title: Endogenous inhibition of pain and spinal nociception in women with premenstrual dysphoric disorder.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Shreela
authors.initials: S
authors.lastname: Palit
authors.affiliation: Department of Community Dentistry and Behavioral Science, Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Bartley
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Bethany L
authors.initials: BL
authors.lastname: Kuhn
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Kara L
authors.initials: KL
authors.lastname: Kerr
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: DelVentura
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Ellen L
authors.initials: EL
authors.lastname: Terry
authors.affiliation: Department of Psychology, University of Tulsa, Tulsa, OK, USA.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Rhudy
keywords: conditioned pain modulation; menstrual cycle; nociception; pain; premenstrual dysphoric disorder