Acetylcholine chemical structure

Figure 1.1 The chemical structures of the main neurotransmitters. The relatively simple structure of acetylcholine, the monoamines and the amino acids contrasts with that of the peptides, the simplest of which are the enkephalins which consists of five amino acids substance P has eleven...

FIG. 18 Chemical structures of (a) acetylcholine chloride, (b) carbamylcholine chloride, (c) carba-myl-y8-methylcholine chloride, (d) acetyl-/i-methylcholine chloride, (e) tetramethylammonium chloride, (f) tetraethylamonium chloride, (g) succinylcholine chloride, (h) hexamethonium chloride, (i) scopolamine hydrobromide, 0 atropine sulfate, (k) homatropine hydrochloride, and (1) tubocurar-ine chloride. 

Cholinesterase inhibitors are a very important class of compounds related to cholinomimetics. Besides their therapeutic importance, a few of them are used as pesticides in agriculture, and the most toxic are used as chemical poisoning agents. Use of these substances is based on changes that take place after inactivation of cholinesterase or pseudocholinesterase (a less specific enzyme), i.e. effects observed as a result of acetylcholine buildup in neuro-effector compounds. Cholinesterase inhibitors are classified both by their chemical structure as well as by the type of their chemical reaction with the enzyme, which determines their temporary action. 

The direct-acting cholinomimetic drugs can be divided on the basis of chemical structure into esters of choline (including acetylcholine) and alkaloids (such as muscarine and nicotine). Many of these drugs have effects on both receptors acetylcholine is typical. A few of them are highly selective for the muscarinic or for the nicotinic receptor. However, none of the clinically useful drugs is selective for receptor subtypes in either class. 

The chemical structures of the stress neurotransmitter norepinephrine and the maintenance neurotransmitter acetylcholine. 

Remembrance of mechanisms past. Acetylcholinesterase converts acetylcholine into acetate and choline. Show the reaction as chemical structures ... 

Quaternlzation of these alkaloids removes much of their ability to penetrate into the central nervous system and to affect its functions. However, the same variation in chemical structure Increases the Weak ability of these materials to interfere with the action of acetylcholine at the motor end plates of skeletal muscles. 

Chemical structures of N,A/-dimethylaminoethanol (DMAE), choline and acetylcholine. 

Mechanistically, neuromuscular blockers combine with nicotinic receptors on the postsy-naptic membrane to block competitively acetylcholine (ACh) binding. This prevents conformational changes of, and sodium passage through, the ion channels in the membrane. Once applied to the neuromuscular end-plate, NMBAs desensitize the muscle cells to motor-nerve impulses and ACh. Chemical structures of acetylcholine and representative NMBAs are depicted in Figure 10.1. 

Abramson FB, Barlow RB, Mustafa MG, Stephenson RP. Relationships between chemical structure and affinity for acetylcholine receptors. Br J Pharmacol 1969 37 207-233. 

The susceptibility of agents to the action of enzymes is a major determinant of stability in tissues. Since enzyme activity is highly selective, subtle changes in the chemical structure can often lead to profound reductions in enzyme-mediated degradation. This approach is illustrated with examples involving analogs to acetylcholine and oligonucleotides. 

Choline esters are simply choline bound to an acetyl derivative by an ester bond. The ester bond of acetylcholine and related drugs is hydrolyzed by enzymes known as cholinesterases (e.g., acetylcholinesterase). Choline esters are more or less sensitive to cholinesterase deactivation depending on their chemical structure. 

The profound muscarinic activity of the alkaloid muscarine provided substantial rationale for synthesizing ethers of choline. Muscarine, which is obtained from the red variety of mushroom Amanita muscaria) and other mushrooms is one of the oldest known cholinergic agonists and is the compound tor which muscarinic receptors were named. It was used in many pharmacological experiments during the latter 19th century and the early part of the 20th century, and its use preceded the discovery and chemical characterization of acetylcholine (2). The chemical structure of muscarine (see above), however, was not completely characterized until 1957. Muscarine possesses three chiral centers (C2, C3, and C5). 

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