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PubMed · 14642787

Morphine-induced decrease in mechanical allodynia is mediated by central, but not peripheral, opioid receptors in rats with inflammation.

Shao Li·Zhi-Qi Zhao
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Abstract

The aim of this study was to investigate the mechanism underlying the effect of morphine on allodynia to complete Freund's adjuvant-induced inflammation in rats. Morphine (5 mg/kg, i.v.) markedly inhibited the mechanical stimulation-induced nociceptive reflex of the gastrocnemius muscle in the inflamed hind-limb, and the inhibition was blocked by naloxone (1 mg/kg). Teased fiber recordings were made from the tibial nerve innervating the inflamed hindpaw. Morphine at the same dose did not affect the spontaneous firing rate of A-type fibers, whereas it markedly decreased the spontaneous firing of C-type fibers. The present data suggested that the central, but not peripheral, plasticity triggered by inflammation-induced facilitation of A(beta) fibers plays an important role in morphine-induced alleviation of allodynia, whereas activation of opioid receptor expression on the peripheral terminals of C fibers may contribute to morphine-induced alleviation of persistent pain of inflammation.

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AnimalsInflammationMaleMorphineNerve Fibers, MyelinatedNerve Fibers, UnmyelinatedPain MeasurementPhysical StimulationRatsRats, WistarReceptors, OpioidJournal ArticleResearch Support, Non-U.S. Gov't

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Shao Li, Zhi-Qi Zhao. 2003-11-28. Morphine-induced decrease in mechanical allodynia is mediated by central, but not peripheral, opioid receptors in rats with inflammation.. https://doi.org/10.1016/j.ejphar.2003.09.032

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