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Major neurotransmitters in the autonomic nervous system
What are the major important neurotransmitters and their receptors in the autonomic nervous system.
Acetylcholine (ACh)
This is the neurotransmitter for all preganglionic and for the parasympathetic postganglionic neurons.
ACh receptors in the autonomic nervous system are divided into nicotinic and muscarinic types.
Nicotinic receptors, of which multiple subtypes are found mainly in the ganglia, are ligand-gated sodium channels that mediate fast responses.
Muscarinic receptors mediate slower responses and are found mostly throughout autonomic effector tissues.
Five subtypes of muscarinic receptors (M 1 to M 5 ) have been identified.
Norepinephrine (NE)
This is the neurotransmitter for most sympathetic postganglionic fibers. Adrenergic receptors are divided into alpha (α 1 and α 2 ) and beta (β 1 , β 2 , and β 3 ) types and are localized in various autonomic effector tissues.
Sweat glands are innervated by sympathetic cholinergic nerves.
