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Assessing carrageenan‐induced locomotor activity impairment in rats: Comparison with evoked endpoint of acute inflammatory pain
Author(s) -
Zhu C.Z.,
Mills C.D.,
Hsieh G.C.,
Zhong C.,
Mikusa J.,
Lewis L.G.,
Gauvin D.,
Lee CH.,
Decker M.W.,
Ban A.W.,
Rueter L.E.,
Joshi S.K.
Publication year - 2012
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1002/j.1532-2149.2011.00099.x
Subject(s) - carrageenan , nociception , ibuprofen , anesthesia , medicine , hyperalgesia , gabapentin , duloxetine , analgesic , morphine , saline , pharmacology , receptor , alternative medicine , pathology
Background Most animal models currently used to evaluate antinociceptive efficacy of analgesics rely on the assessment of evoked pain behaviours as primary endpoints. Mehtods Here, we have developed and characterized the carrageenaninduced locomotor activity impairment ( CLAIM ) model to objectively assess non‐evoked inflammatory pain behaviour in rats. In this model, 100 µL of 1% carrageenan was subcutaneously injected into the plantar aspect of the right hind paw and exploratory behaviour in the novel testing chamber was recorded using an automated locomotor activity system. Results Carrageenan‐injected animals exhibited an exploratory behavioural deficit 2–7 h following injection compared to saline‐injected animals. The severity of impairment was carrageenan dose related, and sensitive to the light intensity in the testing room. The effects of standard analgesics on CLAIM were examined 2 or 3 h following carrageenan injection. Diclofenac and ibuprofen, in a dose range exerting no effect on locomotor activity in naïve rats, exhibited dose‐related reversal of CLAIM ( ED 50 = 1.5 and 5.0 mg/kg, respectively), with comparable efficacy on carrageenan‐induced thermal hyperalgesia ( ED 50 = 2.0 and 6.0 mg/kg, respectively). Gabapentin and duloxetine produced no reversal of CLAIM , or attenuation of thermal hyperalgesia. Efficacy discrepancy was noted for morphine on thermal hyperalgesia and CLAIM . Additionally, amphetamine dose dependently reversed CLAIM , and similarly increased locomotor activity in normal animals. Discussion and Conclusion The results presented here demonstrate that CLAIM provides an objective assessment of non‐evoked pain behaviours for acute inflammatory pain. The pharmacological profile of standard analgesics supports that CLAIM model can be used to identify agents to treat acute inflammatory pain in the clinic.