Physiology and Pharmacology

en Morphine-induced analgesic tolerance is associated with alteration of protein kinase Cγ and transient receptor potential vanilloid type 1 genes expression in rat lumbosacral cord and midbrain Pain and addiction Neurophysiology/Pharmacology Experimental research article Experimental research article Introduction: Transient receptor potential vanilloid type 1 (TRPV1) and protein kinase Cγ (PKCγ) are involved in sensitization/desensitization to noxious stimuli. We aimed to examine the gene expression levels of TRPV1 and PKCγ in rat lumbosacral cord and midbrain on days 1, 4 and 8 of induction of morphine analgesic tolerance. Methods: Two groups of male Wistar rats received twice daily saline (1 ml/kg) or morphine (10 mg/kg) for eight days and were monitored for analgesic tolerance with a hotplate test on days 1, 4 and 8 of the injections. Six independent groups in three sets were also treated with saline or morphine, decapitated on days 1, 4 or 8 of the schedule, respectively and their lumbosacral cord and midbrain were dissected. Results: The result of the hotplate test revealed induction of analgesic tolerance on days 4 and 8 of morphine injections. The TRPV1 gene expression in the lumbosacral cord was significantly increased only on day 4 of morphine injections, but the PKCγ gene expression remained with no significant changes on days 1, 4 and 8. In the midbrain, the TRPV1 gene expression was significantly increased only on day 1; however, the PKCγ gene expression was significantly increased on days 4 and 8 of morphine injections. Conclusion: It can be concluded that the TRPV1 gene expression changes in the lumbosacral cord and midbrain is associated with early phase of morphine-induced analgesic tolerance but the PKCγ gene expression is altered only in midbrain at the later phase of process. Morphine, Analgesic tolerance, Gene expression, Spinal cord, Midbrain, TRPV1, PKCγ 147 156 http://ppj.phypha.ir/browse.php?a_code=A-10-916-1&slc_lang=en&sid=1 Shamseddin Ahmadi sh.ahmadi@uok.ac.ir 3200319475328460016684 3200319475328460016684 Yes Department of Biological Science and Biotechnology, Faculty of Science, University of Kurdistan, Sanandaj, Iran Neda Parvini n.parvini@uok.ac.ir 3200319475328460016685 3200319475328460016685 No Department of Biological Science and Biotechnology, Faculty of Science, University of Kurdistan, Sanandaj, Iran