von Frey / Carrageenan Allodynia Assay

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Allodynia is an abnormal nociceptive response to a stimulus that does not provoke pain under normal conditions. This model is included in our battery of analgesia assays as a touch sensitivity assay using Semmes-Weinstein monofilaments (i.e. von Frey filaments).

The von Frey Test assesses the sensitivity and pain responses of Carrageenan-challenged animals to thin hair-like filaments of varying diameter and the corresponding force needed to bend the fiber.

Intraplantar carrageenan has been demonstrated to increase sensitivity of the rodent hind paw and is commonly used in allodynia assays. Von Frey filaments are typically used to ascertain the mechanoreceptor threshold level and the ability of a test agent to affect the mechanoreceptor response. They are therefore ideal to evaluate carrageenan sensitivity.

A number of pharmacological agents are effective in reducing the sensitivity of mice to von Frey stimuli including serotonin reuptake inhibitors, anti-inflammatory agents, GABA enhancers and opioids. This assay is included in the battery of analgesia assays that include the thermal nociceptive assay and the formalin chemical nociceptive assay.

Injected Paw Measurement 2 Hrs Post Carrageenan

Animals were injected with 1% carrageenan into the right hind paw and acclimated to the testing environment. Thirty minutes prior to testing, mice were injected with vehicle or Indomethacin. Two hours post-Carrageenan challenge, von Frey mechanical fibers are applied to the plantar surface of each paw to elicit a nociceptive response. Indomethacin significantly increased mechanical thresholds post-carrageenan challenge compared to vehicle treated mice.
Data are mean ± SEM (N=8); ***p<0.0001 compared to vehicle.

Comparison of Injected Paw

An additional comparison was performed to evaluate differences at baseline vs. post-Carrageenan challenge. Both treatment groups prior to dosing had similar thresholds at baseline. However, two hours after the Carrageenan challenge, vehicle treated mice had significantly reduced thresholds compared to Indomethacin treated mice.
Data are mean ± SEM (N=8); *p<0.05 compared to baseline vehicle.

The von Frey Test with Carrageenan Allodynia is typically run in an acute mode (study completed in one day) by evaluating test articles after a single administration. The variability is relatively low and statistical significance may be achieved with group sizes of about 8 to 10 animals. It can be performed in both mice and rats.