Female Wistar rats obtained from different breeders vary in anxiety-like behavior and epileptogenesis

Abstract

Outbred rats are widely used in biomedical research studies. The genotypic variation, different housing and handling conditions during development, and gender of used rats can be expected to cause variations in behavior and epileptogenesis. We tested the hypothesis that adult female Wistar rats from different breeders vary in anxiety-like behavior, seizure susceptibility, and epileptogenesis in the kindling model of temporal lobe epilepsy. In female Wistar rats from three different commercial breeders ([HsdCpb:WU], [Crl:WI(Han)], and [RjHan:WI]), anxiety-like behavior was monitored in the open field and the elevated plus maze. Wistar rats from Charles River showed lower locomotor activity and higher anxiety-like behavior compared to Wistar rats from Harlan-Winkelmann and Janvier. Female Wistar rats from Harlan-Winkelmann showed the lowest anxiety-like behavior and the highest exploratory behavior. Subsequently, rats were kindled by daily electrical stimulation of the right amygdala as a model of temporal lobe epilepsy. Wistar rats from Charles River exhibited significantly increased cumulative motor seizure duration and cumulative afterdischarge duration until seizure generalization compared to Harlan-Winkelmann and Janvier rats. In other words, Wistar rats from Charles River showed a longer time of focal seizures until generalization, reflecting a slower epileptogenesis in these rats. The initial afterdischarge threshold did not differ significantly between Wistar rats from the three breeders, indicating that baseline seizure susceptibility is not different between the three groups. In conclusion, female Wistar outbred rats from different breeders showed variations in anxiety-like behavior and epileptogenesis. Decisions about appropriate commercial colonies used for biomedical research should be taken with caution.