Journal of pharmacological sciences
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We evaluated the effect of buprenorphine, a mixed agonist for μ-opioid receptors and nociceptin/orphanin FQ peptide (NOP) receptors, in neuropathic rats, using the paw pressure test. Buprenorphine, administered i.p. at 50, but not 20, μg/kg, exhibited naloxone-reversible analgesic activity in naïve rats. ⋯ Intrathecal injection of [N-Phe(1)]nociceptin(1-13)NH2, a NOP-receptor antagonist, reversed the effect of buprenorphine in neuropathic rats, but not in naïve rats. Together, buprenorphine suppresses neuropathic hyperalgesia by activating NOP and opioid receptors, suggesting its therapeutic usefulness in treatment of neuropathic pain.
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Chronic pain refractory to non-steroidal anti-inflammatory drugs (NSAIDs) is a major problem and drugs for such pain are needed. Many studies suggest that transient receptor potential vanilloid type 1 (TRPV1) is associated with NSAID-refractory chronic pain. Therefore, we investigated the involvement of TRPV1 in NSAID-refractory chronic pain using experimental models for NSAID-refractory chronic pain reflecting severe arthritic and postherpetic pain. ⋯ JTS-653 did not affect the nociception of noxious thermal and mechanical stimuli and motor coordination in normal rats. These findings demonstrate the TRPV1 involvement in NSAID-refractory chronic pain reflecting severe arthritic and postherpetic pain. TRPV1 antagonists would be useful for the treatment of NSAID-refractory chronic pain.
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Neuropathic pain is a highly debilitating chronic pain state that is a consequence of nerve injury or of diseases such as diabetes, cancer, infection, autoimmune disease, or trauma. Neuropathic pain is often resistant to currently available analgesics. There is a rapidly growing body of evidence indicating that signalings from spinal microglia play crucial roles in the pathogenesis of neuropathic pain. ⋯ Inhibiting function or expression of these microglial molecules strongly suppresses pain hypersensitivity to innocuous mechanical stimuli (tactile allodynia), a hallmark symptom of neuropathic pain. A recent study also reveals that the transcription factor IRF8 (interferon regulatory factor 8) is a critical regulator of the nerve injury-induced gene expression in microglia. The present review article highlights the recent advances in our understanding of spinal microglia in neuropathic pain.
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Individual differences in the sensitivity to fentanyl, a widely used opioid analgesic, can hamper effective pain treatment. The adrenergic system is reportedly involved in the mechanisms of pain and analgesia. Here, we focused on one of the adrenergic receptor genes, ADRB1, and analyzed the influence of single-nucleotide polymorphisms (SNPs) in the ADRB1 gene on individual differences in pain and analgesic sensitivity. ⋯ The analgesic effect was significantly less in females who carried the G-allele of the G1165C SNP than the females who did not carry the G-allele. The haplotype analysis revealed a significant decrease in 24-h postoperative fentanyl use in female 145A/1165C haplotype carriers. These results suggest that SNPs in the ADRB1 gene are associated with individual differences in pain and analgesic sensitivity, and analyzing these SNPs may promote personalized pain treatment in the future.
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Microglial-mediated neuroinflammation has recently been implicated as one of the important mechanisms responsible for the progression of neurodegenerative diseases. Activated microglia cells produce various neurotoxic factors that are harmful to neurons. Therefore, suppression of the inflammatory response elicited by activated microglia is considered a potential therapeutic target for neurodegenerative diseases. ⋯ CD-101 significantly inhibited the production of inflammatory markers such as nitric oxide, cyclooxygenase-2, and pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, and interleukin-6. The anti-neuroinflammatory effect of this novel cannabinoid derivative occurred by inhibiting p38MAPK phosphorylation and by decreasing nuclear translocation of p65 subunit of nuclear factor kappa-B in LPS-stimulated BV-2 microglial cells. These results suggest that the use of the cannabinoid derivative CD-101 might be a potential therapeutic target against neuroinflammatory disorders.