Non-Hispanic black adults exhibit greater μ-selective agonist binding potential (BPND; [11C]carfentanil) in several different brain regions compared with non-Hispanic white adults, suggesting μ-opioid receptor (MOR) function may play a role in ethnic differences in pain perception. This is according to a study in PAIN.
Previous studies have established ethnic differences in pain perception; however, the underlying mechanism for these outcomes has not been well established. In this study, investigators used μ-opioid imaging outcomes gathered from high-resolution research tomograph PET scanning to examine differences in BPND; [11C]carfentanil among healthy adults identifying as non-Hispanic black and non-Hispanic white (n=54). Participants were matched for age, sex, education, and income. During a PET imaging session, researchers applied either a capsaicin or control cream to each participant’s arms and measured pain ratings. Perceived racial discrimination and pain sensitivity were assessed and compared between groups.
Compared with non-Hispanic white individuals, people who identified as non-Hispanic black reported a higher rate of perceived racial discrimination (P <.001). The researchers found a significant ethnicity-condition interaction effect for pain sensitivity in an analysis that adjusted for racial discrimination total scores and participants’ reported sex (P =.013).
Participants who self-reported as being non-Hispanic black ethnicity had significantly greater BPND; [11C]carfentanil in bilateral ventral striata (left: F1,52=16.38, P <.001; right: F1,52=21.76, P <.001 left: F1,52=17.3, P <.001; right: F1,52=14.17, P <.001), bilateral subgenual anterior cingulate cortex (left: F1,52=10.4, P =.002; right: F1,52=12.91, P =.001), and right insula (F1,52=11.0, P =.002). Significant correlations remained after controlling for participants’ perceived discrimination and reported sex.
Limitations of the study include the cross-sectional nature of the data and the inclusion of a small number of healthy adults without pain.
The researchers suggest their findings “have implications for endogenous opioid binding as a biological mechanism of ethnic pain disparities within a biopsychosocial framework.” These findings, if replicated, may provide a means for reducing ethnic disparities in pain management.
Letzen JE, Mun CJ, Kuwabara H, et al. Ethnic disparities in pain processing among healthy adults: μ-opioid receptor binding potential as a putative mechanism [published online November 20, 2019]. PAIN. doi: 10.1097/j.pain.0000000000001759