Mode of Action
In a synapse, action potentials are conducted along motor nerves to their terminals where they initiate a Ca2+ influx and the release of acetylcholine (ACh). The ACh diffuses across the synaptic cleft and binds to receptors on the post synaptic membrane, causing an influx of Na+ and K+ ions, resulting in depolarization. If large enough, this depolarization results in an action potential. To prevent constant stimulation once the ACh is released, an enzyme called acetylcholinesterase is present in the endplate membrane close to the receptors on the post synaptic membrane, and quickly hydrolizes ACh.
Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft, thus slowing down the hydrolysis of acetylcholine. It is a quaternary carbamate inhibitor of cholinesterase that does not cross the blood–brain barrier which carbamylates about 30% of peripheral cholinesterase enzyme. The carbamylated enzyme eventually regenerates by natural hydrolysis and excess ACh levels revert to normal.
Read more about this topic: Pyridostigmine
Famous quotes containing the words mode of, mode and/or action:
“Curiously enough, it seems to be only in describing a mode of language which does not mean what it says that one can actually say what one means.”
—Paul Deman (1919–1983)
“The mode of founding a college is, commonly, to get up a subscription of dollars and cents, and then, following blindly the principles of a division of labor to its extreme,—a principle which should never be followed but with circumspection,—to call in a contractor who makes this a subject of speculation,... and for these oversights successive generations have to pay.”
—Henry David Thoreau (1817–1862)
“It was the feeling of a passenger on an ocean steamer whose mind will not give him rest until he has been in the engine-room and talked with the engineer. She wanted to see with her own eyes the action of primary forces; to touch with her own eyes the action of primary forces; to touch with her own hand the massive machinery of society; to measure with her own mind the capacity of the motive power. She was bent upon getting to the heart of the great American mystery of democracy and government.”
—Henry Brooks Adams (1838–1918)