Abstract
Purpose: When two patterns of behavior, forepaw licking and jumping, were used as criteria for the hot-plate test, a disagreement between the results was reported. We hypothesized that the two behavior patterns represent different indexes for pain sensitivity, pain threshold and pain tolerance level The aim of the present study was to investigate this hypothesis. Methods: Latency until forepaw licking and jumping was measured in each mouse using the hot-plate test at times between 10:00 and 12:00h. The latency times were compared for several stimulation intensities (45-65°C). Results: Both reaction times based on forepaw licking and jumping increased as the stimulation intensity decreased (one-way ANOVA, p<0.05). The jumping response was more sensitive to changes in stimulation intensity than the forepaw licking response. The series of jumping reaction times was longer than the forepaw licking reaction times (two-way ANOVA, p<0.01). A significant correlation between the licking and jumping latencies was not observed at any stimulation intensity. Conclusion: Forepaw licking and jumping are the recommended indexes for pain threshold and pain tolerance level, respectively, during the hot- plate test.
