How do botulinum toxins work?

Injections of botulinic toxinor Botoxare one of the most widely used aesthetic treatments for reducing wrinkles. Although they are widely used, the question that many people ask themselves remains: how does botulinum toxin really work? Not everyone is familiar with its mechanism of action at cellular and muscular level, which means that the results are visible and long-lasting.

In this article, we will explain in detailow botulinum toxin works on muscles and neurons and how this translates into a reduction in wrinkles and muscle contractions.

What is botulinum toxin?

La botulinic toxin is a neurotoxin produced by the bacterium Clostridium botulinum. There are different types of this toxin, but the form most commonly used for medical and cosmetic purposes is type A (Botox, Dysport, Xeomin).

The nature of botulinum toxin

Botulinum toxin is one of the most powerful substances known to block the transmission of nerve signals. In other words, it acts as an inhibitor of communication between nerves and muscles, causing temporary paralysis of the muscles in the targeted areas.

How does nerve transmission in muscles work?

To understand the mechanism of action of botulinum toxin, it is essential to understand how muscles normally contract.

  • Muscle movement is controlled by the nervous system. When a signal is sent from the brain or spinal cord to move a muscle, it travels along a motor neuron until it reaches the junction between the neuron and the muscle, called the neuromuscular junction.
  • At this junction, the nerve releases a neurotransmitter called acetylcholine into a small area called the synaptic cleft (the space between the nerve and the muscle cell).
  • Acetylcholine binds to specific receptors on the surface of muscle cells, triggering their contraction.

Mechanism of action of botulinum toxin

Type A botulinum toxin acts directly on this nerve transmission process, blocking the release of acetylcholine and inhibiting muscle contraction.

  • Inhibition of acetylcholine release: botulinum toxin acts at nerve endings by blocking the release of acetylcholine. It does this by cleaving specific proteins in the vesicles containing acetylcholine, preventing these vesicles from fusing with the nerve cell membrane. In other words, the toxin 'deactivates' the acetylcholine release mechanism.
    Without this neurotransmitter, the muscle is no longer able to receive the signal it needs to contract. The muscle therefore remains relaxed.
  • Temporary effect on muscles: the effect of botulinum toxin is temporary, as the nerve cells eventually generate new endings capable of releasing acetylcholine. This means that the results of the injection generally last between 3 and 6 monthsdepending on the area treated and the patient's metabolism.
  • Precise targeting of muscles: during a botulinum toxin injection, the doctor targets specific muscles to relax only the areas responsible for expression lines. For example, to treat forehead wrinkles or crow's feet, botulinum toxin is injected into the muscles responsible for repeated contractions in these areas. The result is smooth skin in the injected area, while maintaining a natural facial expression.

 

Effect on expression lines

Expression lines appear as a result of repeated contractions of the skin's underlying muscles. These wrinkles are particularly visible on :

By temporarily relaxing the muscles, botulinum toxin prevents the repetitive contractions that create and accentuate wrinkles over time. The skin above the relaxed muscles becomes smoother.

Muscle relaxation process

The muscle relaxation caused by botulinum toxin is not immediate.

Here's how the process works:
Injection: botulinum toxin is injected directly into the targeted muscle. The product begins to block nerve signals shortly after the injection.
Action time: although some people feel an improvement after 2 or 3 days, the definitive results are obtained 7 days later.
Duration of effect: the muscles will remain relaxed for approximately 3 to 6 months, before the nerve endings regenerate.

Differences between Botox and other beauty treatments

It is important to differentiate Botox from other injectables such ashyaluronic acid.

  • Botox: relaxes the muscles responsible for expression lines (dynamic wrinkles).
  • Hyaluronic acid: fills in static wrinkles, hydrates the skin and restores lost volume.

These two treatments are often complementary, but they do not work in the same way. Hyaluronic acid is a dermal filler, while botulinum toxin acts on the underlying muscles through a muscle blocking mechanism.

Long-term effects of Botox

Repeated injections of botulinum toxin have long-term benefits. When the muscles are continually relaxed, wrinkles do not form as easily, which can slow down the ageing process of the face in the treated areas. However, it is essential to respect reasonable intervals (4 to 6 months) between injections to avoid the development of tolerance to the toxin.

Safety of botulinum toxin injections

Botulinum toxin injections are considered safe when carried out by an experienced doctor. The most common side effects are minor, such as redness or bruising at the injection site, and generally disappear after a few days.