Acupuncture for Pain Management

Linda M. Rapson, MD, CAFCI; Robert Banner, MD, CCFP, FRCP(C)

Disclosures

Geriatrics and Aging. 2008;11(2):93-97. 

In This Article

Neurophysiology of Acupuncture Analgesia

By 1987, through a series of animal experiments conducted by his team and others, Pomeranz had developed a theory of acupuncture analgesia using electroacupuncture (EA) that begins with needle activation of A delta and C afferent fibres in muscle sending signals to the spinal cord, where dynorphin and enkephalins are released (see Figure 1). The afferent pathways continue to the midbrain, triggering excitatory and inhibitory mediators in the spinal cord. The ensuing release of neurotransmitters serotonin and norepinephrine onto the spinal cord leads to pain transmission being inhibited both pre- and postsynaptically in the spinothalamic tract. Finally, these signals reach the hypothalamus and pituitary, triggering the release of adrenocorticotropic hormones and beta-endorphin. These effects are dependent on the rate of stimulation: low-frequency stimulation at 4 Hz releases enkephalin and beta-endorphin, and high-frequency stimulation at 100 Hz releases serotonin and norepinephrine.[2,3]

Neurophysiology of Acupuncture Analgesia

Pomeranz's theory has been confirmed and refined by experiments in his laboratory and by other investigators.[4,5] In recent years, basic research has included positron emission tomography, single-photon emission computed tomography, and functional magnetic resonance imaging studies to observe the effects on the brain of acupuncture needling. The effects are widespread and open to interpretation, but there is evidence that the limbic system plays a significant role in acupuncture-induced analgesia. A study comparing true and sham EA at a single acupuncture point used for analgesia showed that both activated central pain pathway regions but only true EA activated the primary somatosensory cortex, the motor cortex, and the hypothalamus while deactivating the rostral segment of the anterior cingulate cortex. This implies that EA stimulation modulates the hypothalamus-limbic system.[6,7,8,9]

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