters (such as acetylcholine, glutamate, GABA, glycine, dopamine, norepinephrine, serotonin) and neuropeptides (such as substance P, vasopressin, endorphins). Some also function as modulators, influencing the strength or probability of transmission rather than triggering fast postsynaptic responses.

Synthesis occurs in the presynaptic neuron, and neurotransmitters are stored in synaptic vesicles. When an action potential arrives, calcium influx triggers vesicle fusion and release by SNARE proteins. The neurotransmitter binds to ionotropic receptors (ligand-gated ion channels) or metabotropic receptors (G-protein-coupled), producing fast or slow postsynaptic effects.

Removal from the synaptic cleft occurs mainly by reuptake into the presynaptic neuron or neighboring glial cells, enzymatic degradation (for example acetylcholinesterase for acetylcholine, monoamine oxidase and catechol-O-methyltransferase for monoamines), or diffusion. Autoreceptors on the presynaptic terminal regulate release and synthesis.

Dysfunction or imbalance of neurotransmittorer systems is linked to many conditions, including depression, schizophrenia, Parkinson's disease, and epilepsy. Pharmacological manipulation of neurotransmitters, via agonists, antagonists, uptake inhibitors, or enzyme inhibitors, underpins many treatments and research in neurology and psychiatry.