A Novel Role Of ASICs In Immediate Exercise-Induced Pain And Exercise Performance

Abstract

D-13 Thematic Poster - RPE, Pain and Fatigue Thursday, May 28, 2020, 1:30 PM - 3:30 PM Room: CC-2011 INTRODUCTION: Exercise training is an effective therapy for many pain-related conditions, and there is a difference in pain perception between athletes and unconditioned people. The mechanisms by which exercise modulates pain are poorly understood. Painful conditions can be associated with elevated levels of protons, metabolites and inflammatory factors, which can activate receptors and/or ion channels on nociceptive sensory neurons including acid sensing ion channels (ASICs) and transient receptor potential cation channel subfamily V member 1 (TRPV1). Additionally, strenuous exercise also causes the release of similar chemical signals, and ASICs within muscle afferents may mediate immediate exercise-induced pain (IEP) and fatigue, as well as reflex hemodynamic changes. We hypothesized that ASICs and TRPV1 have role in IEP and maximal exercise performance. METHOD: First, C57BL/6 mice were divided into sedentary (SED), low-intensity continuous training (LICT) and high-intensity interval training (HIIT) groups. Mice were trained on a treadmill every other day for 4 weeks. SED mice were placed on a non-moving treadmill for similar periods of time. After 4 weeks, exercise performance, ASICs and TRPV1 mRNA levels within lumbar dorsal root ganglion (DRG) were measured. In a separate group, we measured IEP at baseline and following exhaustive exercise before and after HIIT. In a third study, we compared the IEP and exercise performance in ASIC3-/- versus wild type (WT) mice. RESULTS: We found HIIT improved exercise performance compared to LICT and sedentary groups, diminished ASICs and TRPV1 mRNA levels in lumber DRG, and reduced IEP. We also found a negative relationship between mRNA levels of ASICs and TRPV1 and exercise performance (r = - 0.59, p < 0.001). In addition, ASIC3-/- showed a significant lower IEP compared to WT mice, while there was no difference in maximal exercise performance between groups. CONCLUSION: In summary, ASIC3 is required for IEP following exhaustive exercise, and exercise training downregulates ASICs and TRPV1 in muscle afferents and diminishes IEP. These findings suggest a possible role of ASICs in benefits of exercise training for many pain and fatigue conditions such as fibromyalgia and chronic fatigue syndrome conditions. Supported by Department of Veteran Affairs.