Endorphins and Pain

  • L. Terenius


Pain is the behavioural response to external or internal noxious stimuli. Clinical pain is very different from experimental pain and it is proposed that pain forms a hierarchy starting with activation of sensory fibres or internal clues and terminating with processing in the CNS at various levels. It is the affective component of pain which is influenced by morphine, and not the sensory thresholds. Endorphins should be expected to have an action similar to morphine, and experimental evidence is in keeping with this contention.

Three different areas relating to endorphins and pain are reviewed. Firstly, evidence is given that endorphins may be responsible for adaptation to pain, either congenital or acquired, as well as to diurnal changes in pain sensitivity. It is possible, in fact, that endorphins have a more general role in sensory adaptation. Secondly, some evidence suggests that endorphins are released in acute trauma and may play a protective role, for instance in parturition. Finally, endorphins seem to be involved in chronic pain. Patients with chronic neurogenic pain frequently show low levels of endorphins in their cerebrospinal fluid. These low levels may be raised by acupuncture with pain relief as a result. The relief of pain is reversed by the narcotic antagonist naloxone. These observations converge on one point, that endorphins play an important modulatory role and inadequate endorphin activity leads to pathologic changes.


Chronic Pain Opioid Receptor Pain Threshold Trigeminal Neuralgia Pain Sensitivity 
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Copyright information

© MTP Press Limited 1980

Authors and Affiliations

  • L. Terenius
    • 1
  1. 1.Institutionen För Farmakologi, Biomedicinska CentrumUppsala UniversitetsUppsalaSweden

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