Effects of atropine on response-to-change.

The effect of atropine on rats response to the change of brightness was investigated in a T-maze, in two procedural test versions differing in the exposure of visual stimuli. In the passive test the rats could observe the white and black arms through clear partitions which blocked the entrance to the arms, while in the active test they were allowed to explore the maze arms. In the subsequent free choice trial, when both arms were of the same brightness (either white or black) atropine in a dose of 16 mg/kg, injected 10 min prior to the exposure of stimuli, affected the rats' performance in the passive test. The druged rats showed random selection of the arms, whereas 80 percent of saline controls chose the arm whose brightness had been changed. In the active test the same dose of atropine had no effect on the choice behavior. Both atropine and saline groups showed a closely similar preference for the changed arm. The effect of atropine on response-to-change was compared to that of scopolamine investigated by us in the previous study.