Temporal and Spatial Changes of μ-Opioid Receptors in the Brain, Spinal Cord and Dorsal Root Ganglion in a Rat Lumbar Disc Herniation Model
Abstract
Controlled, interventional, animal study. To investigate the spatial and temporal changes of μ-opioid receptor (MOR) expression in a rat lumbar disc herniation (LDH) model. MORs widely express in the peripheral and central nervous systems, and opioid drugs produce an analgesic effect through their activation. However, the efficacy of opioid drugs is sometimes inadequate in several pathological conditions of pain. MORs in the brain as well as the spinal cord (SC) and dorsal root ganglion (DRG) are thought to be associated with pain-related behavior, but the underlying mechanisms are not completely understood. In all, 91 adult female Sprague-Dawley rats were used. Autologous nucleus pulposus (NP) was applied onto the left L5 DRG in the NP group rats. Rats were divided into two surgical groups, the NP and the sham group. The von Frey test of left hind paw was performed before surgery, and 2, 7, 14, 21 and 28 days after surgery. Immunohistochemistry and immunoblotting in the DRG, SC, Caudate putamen, nucleus accumbens (NAc) and periaqueductal grey matter were performed before surgery, and 2, 7, 14, 21 and 28 days after surgery. The thresholds in the NP group were significantly lower than those in the sham group from day 2 onwards. ...Continue Reading
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The inflammatory effect of nucleus pulposus. A possible element in the pathogenesis of low-back pain
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