Scopolamine impairs response-to-change based on distal cues in the rat.

The effect of a scopolamine injection (1 mg/kg, IP) on response-to-change behavior was investigated in two experiments. After exploration of a T-maze with one arm black and the other white (Trial 1), rats were tested with both arms either black or white (Trial 2). Experiment 1 revealed that the opportunity to make body turns into the arms did not help scopolamine-injected rats to locate the changed arm after visual exploration of the arms during Trial 1. Saline-injected animals chose the changed arm. In Experiment 2, rats were allowed to move freely into the arms during Trial 1. During Trial 2, they were tested either from the same start as that used during Trial 1 or from a different start 180 degrees from the original start. While scopolamine-injected animals reacted appropriately to the change when tested from the same start, they were impaired when tested from the opposite start. In both conditions, saline-injected animals chose the changed arm. These results, together with others, support the notion that the cholinergic system plays a crucial role in the processing of distal information.