Heterogeneity in the performance of outbred sprague-dawley rats in an elevated-plus maze test: A possible animal model for anxiety disorder

A wide variation in the performance of inbred rats measured in the elevated plus maze test suggests a possible genetic basis for anxiety response (AR). To gain further insight into the role of genetics in AR, we have characterized AR in male outbred S-D rats. Rats were placed in the black compartment (BC) facing the wall opposite the aperture and time needed for the animal to exit BC was noted. All rats underwent 3 successive trials 1–1.5 hrs apart. Naive rats showed a wide variation in their AR in trial 1(mean = 89 ± 19 sec, range = 5–360 sec). Sixty-eight % of the rats exhibiting low AR exited BC in <30sec, whereas 16% stayed in for the entire 360 sec (high AR). On successive testing, there was a progressive increase in AR which reached to max on second trial (Trial 1: 89±19, Trial 2: 171± 23, Trial 3: 210± 22 sec, p<0.0001). The time spent in BC on successive trials increased for most rats ($\text{33}\text{44}$), decreased for some ($\text{2}\text{44}$), showed min to no change ($\text{5}\text{44}$) or erratic response ($\text{4}\text{44}$) for others. In conclusion wide variation in the AR in outbred rats could be exploited to study genetic and neurochemical mechanisms of anxiety.