Fibromyalgia syndrome (FMS), temporomandibular disorders (TMD), and irritable bowel syndrome (IBS) are chronic pain disorders in which sufficient physical findings are often lacking. Despite differences in clinical pain distribution, a number of studies have reported increased pain sensitivity at sites distant from the clinical pain for both TMD 7-10 and IBS. 5,11-16 It is thought that generalized hypersensitivtiy to painful stimuli is associated with increased CNS up-regulation 2,6,17 ; but, it remains difficult to draw conclusions about similarities and differences across these pain conditions. A few studies have also reported the segmental distribution of pain with greater sensitivity in regions associated with clinical pain (IBS) while comparisons across the segmental axis for other conditions (TMD, FMS) are less established. The purpose of the present study was to map the relative degree of sensitization along the segmental axis and to determine the effect of experimental nociceptive inputs on sensitization with methodology that controls for differences in baseline sensitivity between subjects and groups. The finding that the stimulus temperatures required for eliciting the predetermined pain intensity level were significantly lower (i.e., the sensitivity was higher) in the disease groups than in the control group). Our finding of segmental differences in pain sensitivity associated with the distribution of clinical pain for both TMD and IBS. Our data indicated that the calf was the most sensitive to thermal stimuli, followed by the forearm, and lastly the cheek. We also used a testing protocol that allowed us to continuously test the sensitivity of persons with chronic pain while clamping their elicited pain at a constant intensity. Comparison of Heat Pain Sensitivity in Patients C. D. King 1, J. L. Riley III 1, C. J. Vierck 3, A. P. Mauderli 2 1 Community Dentistry & Behavioral Sci., Univ. of Florida Coll. of Dentistry, Gainesville, FL, USA, 2 Prosthodontics, Univ. of Florida Coll. of Dentistry, Gainesville, FL, USA, 3 Neuroscience, Univ. of Florida Coll. of Med., Gainesville, FL, USA Poster # 204 Participants. All participants recruited from clinics at the University of Florida. Healthy controls (n=37) were also recruited. Heat Stimulus: Focal thermal stimuli (  C) was administered by a Peltier-based thermode (23mm x 23mm). Stimulus Intensity Response Function (Experiment 1): Sensitivity along the segmental axis (lateral aspect of the calf; volar forearm; cheek) was assessed with an incremental series of thermal contact pulses (3 second duration; 30 second inter-stimulus interval, ISI). Prolonged Stimulation and Temporal Integration (Experiment 2): Sensitivity to a prolonged pulse was assessed over 4 consecutive series (25 brief thermal contact pulses per series). The contact duration was 0.9 sec throughout the experiment, the inter-stimulus-interval (ISI) was 2.5 sec for series 1 and 3; and 3.5 sec for series 2 and 4. Temperature was automatically adjusted to produce a pain rating around 35% based on reported pain ratings (eVAS). 18 “Sensitization index” for the brief and prolonged series of thermal stimuli. Temperature differences between healthy controls and each of the pain groups are presented as a function of test and site (derived by difference scores), which will be interpreted as a measure of sensitization. These finding should make us all famous and keep us working for years. A little more text to push the box down – there. Figure 1. Differences between pain groups and healthy controls regarding levels of pain intensity across sites on the cheek, forearm, and calf. Overall, main effects were observed for pain ratings (F (2,364) = , p < 0.001; higher levels of pain were observed with higher temperatures), stimulation site (F (2,182) = 5.073, p < 0.01), and group (F (3,91) = 3.514, p = 0.018] ; pain groups were more sensitive than healthy controls). Differences between pain groups and healthy controls regarding temperature of the thermode to maintain a pain intensity rating of 35% (automatically adjusted). All patient groups were significantly more sensitive to thermal nociceptive stimulation (i.e., the temperatures needed for eliciting a given pain intensity level were lower), when compared to their healthy counterparts. Significant main effects of group [F (3, 81) = 8.428, p 0.05) indicating that a similar pattern across the 4 series was seen for all 4 of the groups. Analysis of group means. The control group required a higher temperature to maintain the targeted pain ratings than the three pain groups. Pair-wise confirmed that the FMS, TMD, and IBS groups were significantly different from the controls (p 0.10). SERIES1234 ISI Mean temp Controls50.4 (1.2)51.3 (1.4)49.8 (1.2)50.9 (1.4)50.6 (1.2) FMS47.7 (3.0)7.9 (3.8)46.6 (3.3)47.3 (3.4)47.6 (2.7) TMD47.5 (2.5)48.2 (2.7)47.0 (3.1)47.8 (2.9)47.3 (3.2) IBS46.7 (3.4)47.4 (4.1)46.1 (4.0)47.0 (4.1)46.8 (4.0) All subjects48.5 (2.8)49.2 (3.3)47.8 (3.1)48.7 (3.3) All temperatures are represented in Celsius (  C) units. EXPERIMENT1112 Stimulation Parameters Experimental ProtocolSRC Prolonged Stimulation SiteCheekForearmCalfPalm Skin typeHairy Glabrous Difference from Controls FMS TMD1.7* IBS *3.8 All temperatures are represented in Celsius (  C) units. RESULTS INTRODUCTION This project was supported by NIH R , K , AARP and UF CTSI. Special thanks to my mom, and the staff of PRICE, and many UF student volunteers. INTRODUCTION RESULTS METHODS RESULTS SUMMARY