['We investigated possible differences in the impact of chronic amphetamine administration during adolescence and adulthood on aspects of behaviour and brain chemistry.', 'Adult (n=32) and adolescent (n=32) male Sprague-Dawley rats were given either D-amphetamine sulphate (10 mg kg(-1) daily, i.p.) or saline (1 mL kg(-1), i.p.) for 10 days. Rats were subsequently tested for anxiety-like behaviour, learning and memory, and sensorimotor gating. Nine weeks later, rats received saline (1 mL kg(-1)) or acute amphetamine challenge (1.5 mg kg(-1)) and the expression levels of mRNA for tyrosine kinase B (TrkB) or cAMP response element-binding protein (CREB) were measured in the hippocampus.', 'The adolescent amphetamine pretreated group revealed a deficit in exploration on the Y-maze during a 6 h retention test. The frequency of visits to the novel arm was 35% lower for the amphetamine group compared with controls. In parallel, a 43% decrease in hippocampal CREB mRNA, but not TrkB mRNA, was observed in periadolescent rats treated chronically with amphetamine 9 weeks earlier. None of the effects were detected in the adult treated cohort.'] Does persistent downregulation of hippocampal CREB mRNA parallel a Y-maze deficit in adolescent rats following semi-chronic amphetamine administration?