Adolescent Rats Exposed to Amphetamine Manifest Learning and Memory Deficits As Drug Free Adult Animals.

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Conference Proceeding

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Amphetamine (AMPH) is a psychomotor stimulant medication used in the therapeutic management of attention deficit / hyperactivity disorder (ADHD). Although the prescribed use of AMPH-like medications in children aged 9 to 17 has increased nationally in recent decades, few research studies have comprehensively assessed the effects of chronic AMPH exposure during the adolescent phase of laboratory animal development. Experiments in this series characterized long term cognitive effects subsequent to daily AMPH injections administered during the adolescent stage of rat development. AMPH treatment (7.5 mg / kg, s.c.) was started in pubescent rats (40th postnatal day [PND40]) and continued to adulthood (PND90). AMPH treated rats were compared to age / gender matched saline-injected rats whilst navigating a 14-unit complex-T-maze. Complex-T (C/T) mazes provide a venerable method of assessing learning through choice efficacy. Subjects navigating a C/T maze are confronted at various points with two seemingly similar paths; one path leads to food and the second path dead ends. With repeat exposure to the C/T maze, an un-drugged animal learns to turn before entering orthogonal T juncture points. Normal, undrugged animals also learn to backtrack when T junctures toward a blind alley are crossed, thereby avoiding culs-de-sac dead ends. Rats for the present study were maintained on a once daily feeding schedule, after maze testing, to motivate speedy maze navigation. Foot shocks were introduced only in instances of slow maze maneuvering. The time animals took to reach a goal box containing food rewards was measured on a stop watch. Each rat’s performance was monitored in 70 trials, scheduled 5 trials per day, with a 2 min intertrial interval. Data from these sessions revealed a difference in key performance indicators (total errors, run time, shocks delivered) for AMPH-treated relative to saline-treated rats. Our findings emphasize a need for further research to improve scientific understandings of stimulant drug effects in a developing nervous system, specifically evaluating whether or not stimulant drug use sustains enduring effects after drug exposure stops