The free-exploratory paradigm as a model of trait anxiety in female rats: Test-retest reliability

The free-exploratory paradigm has been proposed as a model of trait anxiety and as such has been proven stable over time, which is a sine qua non condition for any model proposing to evaluate a personality trait. However this stability has only been shown for male rats. Considering that anxiety disorders are most prevalent in women, it's crucial that females are tested in animal models. With this in mind, the stability over time of female rats in the free-exploratory paradigm was evaluated using a test-retest procedure. The behaviour of drug-naive, adult, female, Wistar rats was measured in the free-exploratory apparatus on two occasions two months apart. The following parameters were evaluated: percentage of distance travelled in the novel compartment; number of attempts to enter the novel compartment; percentage of time spent in the novel compartment; and percentage of time rearing in the novel compartment. Subsequently, the intraclass correlation coefficient (ICC) and the kappa index (κ) were calculated for each of these parameters. The “percentage of time spent in the novel compartment” (ICC = 0.727; κ = 0.457), the “percentage of distance travelled in the novel compartment” (ICC = 0.680; κ = 0.370), and the “percentage of time rearing in the novel compartment” (ICC = 0.648; κ = 0.309) were found to be stable over time. Analysis of these parameters indicated fair to substantial reliability over time in two-month inter-trial interval. Therefore, our results support the idea of the free-exploratory paradigm as an animal model of trait anxiety for female rats.