Differences in the acquisition process and the effect of scopolamine on radial maze performance in three strains of rats.

The acquisition process and the effect of scopolamine (SCOP) on the radial maze task were studied in 3 strains of male rats, Fischer 344 (F344), Sprague-Dawley (SD) and Wistar. The pretraining level of locomotor activity was measured and performance was quantitatively and qualitatively evaluated. The highest pretraining locomotor activity was observed in Wistar rats. In this experiment, rats were allowed to select each arm successively. The changes in the number of correct choices during the first eight selections, error choice in a trial and the total duration of a trial differed with the strain in the first 5 training sessions. Acquisition curve for F344 rats gradually rose. Wistar rats made many error choices. However, during the final 5 sessions, only the total duration of a trial differed with the strain. Wistar rats took the shortest time to finish a trial, but the number of sessions taken to acquire this task was the fewest with F344 rats, and the most with Wistar rats. The effect of SCOP differed among strains in all the above 3 indexes. Generally, the Wistar rat was the most affected by the injection of SCOP. Moreover, the change of the choice accuracy and the spatial strategy by the administration of SCOP were investigated. SD and Wistar rats showed a dose-dependent decrease in choice accuracy in the earlier selection. The spatial strategy was changed in every strain by the injection of SCOP. These findings do not support the previous finding that a high level of locomotor activity yields fast acquisition of this task or that Wistar rats are better in learning than SD, but indicates that SCOP affects not only the working memory but also the motivational factor.