How does Botox work?

What is the biological mechanism that makes Botox work? 

1. Nerve cells are known as neurons. Neurons instruct muscles to contract by releasing chemicals known as neurotransmitters across the neuromuscular junction, or the space between the end of a neuron and a muscle. When these neurotransmitters bind to the muscle cells, the muscle is instructed to contract.

2. Botulinum Toxin A, more commonly known commercially as Botox, is a neurotoxin. Neurotoxins block neurotransmitters from being released, preventing muscles from contracting. 

3. The type of neurotransmitter Botox blocks is called acetylcholine. Acetylcholine is stored inside of a neuron in molecules called vesicles. Vesicles are composed of a cell membrane, which protects its occupants from the cell environment. 

4. When the brain sends a signal to a neuron, instructing it to contract a muscle, the acetylcholine vesicle inside the neuron fuses with the membrane of the neuron, known as the presynaptic terminal, and the acetylcholine is released into the neuromuscular junction. 

5. Normally, the acetylcholine binds to the muscle and it’s instructed to contract. When Botox is present, it blocks the acetylcholine from being released and the muscle does not contract. 

6. The interactions described above take place in many neurons and muscle cells. As more Botox is injected, more acetylcholine is blocked and fewer muscle fibers are able to contract. Wrinkles form when muscles remain contracted from frequent use. With time, Botox relaxes the muscles to a point where the wrinkles are no longer visible. 

7. Frequent injections of Botox over time, cause muscles to become conditioned not to contract, preventing wrinkles from forming. Botox will last 3-4 months, depending on how quickly the patient’s body metabolizes the neurotoxin.