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Increased glutamate and decreased glycine release in the rostral ventromedial medulla during induction of a pre-clinical model of chronic widespread muscle pain
Journal article   Open access   Peer reviewed

Increased glutamate and decreased glycine release in the rostral ventromedial medulla during induction of a pre-clinical model of chronic widespread muscle pain

Rajan Radhakrishnan and Kathleen A Sluka
Neuroscience letters, Vol.457(3), pp.141-145
2009
DOI: 10.1016/j.neulet.2009.03.086
PMID: 19429181
url
http://doi.org/10.1016/j.neulet.2009.03.086View
Open Access

Abstract

Two injections of acidic saline into the gastrocnemius muscle produce long-lasting hyperalgesia that is initiated and maintained by changes in the rostroventromedial medulla (RVM). Potential underlying mechanisms could be increased release of excitatory neurotransmitters and/or reduced release of inhibitory neurotransmitters, in the RVM. We tested this hypothesis by measuring concentrations of aspartate, glutamate and glycine in response to the first and second injection of acidic saline and compared to intramuscular injections of normal saline using microdialysis with HPLC analysis. We show a significant increase in aspartate and glutamate during the second acidic saline injection compared to normal saline injections or the first injection of acidic saline. There were also long-lasting decreases in glycine concentrations in the RVM in response to both the first and second injection of acidic saline. It is possible that disinhibition after the first injection leads to long-lasting neuronal changes that allow a greater release of excitatory neurotransmitters after the second injection. We hypothesize that increased release of excitatory neurotransmitters in the RVM drives the release of excitatory neurotransmitters in the spinal cord, central sensitization and the consequent hyperalgesia.
Aspartate Pain Microdialysis HPLC Hyperalgesia

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