by Madhumathi Palaniappan on  January 18, 2017 at 5:28 PM Health Watch
  • Opioid drugs are pain relieving drugs that act by blocking the signals in the brain.
  • New signaling pathway involves activation of opioid receptors in the immune cells.
  • Immune cells were found to increase the analgesic effect of opioid drugs.

Analgesic or pain relieving effect of opioids are not only mediated by the opioid receptors in the brain but can also be activated through the opioid receptors in the immune cells, finds a research study from Charité - Universitätsmedizin Berlin.

The study findings which show pain reduction in mice due to opioid receptors in the immune cells were published in the journal Brain, Behavior and Immunity.
New Signaling Pathway For Opioid Drugs

Opioid drugs like morphine is a standard treatment for pain. These drugs were found to reduce the pain by decreasing the sensory neurons in the brain.

Since most of the pain conditions were often linked with the peripheral nerve tissues that are infiltrated with the immune cells.

Prof. Dr. Halina Machelska, researcher at the Department of Anesthesiology and Critical Care Medicine at the Charite-Campus Benjamin Franklin, said, "This prompted us to ask whether opioids could also inhibit pain by acting on immune cells."

"We hypothesized that opioids act at opioid receptors on immune cells and release endogenous opioid peptides such as endorphins, enkephalins and dynorphins. The secreted opioid peptides would then activate neuronal opioid receptors and reduce pain."

The research team led by professor Machelska found that three different opioid receptor agonist drugs in animal model was found to reduce pain.

The findings depicted that animals with reduced number of immune cells experienced much weaker analgesic effect. And when the immune cells were increased the analgesic effect was restored.

Professor, Machelska, said, "We were able to show that opioid agonists activate opioid receptors on immune cells, which triggered the release of endogenous painkillers (opioid peptides) and produced analgesia in a mouse model of neuropathic pain."

"This led us to conclude that opioids can exert enhanced analgesia when they act directly in painful tissue - providing that this tissue is inflamed and contain immune cells." she added.

The study findings were found to be relevant for most of the pain conditions like cancer pain, arthritis, nerve damage that were associated with an immune response.

Opioids acting directly within the peripheral inflammed tissue will not produce undesirable effects like nausea, breathing difficulties and addiction.

The study findings were found to help in providing new opioids that exert analgesia which is infiltrated by the immune cells.

Opioid Drugs
Opioid drugs are powerful pain relieving drugs that are prescribed for managing both acute and chronic pain. These drugs act mainly by blocking the pain signals in the brain.

Examples of opioid painkillers include: morphine, methadone, hydrocodone and oxycodone.

  1. What drugs are opioids? - (
  2. Safe Use, Storage, and Disposal of Opioid Drugs - (

Source: Medindia

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