[Is "scopolamine-induced amnesia" in rats the result of state-dependent learning?]

The effects of a single and repetitive administration of m-cholinoblocker scopolamine (Sc) to male rats on retention of step-through passive avoidance (PA) or active avoidance (AA) in a shuttle-box were compared. In case of PA Sc (1 mg/kg) was injected i.p. only 30 min before training, only 30 min before testing, or both before training and before testing. In case of AA Sc (0.5 mg/kg/day) was injected i.p. only 15 min before each training session or both before training and before testing (44 days after achievement of learning criterion). The PA and AA retention were impaired only in the experiments, where the drug was administered before training, but did not differ from control, when Sc was injected twice. The Sc-induced amnesia (like many other cases of memory deficits) is suggested to be a manifestation of state-dependent learning. Similarity between the brain state during memory consolidation and during the retention test is necessary for recollection.