Immune and Opioid system interaction in pain modulation

Background: Inflammatory pain is caused by direct stimulation of nociceptors with the release of inflammatory mediators. Several studies about the roles of immune and opioid systems in the pain process have suggested that their crosstalk may have effective in pain modulation. Accordingly, the purpose of this study was review the effect of immune and opioid systems on pain modulation.Evidence acquisition: The increasing demand for mitigating inflammatory pain has led to the introduction of the effect of immune and opioid system interaction in pain modulation. Our literature reviewed 61 articles from 1991 to 2016.Results: In this study, we reviewed most of the existing papers on the role of opioid system in pain modulation especially with a focus of the immune system efficacy. Our review suggested that there is a close correlation between the expression of cytokines and opioid receptors and in the process of inflammatory pain where immune cells have a notable effect on the expression of cytokines and opioid receptors. In the process of inflammation, different types of immune cells constitute a major source of opioid peptides. The endogenous opioids could modulate either their own secretion or secretion of other cytokines. They have also antinociceptive and antiinflammatory effects.Conclusion: Exacerbation of immune and opioid system reactions via correlation between cytokines and opioid peptides in the context of inflammatory pain arises the possibility of the role of interaction of these two important systems in the pain process. Keywords: inflammatory pain, opioids, immune system, cytokines, hyperalgesia