The effects of apomorphine and haloperidol on memory consolidation in the day-old chick.

Apomorphine was found to disrupt memory consolidation in a dose-dependent manner on chicks trained on a 1-trial passive avoidance task with a strong aversant experience. Chicks injected with 4.0 mg/kg apomorphine displayed memory deficits at 180 min after learning and showed marked behavioral disturbances, including increased locomotion and increased pecking at the feet of conspecifics. Pretreatment with the dopamine antagonist haloperidol eliminated the memory disturbance induced by apomorphine and facilitated consolidation of memory in chicks given a weak (20% vol/vol methyl anthralinate) training experience. Time-of-retention data suggested that the memory disruption occurred from 120 min after learning, leading to the suggestion that dopamine-related modulation of the training experience may be involved in late-memory formation processes.