Thermal latency studies in opiate-treated mice.

BACKGROUND

The change in the reaction time of a tail or paw exposed to a thermal stimulus is a measure of nociceptive activity in laboratory animals. Tail-flick and plantar thermal sensitivity (Hargreaves) tests are non-invasive, minimize stress, and can be used to screen animals for phenotype and drug activity.

OBJECTIVE

Hargreaves testing has been widely used in rats. We investigated its use to measure the activity of opiate analgesia in mice.

METHODS

Mice were used in thermal stimulus studies at 1-5 hours and 1-5 days to test acute and extended release preparations of buprenorphine.

RESULTS

Hargreaves testing had limited value at 1-5 hours because mice can have an obtunded response to opiate therapy. Tail-flick studies with restrained mice are not affected by the initial locomotor stimulation.

DISCUSSION

The present report describes a simple restraint system for mice. The utility of the system is demonstrated by examining the efficacy of acute and extended release buprenorphine injections in Balb/c and Swiss mice.

CONCLUSION

Standardized tail-flick testing provides a sensitive robust method to monitor opiate activity in mice.