M. Payne

Is conditioned pain modulation disrupted in sexual assault survivors

 Conditioned Pain Modulation (CPM) -Test stimulus: electric stimulations at an intensity that was individually calibrated for each participant -Conditioning stimulus: painful 10° C cold water Introduction Sexual assault (SA) is defined as any form of sexual contact that occurs without the explicit consent of the recipient and ranges from unwanted touch to rape. SA is associated with increased chronic pain risk and numerous chronic pain conditions. Recent findings from our research group suggest that SA survivors exhibited hyperalgesia and difficulty engaging in descending modulation of spinal nociception (assessed via the nociceptive flexion reflex [NFR]) via emotional processes. To our knowledge, no study has examined the relationship between SA and conditioned pain modulation (CPM; pain inhibits pain). The present study examined the relationship between SA and CPM in a sample of SA survivors and a matched comparison group.

345) Is history of traumatic events associated with nociceptive flexion reflex (NFR) threshold

 Overview, Informed Consent & Eligibility Determination (Health Status Screening) -Two testing sessions were completed on separate days -Testing session and test order were counterbalanced -Informed consent obtained at beginning of first testing session  Life Events Checklist Administered -Self-report measure that indicated the number of traumatic events an individual has experienced in their lifetime  NFR Threshold Testing -Sensors and stimulating electrode applied to the left ankle over the sural nerve -Suprathreshold intensity assessed used during NFR magnitude testing  Heat Pain Threshold Testing Heat probe placed on the left volar forearm Pain threshold was defined as the temperature (in °C) at which point the individual reported they first felt the probe become painful (the average temperature of 4 trials)  Heat Pain Tolerance Testing Heat probe placed on left volar forearm Pain tolerance was defined as the temperature (in °C) at which point the individual reported they could no longer tolerate the pain from the heat (the average temperature of 4 trials) Introduction

348) Are there sex differences in the relationship between pain locus of control and pain sensitivity

individual neurons, with the long-term goal of correlating these observations to patients’ medical history. We have also co-cultured human DRG with non-neuronal human keratinocytes to investigate whether signaling cross-talk and sensitization may occur, especially in cases of chronic itch. We anticipate that these approaches will be very informative of the underlying neurobiology of human neurons and allow for improved translational outcomes.

346) Is resting blood pressure associated with emotional modulation of pain

Procedures These data were taken from a parent study investigating pain processing in Native American individuals Stimulating electrode was applied over the sural nerve of the left ankle  Resting blood pressure (systolic/diastolic) readings were taken before pain testing procedures began Emotional Controls of Nociception was among the experimental pain procedures assessed  Participants received electrocutaneous stimulations while viewing:  Unpleasant Pictures (e.g., injured bodies)  Neutral Pictures (e.g., household objects)  Pleasant Pictures (e.g., people in sexual acts) Introduction Blood pressure (BP) is associated with pain processing and pain modulation. For example, resting BP is associated with the effectiveness of conditioned pain modulation (i.e., pain inhibiting pain). To the best of our knowledge, however, no study has investigated the relationship between BP and the effectiveness of other forms of pain modulation systems. In an effort to expand this literature, the current study will investigate the relationship between the effectiveness of emotional controls of nociception [ECON] and resting blood pressure in healthy pain-free individuals.

(329) Temporal habituation of heat pain? Parameters used for measuring temporal summation primarily lead to decreases in pain ratings

Animal studies have shown that dorsal horn neurons become hyperexcitable (ie, wind-up) in response to a repetitive, constant-intensity, noxious stimulus. Temporal summation of pain (eg, increased pain in response to a repetitive, constant-intensity painful heat pulse) is believed to reflect the psychophysical correlate of wind-up. We examined temporal summation of heat pain (TS-heat) using previously published procedures in 107 healthy, pain-free participants from the community. To assess TS-heat, participants received 5 blocks of 10 heat pulses from a Contact Heat Evoked Potential Stimulator (CHEPs) attached to the volar surface of the left forearm, and the thermode was moved in between blocks. Pulse peak was determined from a preliminary workup that determined the temperature that evoked pain of 45 out of 100. TS-heat was assessed after thermal sensory thresholds, but was randomized with three other pain tests (heat pain threshold/tolerance, electric pain tolerance, pressure pain threshold). Two pulse train parameters were attempted (between-subjects) with the same 3-s ISI: 1) from baseline of 35 C, each pulse reached peak temperature in 0.5-s, held peak for 0.5-s, and returned to baseline in 0.5-s, 2) from baseline of 39 C, each pulse reached peak temperature in 0.5-s, held peak for 0.75-s, and returned to baseline in 0.5-s. Three methods were used to calculate TS-pain: 1) TStrend=mean pain ratings across all 10 pulses, 2) TS10=10 th pain rating minus 1 pain rating, and 3) TSmax=max pain rating of pulses 2-10 minus 1 pain rating. Analyses examined whether train parameter, testing order, or calculation method had an effect on TS-heat. Analyses revealed habituation rather than summation in all cases except when TSmax was employed. Even then, average summation was minimal (change=1.3-2.7 on 100point scale) and non-significant. Results suggest these TS-heat proceduresmay primarily measure habituation processes. Further investigation of the underlying neural mechanisms of TS-heat is warranted.