Ankle joint mobilization affects postoperative pain through peripheral and central adenosine A1 receptors

Abstract

Background. Physical therapists frequently use joint mobilization therapy techniquesto treat people with musculoskeletal dysfunction and pain. Several studiessuggest that endogenous adenosine may act in an analgesic fashion in various painstates. Objective. The purpose of this study was to investigate the contribution of theadenosinergic system on the antihyperalgesic effect of ankle joint mobilization (AJM).Design. This was a experimental study. Methods. To test the hypothesis that the adrenosinergic system is involved in theantihyperalgesic effect of AJM, mice (25-35 g) submitted to plantar incision surgerywere used as a model of acute postoperative pain. The mice were subjected to AJMfor 9 minutes. Withdrawal frequency to mechanical stimuli was assessed 24 hoursafter plantar incision surgery and 30 minutes after AJM, adenosine, clonidine, ormorphine treatments. The adenosinergic system was assessed by systemic (intraperitoneal),central (intrathecal), and peripheral (intraplantar) administration of caffeine.The participation of the A1 receptor was investigated using a selective adenosine A1 receptor subtype antagonist. In addition, previous data on the involvement of theserotonergic and noradrenergic systems in the antihyperalgesic effect of AJM wereconfirmed.Results. Ankle joint mobilization decreased mechanical hyperalgesia, and thiseffect was reversed by pretreatment of the animals with caffeine given by intraperitoneal,intraplantar, and intrathecal routes. In addition, intraplanar and intrathecaladministrations of 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, a selective adenosineA1 subtype receptor antagonist) or systemic administration of yohimbine or-chlorophenylalanine methyl ester hydrochloride (PCPA) blocked the antihyperalgesiainduced by AJM.Limitations. The results are limited to animal models and cannot be generalizedto acute pain in humans. Conclusions. This study demonstrated the involvement of the adenosinergicsystem in the antihyperalgesic effect of AJM in a rodent model of pain and providesa possible mechanism basis for AJM-induced relief of acute pain. © 2013 American Physical Therapy Association.