The Journal of Pain Summary

Highlight from The Journal of Pain (Volume 20, No. 2, February 2019)

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Pharmacological Modulation of Endogenous Opioid Activity to Attenuate Neuropathic Pain in Rats

Nai-Jiang Liu, Emiliya M. Storman, Alan R. Gintzler; Department of Obstetrics and Gynecology; State University of New York, Downstate Medical Center; Brooklyn, NY.

These authors previously demonstrated that spinal mGluR1 signaling suppresses or facilitates (depending on the stage of estrous cycle) analgesic responsiveness to intrathecal endomorphin 2, a highly μ-opioid receptor (MOR)–selective endogenous opioid. In this study, the authors hypothesized that female rats subjected to spinal nerve ligation, inhibition of spinal estrogen synthesis, or blockade of spinal mERα/mGluR1 would be anti-allodynic during diestrus, whereas during proestrus, the mGluR1 blockade would worsen the mechanical allodynia.

As postulated, following spinal nerve ligation, aromatase inhibition or mERα/mGluR1 blockade during diestrus lessened mechanical allodynia. This indicated that rats are more susceptible to develop greater surgically induced mechanical allodynia during diestrus than during proestrus. These results provide a foundation for developing drugs that harness endogenous opioid antinociception for chronic pain relief.

This research could help lessen the need for exogenous opioids and have an impact on prescription opioid abuse.