immune and opioid system interaction in pain modulation

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 be in pain modulation. purpose of this study was to review the effect of immune and opioid systems on pain modulation. increasing demand for mitigating inflammatory pain has led to the introduction of the effect of immune and opioid system interaction in pain modulation. we reviewed 61 related articles from 1991 to 2016. 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. in addition, there is relationship 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 anti-nociceptive and anti-inflammatory effects. 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.