Ethnic differences in effects of opioid blockade and behavioral analgesia on pain

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DESCRIPTION (provided by applicant): Persistent pain is a public health epidemic producing enormous economic costs and profound human suffering. Considerable evidence indicates that, compared to non-Hispanic whites, African Americans are at substantially higher risk for experiencing severe, disabling, clinical pain states (both acute and chronic), and are more sensitive to a broad variety of noxious stimuli delivered in laboratory studies. While major advances in many areas of pain research have been made in recent years, explanations for the ethnic differences observed in responses to pain remain poorly understood. In light of the increasing diversity of the US population, illuminating the mechanisms that underlie ethnic differences in pain perception has become a topic of substantial scientific and clinical importance, and extending this line of research should eventually aid in reducing pain-related disparities in health. Therefore, the purpose of this proposal is to elucidate the role of the endogenous opioid system in contributing to ethnic differences in the experience of pain. Specifically, this project will investigate responses to capsaicin-induced pain, the analgesic effects produced by a cognitive-behavioral pain-coping strategy (i.e., distraction), and whether blockade of the endogenous opioid system affects ethnic differences in pain and analgesia in a sample of 52 medically healthy individuals (50% African American, 50% non-Hispanic White; 50% Women in each ethnic group). The aims of the current proposal are to: 1) evaluate ethnic differences in the contribution of endogenous opioids in pain perception of capsaicin induced pain; 2) characterize differences in the effectiveness of distraction analgesia during capsaicin-induced pain among African Americans and non-Hispanic whites; 3) determine whether ethnic differences in the effectiveness of a distraction analgesia task are influenced by endogenous opioids; and 4) whether psychological factors influence ethnic differences in pain sensitivity, response to the behavioral analgesic manipulation (distraction), or opioid receptor blockade. Subjects will participate in four experimental sessions (in a randomized order); in each of these they will be exposed to capsaicin "alone" or during a distraction task, and will undergo double-blinded administration of either naloxone, an opioid antagonist, or saline. Collectively, the findings from this proposed study will provide valuable insight into the mechanisms underlying ethnic differences in pain perception, and will provide the most definitive answer to date regarding the contribution of endogenous opioids to ethnic differences in pain, Identifying the neurobiological pathways that contribute to ethnic differences in the experience of pain will eventually provide targets for intervention to reduce the scope and impact of pain among African-Americans.