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Any specific chemical agent (including acetylcholine, five amines, four amino acid s, two purines, and more than 28 peptides) released by a presynaptic cell, upon excitation, that crosses the synapse to stimulate or inhibit the postsynaptic cell. More than one may be released at any given synapse. The neurotransmitters released by presynaptic cells may modulate transmitter release from presynaptic cells. Nitric oxide may be a retrograde n., released from postsynaptic cells, to act on presynaptic cells. [neuro- + L. transmitto, to send across]
- cholinergic n. a n. formed in pre- and postganglionic synapses of the parasympathetic nervous system ( E.G., acetylcholine).
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neu·ro·trans·mit·ter .n(y)u̇r-ō-tran(t)s-'mit-ər, -tranz- n a substance (as norepinephrine or acetylcholine) that transmits nerve impulses across a synapse see FALSE NEUROTRANSMITTER
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n.
a chemical substance released from nerve endings to transmit impulses across synapse to other nerves and across the minute gaps between the nerves and the muscles or glands that they supply. Outside the central nervous system the chief neurotransmitter is acetylcholine; noradrenaline is released by nerve endings of the sympathetic system. In the central nervous system, as well as acetylcholine and noradrenaline, dopamine, serotonin, gamma-aminobutyric acid, the amino acid glutamate, and several other substances act as transmitters.
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neu·ro·trans·mit·ter (noor″o-transґmit-ər) any of a group of substances that are released on excitation from the axon terminal of a presynaptic neuron of the central or peripheral nervous system and travel across the synaptic cleft to either excite or inhibit the target cell. Among the many substances that have the properties of a neurotransmitter are acetylcholine, norepinephrine, epinephrine, dopamine, glycine, γ-aminobutyrate, glutamic acid, substance P, enkephalins, endorphins, and serotonin.Medical dictionary. 2011.