Cholinergic neurotransmission (1)

1. Cholinergic transmission is mediated by acetylcholine (ACh) at various sites including parasympathetic neuroeffector junctions, autonomic ganglia, adrenal medulla, somatic myoneural junctions, and certain CNS regions. 2. ACh is synthesized from choline and acetyl-CoA in nerve terminals, stored in vesicles, and released into the synaptic cleft upon arrival of an action potential. It is then broken down by acetylcholinesterase. 3. There are muscarinic and nicotinic cholinergic receptors. Muscarinic receptors are G-protein coupled and mediate actions like smooth muscle contraction and gland secretion. Nicotinic receptors are