Spinal microglia are dispensable for the development of opioid-induced hyperalgesia
Adverse side effects of chronic opioid use, including analgesic tolerance, opioid-induced hyperalgesia, and addiction, are serious clinical challenges for pain management and opioid deprescribing. Microglia have been implicated in the development of these adverse effects, but the extent to which opioids alter microglia and the mechanisms behind opioid effects on microglia are poorly understood.…
Chronic opioid use can lead to undesirable side effects, such as increased pain sensitivity, worsening of pain symptoms, and dependence. While research suggests that microglia, a type of immune cell in the brain and spinal cord, may contribute to these issues, the exact relationship between opioids and microglia remains unclear.
To investigate this, scientists examined the spinal microglia from mice that had been exposed to opioids versus those that had not. They observed that while the microglia from opioid-exposed mice showed the same physical characteristics as those from saline-treated mice, their molecular activity was only slightly different. Notably, the scientists found that giving opioids only to certain parts of the body, rather than throughout the whole body, could still cause heightened pain and physical changes in the microglia.
However, when they completely removed microglia in mice that normally have them, the mice still experienced opioid-induced pain and withdrawal symptoms. These findings indicate that microglia may not play a crucial role in the development of opioid-related pain issues.
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