“How does acupuncture work?”

This is one of the most common questions I get. And the answer can be complicated. There is a Traditional Chinese Medicine explanation which involves the concept of “Qi” (the life force energy”). And in recent years, there is more and more western scientific evidence that validates the effectiveness of acupuncture.

It’s really fascinating stuff, actually.

I am in awe of all the intricacies that make up our body to make everything function the way it does.

For example, “How does acupuncture block pain?”

The pain receptors in the body are called nociceptors, they are nerve cell endings that respond to signals of tissue damage and initiate the process of pain. The information is relayed by 2 types of pain fibers to the spinal cord.

1. Type A Delta Fiber: This is the smaller nerve fiber that has a protective covering called “myelin” which increases the speed of the information transmitted

2. Type C Fiber: does not have myelin and transmits information slower

Once the pain signal reaches the spinal cord, it passes through different areas within the spinal cord by a pathway called Tract of Lissauer.

Then the signal passes from one side of the spinal cord to the other side and then onward to the brain area. A lot of the pain sensation is processed in the brainstem (the lower part of the brain), some reaches the thalamus, hypothalamus, pituitary and the mid brain area, and still fewer go on to the higher center of the cerebral cortex area.

Brainstem = The lower part of the brain that connects with the spinal cord

Thalamus = A small structure within the brain between the lower brainstem and the larger cerebral part of the higher brain. It is near the center of the whole brain.

Hypothalamus = Just below the thalamus, this controls certain metabolic processes and coordinates the Autonomic Nervous System.

Pituitary = A pea sized gland responsible for secretions of many important hormones in the body

Basically – After a pain signal is initiated, it is relayed by pain fibers to the spinal cord which then carries the information to various parts of the brain where the sensation of pain is processed.

This is like a roadmap for pain: Imagine the process of a pain sensation is like a person going to the park by driving a car. The person represents the trigger for pain, and the car is the vehicle that carries the pain signal, and the park is the brain that processes the pain. The person would get into the car, and drive to the park.

Person: Signal for pain

Car: Nerve fibers and spinal cord that transport the signal for pain

Park: The brain

There are 2 ways to get to the park, one is through local streets which is slower, and the other is through a highway which is faster. The local streets represent the slower C fiber and the highway is like the A delta fiber. Either way, the person would arrive at the park. Once there, there are different areas where the person can choose to park the car – this is like the different areas of the brain where pain sensation can be received. And finally the person will get out of the car and arrive at the park, which represents the pain sensation being finally processed at the brain.

In this example, we can stop the person from getting into the park by a few places along the way.

1) Preventing the person from getting in the car ( = Preventing the signal from getting to the spinal cord)
2) Block the route along the way so the car cannot get to the park ( = Preventing the signal from getting to the brain)
3) Close the parking area so the car cannot park ( = Preventing the signal from being processed in different brain areas)

When an acupuncture point is stimulated, local nerve fibers are activated by the sensory input (pressure, touch, or vibration of the needling). These fibers travel through the same pathway as pain signal and arrive at spinal cord, brainstem, or the midbrain area. These centers then send out neurotransmitters to block pain signals.

In our example, we can think of neurotransmitters as police that are sent out to block the different areas so the person cannot get to the park.

The most important neurotransmitters are:
1. The Endorphins (most commonly known as the “feel-good” hormones). These hormones respond to the opioid receptors in the body.

  • β-Endorphins
  • Enkephalins
  • Dynorphin

2. The Monoamines

  • Serotonin
  • Catecholamines

These neurotransmitters play important parts in the perception of pain and their effects and actions can be measured following acupuncture treatment, giving evidence that acupuncture treatment helps with reducing pain sensation.

Current research is using MRI to highlight different areas of the nervous system and how they are responding when acupuncture treatments are performed.

Another theory of why acupuncture may block pain perception is called the Gate Control Theory. The region in the spinal cord responsible for relaying pain messages to the brain is called the substantial gelatinosa. Sensory sensation from acupuncture needles travel faster via the myelinated nerves (A-Delta fibers) and this information arrives at substantial gelatinous faster than the pain impulses traveling on the slower acting nerve fibers (C fibers) and it closes the “gate” that allow more pain signals to get through.

This is kind of like the substantial gelatinous as a place of party and only 100 people are invited, after the first 100 guests arrive, the gate is closed and not allowing more people to get through. Whoever gets there faster can get through the gate. Sensory information from acupuncture (non-painful impulses) can travel faster than the pain impulses, thus get to the processing center in the spinal cord faster, closing the gate and thus blocking pain signals.

The Local Effects of Acupuncture

And what exactly happens at the site locally when acupuncture needles are inserted?

Acupuncture points are located at areas that we call neural vascular bundles – that means this is a special area underneath the skin that has free nerve endings, an artery and vein, a lymphatic vessel, and mast cells.

A mast cell is a special type of cell in the body that releases a chemical called histamine – this is an important step in triggering the immune system to respond during inflammation.

When a needle is placed in the acupuncture point, there is a small tissue trauma induced by the needle. When this happens, it stimulates a cascade of reaction in the body (the coagulation cascade and the complement cascade) and a variety of compounds are released (inflammatory mediators such as bradykinin, prostaglandins, plasminogen). The micro trauma also causes mast cells to release histamine, which, in turn, liberates nitric oxide (NO) that helps to mitigate pain.

The resulting action from these compounds is relief of pain locally due to increased blood flow to the area and decreased muscle spasm.

Think of the acupuncture needling as “waking up the body” in areas where the injury or pain may be chronic or low grade enough that the body allows it to continue without active efforts to repair or reduce inflammation. This happens because the body is programmed to respond to areas with more urgent needs, and chronic conditions may be “ignored” by the body over time.

Acupuncture helps to heighten the awareness of the body to tend to its injury.

In reality, there are so many different ways why acupuncture might work. It is likely they all play a part in making this an effective treatment.

We are now able to use modern science to explain the effects of acupuncture. It is fascinating to me that this form of medicine has been practiced for thousands of years and we might just be beginning to understand it “scientifically”. I can barely scratch the surface here as pain perception in the body is an extremely complicated process. Of course different animals can experience and be affected by acupuncture differently as each body has its own unique make up and the way it responds based on its genetics, receptor differences, and health conditions. But there is no denying the measurable effects acupuncture has with modulating pain response.

If you think your pet has a painful condition, consider acupuncture treatment! It is a safe, effective way to help with pain.