BOTOX - HOW IT WORKS
Under normal circumstances, a nerve comes into contact with a muscle at a neuromuscular junction. The nerve releases a neurotransmitter called acetylcholine.  Acetylcholine travels to the muscle resulting in contraction of the muscle.

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Botox keeps the neurotransmitter from stimulating the muscle, thereby keeping the muscle from contractin.

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This is the reason that Botox® is helpful for "dynamic" wrinkles, or wrinkles that result from the contraction of muscles. With time and with repeated injections of Botox®, the muscles that produce unwanted wrinkles will become smaller, and this may result in treatments that last longer or in treatments that require few units of the toxin.