Physiological Mechanisms of Acupuncture

Neurohormonal Theory – Transmission of pain can be adjusted or modulated along various pain pathways at many levels in the brain. These pathways include the Periaqueductal Gray, Thalamus and the feedback pathways from the Cerebral cortex to the thalamus.

Each one of these structures of the brain are responsible for processing different aspects of the pain like emotional pain, perception of the pain, recognition of the harm caused by the pain, localizing the origin of the pain, etc.

Blockage of the pain at these locations of the brain is mediated by the neurohormones especially the ones which bind to the opioid receptors which are the pain blockade sites.

Relief of pain by administering morphine drug or the exogenous opioid acts on the same opioid receptor as do the endorphins and the endogenous opioids. These are produced and released by the brain.

Some other studies stipulate that the acupuncture procedure stimulates the discharge of ‘natural-endorphins’ in our brain. This fact can be proved conclusively by blocking the action of endorphins or morphine. This is done by using a drug called naloxone.

By administering naloxone, the patient begins to feel the pain again. This is because naloxone reverses the analgesic effects of morphine. Similarly, the pain-relieving effect produced by acupuncture is reversed by administering naloxone. This causes the patient to start feeling the pain again.

This proves that acupuncture causes the natural release of endorphins by the brain which can be reversed by naloxone. This analgesic effect is found to last for more than an hour after acupuncture procedure. This can be shown by recording the neural activity directly in the thalamus or the pain processing site of the monkey’s brain.

The overlap between the nervous system and the acupuncture points is also large. The sites where the acupuncture induced analgesia acts is confirmed to be the thalamus which is where the emotional pain and suffering is processed.

This is done using the non invasive functional magnetic resonance imaging or the fMRI, the positron emission tomography or the PET, brain imagine techniques and also through the feedback pathway from the cerebral cortex.

The cerebral cortex is where the cognitive feedback signal to the thalamus distinguishes whether the pain is noxious or painful or innocuous or not harmful. This is done using the electrophysiological recording of the nerve impulses of the neurons in the cortex. This shows inhibitory action during the acupuncture procedure when stimulus was applied.

Recent research on acupuncture has also proven that acupuncture increases the nitric oxide levels in the areas that have been treated. Consequently, there is an increase in the blood circulation in that area.