Breeder differences within Wistar strain rats in step-through type passive avoidance response

Characteristics of acquisition and retention of the one-training and repeated-training passive avoidance responses of the step-through type were investigated in 3 lines of so-called Wistar strain rats: HLA:Wistar, JLA:Wistar and Std:Wistar and in F344/Du Crj rats. In the adaptation and the first acquisition trials in the repeated-training task, Std:Wistar rats took comparatively longer latency times to enter the dark chamber from an illuminated runway than the other lines and strain of rats. In contrast, JLA:Wistar rats took a number of trials to stay for 300 sec or longer in the runway. HLA:Wistar, Std:Wistar and F344/Du Crj rats showed similar response latencies in the first retention trial. JLA:Wistar rats showed the shortest latencies among 3 lines of Wistar and F334/Du Crj rats, exhibiting much poorer acquisition and retention abilities than the other rats. The response latencies in the retention trials were longer in the order of HLA:Wistar greater than or equal to F344/Du Crj greater than Std:Wistar greater than JAL:Wistat rats. These results suggest that there are marked breeder differences in their passive avoidance response even in the rats that have the same strain name.