SYNTHESIS AND RELEASE OF ACETYLCHOLINE :::
Acetylcholine is synthesized inside the nerve fibre by the combination of choline with acetyl group obtained from acetylcoenzyme -A The reaction is catalyzed by enzyme choline acetyl transferace (CAT) or acetylase The rate limiting process is choline transport which is regulated by acetylcholine release The synthesis occurs throughout the nearone but it is rapid at the nerve terminal The synthesized acetylcholine is stored in synaptic vesicles (300-600 A) They travel through microtubules to reach to the nerve endings on depolarization of the nerve acetylcholine is released by excitation secretion coupling
The released acetylcholine acts on postsynaptic receptors muscarinic or nicotinic Muscarinic receptors are found in all types of smooth muscles heart and exocrine glands Nicotinic receptors are found in autonomic ganglia skeletal muscles and certain sites of central nervous system
The action of acetylcholine is terminated by its rapid hydrolysis through the enzyme cholinesterase There are two types of the cholinesterase enzyme :
1.True cholinesterase or acetylcholinesterase
2. Pseudocholinesterase or butylcholinesterase gives the differentiating points of these enzymes
TABLLE CHOLINESTERASES
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