Abstract Introduction: Matrix metalloproteinase 2 is one of the inflammatory mediators that is involved in nociceptive processing and its production is regulated by many inflammatory factors such as nitric oxide. We studied the role of MMP-2 on the analgesic effects of nNOS inhibitor. Methods: Considering that nitric oxide has many roles in pain processing, we studied the CSF levels of MMP-2 after hind paw formalin injection (50µl, 2.5%) and neuronal nitric oxide synthase inhibition intrathecally. We also studied the effect of MMP-2 inhibitor on pain behavior and its role on analgesic effect of neuronal nitric oxide synthase (nNOS) inhibitor. Results: Rats that received MMP-2 inhibitor (30mM) showed severe responses to the formalin injection. Pain was reduced after nNOS inhibition. Prior to nNOS inhibitor injection, MMP-2 inhibition reduced the analgesic effects of nNOS inhibitor. Immunological study showed that MMP-2 increased in rats that received nNOS inhibitor. Conclusion: These data suggest the possible roles for MMP-2 in analgesic effect of nNOS inhibitor.

Keywords: matrix metalloproteinase, nitric oxide, formalin test.

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