"Currently available behavioral assays to quantify normal temperature sensitivity, hypersensitivity, hyperalgesia and temperature preference/avoidance in mice have created conflicting results in the literature.
Some only capture a limited spectrum of thermal experiences, others are prone to experimenter bias or are not sensitive enough to detect the contribution of ion channels to temperature sensing because in mice smaller alterations in temperature preference may not manifest as explicit behavioral changes or may be masked by confounding factors and require high sensitivity.
To overcome current limitations, we have designed a novel device that is automated, provides a high degree of freedom, i.e. thermal choice, and eliminates experimenter bias. The device represents a thermal gradient assay designed as a circular running track. It allows discerning exploratory behavior from thermal selection behavior and provides increased accuracy by providing measured values in duplicate and by removing edge artifacts.
The assay delivers discrete information on a large range of parameters extracted from the occupancy of thermally defined zones such as preference temperature and skew of the distribution.
We demonstrate that the assay allows increasingly accurate phenotyping of thermal sensitivity in transgenic mice by disclosing yet unrecognized details on the phenotypes of TRPM8-, TRPA1- and TRPM8/A1-deficient mice." From "Comprehensive thermal preference phenotyping in mice using a novel automated circular gradient assay (Touska et al. 2016)"
Other scientists, like the M. Tominaga team in Japan, the R. Russo in Naples and the Tegeder team in Germany showed applications in Parkinson’s disease and chronic pain, TRP knock-out mice behaviors and testing of molecule candidates to interact with TRP receptors, which have been shown to be a valuable pharmacological option several therapeutic areas.
The paper "Thermal gradient ring for analysis of temperature-dependent behaviors involving TRP channels in mice", pubblished in 2024, describes the TGR method and compares its benefits to current methods for temperature preference and avoidance studies.