Does behavioral response to novelty influence paw withdrawal latencies in repeated Hargreaves test?

Sa？etak Background and Purpose: Only recently, we have reported that single retesting session significantly decreases rat paw withdrawal latencies (PWL) in Hargreaves tests.We wondered, whether decrease in PWL values obtained during reexposure toHargreaves testmight be associated with reaction to the new environment. Therefore, we investigated PWL together with the open field behavior in an enclosure of the Hargreaves test device during the period of 3 subsequent days. Materials and Methods: Ten male Wistar rats were tested once a day. Each rat was first exposed to the open field behavior test for five minutes and then to the Hargreaves test. Rearing (vertical movements), grooming (animal cleaning its face or body), defecation, the distance travelled, time mobile and time immobile were recorded. Data were analyzed using one way ANOVA and Bonferroni test (PWL) or Kruskal Wallis and Mann Whitney U tests (open field behavior). Results: PWL significantly declined from the first to the second and third exposure to Plantar test device (ANOVA, P< 0,01; Bonferroni P< 0,05). Decline in PWL values was accompanied with concomitant increase in grooming (Kruskal Wallis P< 0.01; Mann-Whitney U test P< 0.05), decrease in rearing behavior (Kruskal Wallis P< 0.001; Mann-Whitney U test P< 0.001) and defecation during retesting sessions. Conclusion: Decrease in the PWL values obtained during reexposure to Hargreaves test device was accompanied by alterations in behavioral reactions to the new environment. Time course and direction of these changes suggest that reaction to novelty might be related to decrease in PWL values observed during retesting sessions of the Hargreaves test