The nicotinic acetylcholine receptor is an ionotropic receptor that can be activated by nicotine, a stimulant drug found in cigarettes. Additionally, ?-bungarotoxin, a neurotoxin found in the venom of some snakes, binds preferentially and tightly to the closed conformation of the receptors. Another drug, donepezil, is a potent acetylcholinesterase inhibitor used to treat patients with Alzheimer's disease. If applied at a neuromuscular junction, indicate whether each of the compounds (1) acetylcholine, (2) nicotine, (3) ?-bungarotoxin, and (4) donepezil would enhance (E) or suppress (S) the Ca²⁺influx in the muscle cells. Your answer would be a four-letter string composed of letters E and S only, e.g. EESS.

Question

Quizplus · Accepted Answer

The Ca²⁺ influx in the muscle cell is stimulated by acetylcholine or nicotine through the opening of ionotropic acetylcholine receptors. Acetylcholinesterase lowers the concentration of acetylcholine at the neuromuscular junction, and its inhibitor would therefore also enhance Ca²⁺influx mediated by acetylcholine. In contrast, by favoring the closed state of the channels, ?-bungarotoxin suppresses the influx and can cause paralysis.

The Nicotinic Acetylcholine Receptor Is an Ionotropic Receptor That Can