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Joint manipulation reduces hyperalgesia by activation of monoamine receptors but not opioid or GABA receptors in the spinal cord
Journal article   Peer reviewed

Joint manipulation reduces hyperalgesia by activation of monoamine receptors but not opioid or GABA receptors in the spinal cord

D.A Skyba, R Radhakrishnan, J.J Rohlwing, A Wright and K.A Sluka
Pain (Amsterdam), Vol.106(1), pp.159-168
2003
DOI: 10.1016/S0304-3959(03)00320-8
PMCID: PMC2732015
PMID: 14581123

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Abstract

Joint manipulation has long been used for pain relief. However, the underlying mechanisms for manipulation-related pain relief remain largely unexplored. The purpose of the current study was to determine which spinal neurotransmitter receptors mediate manipulation-induced antihyperalgesia. Rats were injected with capsaicin (50 μl, 0.2%) into one ankle joint and mechanical withdrawal threshold measured before and after injection. The mechanical withdrawal threshold decreases 2 h after capsaicin injection. Two hours after capsaicin injection, the following drugs were administered intrathecally: bicuculline, blocks γ-aminobutyric acid (GABA A) receptors; naloxone, blocks opioid receptors; yohimbine blocks, α 2-adrenergic receptors; and methysergide, blocks 5-HT 1/2 receptors. In addition, NAN-190, ketanserin, and MDL-72222 were administered to selectively block 5-HT 1A, 5-HT 2A, and 5-HT 3 receptors, respectively. Knee joint manipulation was performed 15 min after administration of drug. The knee joint was flexed and extended to end range of extension while the tibia was simultaneously translated in an anterior to posterior direction. The treatment group received three applications of manipulation, each 3 min in duration separated by 1 min of rest. Knee joint manipulation after capsaicin injection into the ankle joint significantly increases the mechanical withdrawal threshold for 45 min after treatment. Spinal blockade of 5-HT 1/2 receptors with methysergide prevented, while blockade of α 2-adrenergic receptors attenuated, the manipulation-induced antihyperalgesia. NAN-190 also blocked manipulation-induced antihyperalgesia suggesting that effects of methysergide are mediated by 5-HT 1A receptor blockade. However, spinal blockade of opioid or GABA A receptors had no effect on manipulation induced-antihyperalgesia. Thus, the antihyperalgesia produced by joint manipulation appears to involve descending inhibitory mechanisms that utilize serotonin and noradrenaline.
Spinal cord Pain Serotonin Joint manipulation Capsaicin Noradrenaline

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