A technique to measure cold adaptation in freely behaving mice.

ABSTRACT

BACKGROUND: Adaptation to environmental temperature is essential for survival in seasonal areas. The mechanisms of adaptation have been studied in vitro, but it has not been quantified in vivo. NEW METHOD: The extended Cold Plantar Assay (eCPA) cools the entire testing environment. Once the desired environmental temperature has been reached, a separate focal cold stimulus is applied to the hindpaw and the latency to withdrawal is recorded as a proxy for cold sensitivity. RESULTS: Using this technique, we can test the cold responsiveness of freely behaving mice at ambient temperatures ranging from 5°C to 30°C. The responses are consistent and unambiguous, and the environmental temperatures generated are reproducible. We are also able to measure cold responsiveness as animals are in the process of adapting to cold environments. COMPARISON WITH EXISTING METHOD(S) Existing methods, such as the dynamic cold plate and the 2-plate preference assay test how mice respond to cold environments, but cannot assess how the thresholds for response are changed by acclimation in cold environments. Additionally, the eCPA requires very little specialized equipment, can test many mice at the same time on one apparatus, and has an objective readout. CONCLUSIONS: The extended Cold Plantar assay is a significant methodological improvement, allowing the assessment of cold responsiveness in freely behaving mice at a wide range of environmental temperature conditions and during cold adaptation.