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Jamie L Rhudy,1 Randolph C Arnau,2 Felicitas A Huber,1 Edward W Lannon,1 Bethany L Kuhn,1 Shreela Palit,1 Michael F Payne,1,3 Cassandra A Sturycz,1 Natalie Hellman,1 Yvette M Guereca,1 Tyler A Toledo,1 Joanna O Shadlow1 1The University of Tulsa, Department of Psychology, Tulsa, OK, USA; 2University of Southern Mississippi, Department of Psychology, Hattiesburg, MS, USA; 3Department of Pediatrics, Division of Behavioral Medicine and Clinical Psychology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USACorrespondence: Jamie L RhudyThe University of Tulsa, Department of Psychology, Tulsa, OK, USATel +1918 631-2839Fax +1918 631-2833Email jamie-rhudy@utulsa.eduIntroduction: Native Americans (NAs) have a higher prevalence of chronic pain than other US racial/ethnic groups, but the mechanisms contributing to this pain disparity are under-researched. Pain catastrophizing is oneof the most important psychosocial predictors of negative pain outcomes, and the Pain Catastrophizing Scale (PCS) has been established as a reliable and valid measure of the pain catastrophizing construct. However, before the PCS can be used to study pain risk in NAs, it is prudent to first determine whether the established 3-factor structure of the PCS also holds true for NAs.Methods: The current study examined the measurement (configural, metric, and scalar) invariance of the PCS in a healthy, pain-free sample of 138 NA and 144 non-Hispanic white (NHW) participants.Results: Results suggest that the previously established 3-factor solution fits for both groups (configural invariance) and that the factor loadings were equivalent across groups (metric invariance). Scalar invariance was also established, except for 1 minor scalar difference in a single threshold for item 3 (suggesting NHWs were more likely to respond with a 4 on that item than NAs).Discussion: Results provide additional evidence for the psychometric properties of the PCS and suggest it can be used to study pain catastrophizing in healthy, pain-free NA samples.Keywords: confirmatory factor analysis, pain catastrophizing, Native Americans, pain, ethnic differences, pain coping

Ellen L Terry, Yvette M Güereca, Satin L Martin, Jamie L RhudyDepartment of Psychology, The University of Tulsa, Tulsa, OK, USA Objectives: Prior research has shown a relationship between blood glucose levels and some forms of self-regulation (eg, executive function), with low blood glucose levels associated with impaired self-regulation. Further, engagement in self-regulation tasks depletes blood glucose. Given these relationships, the present study examined whether blood glucose is associated with another form of self-regulation, ie, descending pain modulatory processes. Methods: Forty-seven (32 female) pain-free participants were recruited and completed testing. Blood glucose was measured from finger sticks and a digital meter before and after experimental pain tests. Pain tests included the nociceptive flexion reflex (NFR) threshold to assess descending modulation of spinal nociception, but also electric pain threshold to assess perceptual pain detection. The Stroop color word naming test was also assessed before and after pain testing to examine changes in executive function. Results: Results indicated that mean blood glucose levels decreased after pain testing, but Stroop performance did not significantly change. Importantly, changes in blood glucose were correlated with NFR threshold, such that decreases in blood glucose were associated with lower NFR thresholds (reduced descending inhibition). Changes in blood glucose were unrelated to pain threshold or executive function. Conclusion: This study suggests that glucose depletion may impair performance of descending inhibitory processes, without impacting the perceptual detection of pain (pain threshold). Although findings need to be replicated, maintaining adequate glucose levels may be necessary to support inhibition of spinal nociception. Keywords: pain, nociception, glucose, descending modulation, executive function&nbsp

Shreela Palit,1 Emily J Bartley,2 Bethany L Kuhn,1 Kara L Kerr,1 Jennifer L DelVentura,1 Ellen L Terry,1 Jamie L Rhudy1 1Department of Psychology, University of Tulsa, Tulsa, OK, USA; 2Department of Community Dentistry and Behavioral Science, Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA Purpose: Premenstrual dysphoric disorder (PMDD) is characterized by severe affective and physical symptoms, such as increased pain, during the late-luteal phase of the menstrual cycle. The mechanisms underlying hyperalgesia in women with PMDD have yet to be identified, and supraspinal pain modulation has yet to be examined in this population. The present study assessed endogenous pain inhibitory processing by examining conditioned pain modulation (CPM, a painful conditioning stimulus inhibiting pain evoked by a test stimulus at a distal body site) of pain and the nociceptive flexion reflex (NFR, a spinally-mediated withdrawal reflex) during the mid-follicular, ovulatory, and late-luteal phases of the menstrual cycle. Methods: Participants were regularly-cycling women (14 without PMDD; 14 with PMDD). CPM was assessed by delivering electrocutaneous test stimuli to the sural nerve before, during, and after a painful conditioning ischemia task. Participants rated their pain to electrocutaneous stimuli, and NFR magnitudes were measured. A linear mixed model analysis was used to assess the influence of group and menstrual phase on CPM. Results: Compared with controls, women with PMDD experienced greater pain during the late-luteal phase and enhanced spinal nociception during the ovulation phase, both of which were independent of CPM. Both groups showed CPM inhibition of pain that did not differ by menstrual phase. Only women with PMDD evidenced CPM inhibition of NFR. Conclusion: Endogenous modulation of pain and spinal nociception is not disrupted in women with PMDD. Additionally, greater NFR magnitudes during ovulation in PMDD may be due to tonically-engaged descending mechanisms that facilitate spinal nociception, leading to enhanced pain during the premenstrual phase. Keywords: premenstrual dysphoric disorder, menstrual cycle, pain, conditioned pain modulation, nociception