Role of ASIC3 in the primary and secondary hyperalgesia produced by joint inflammation in miceIkeuchi, M.1; Kolker, S. J.1; Burnes, L. A.; Walder, R. Y.; Sluka, K. A.*PAIN: July 31st, 2008 - Volume 137 - Issue 3 - p 662–669 doi: 10.1016/j.pain.2008.01.020 Research papers Buy SDC Abstract Author InformationAuthors Article MetricsMetrics The acid sensing ion channel 3 (ASIC3) is critical for the development of secondary hyperalgesia as measured by mechanical stimulation of the paw following muscle insult. We designed experiments to test whether ASIC3 was necessary for the development of both primary and secondary mechanical hyperalgesia that develops after joint inflammation. We used ASIC3 −/− mice and examined the primary (response to tweezers) and secondary hyperalgesia (von-Frey filaments) that develops after joint inflammation comparing to ASIC3 +/+ mice. We also examined the localization of ASIC3 to the knee joint afferents innervating the synovium using immunohistochemical techniques before and after joint inflammation. We show that secondary mechanical hyperalgesia does not develop in ASIC3 −/− mice. However, the primary mechanical hyperalgesia of the inflamed knee joint still develops in ASIC3 −/− mice and is similar to ASIC3 +/+ mice. In knee joint synovium from ASIC3 +/+ mice without joint inflammation, ASIC3 was not localized to joint afferents that were stained with an antibody to protein gene product (PGP) 9.5 or calcitonin gene-related peptide (CGRP). ASIC3 was found, however, in synoviocytes of the knee joint of uninflamed mice. In ASIC3 +/+ mice with joint inflammation, ASIC3 co-localized with PGP 9.5 or CGRP in joint afferents innervating the synovium. We conclude that the decreased pH that occurs after inflammation would activate ASIC3 on primary afferent fibers innervating the knee joint, increasing the input to the spinal cord resulting in central sensitization manifested behaviorally as secondary hyperalgesia of the paw. Physical Therapy and Rehabilitation Science Graduate Program, Pain Research Program, University of Iowa, Iowa City, IA 52242, USA *Corresponding author. Tel.: +1 319 335 9791; fax: +1 319 335 9707. E-mail: firstname.lastname@example.org 1These authors contributed equally to this work. E-mail: email@example.com Submitted October 12, 2007; received in revised form December 11, 2007; accepted January 22, 2008. © 2008 Lippincott Williams & Wilkins, Inc.