Effects of post-training d-amphetamine on acquisition of an appetitive autoshaped lever press response in rats

This experiment examined the effect of post-training d-amphetamine on retention in an appetitive autoshaping conditioning situation. Harlan Sprague-Dawley rats were first given ten autoshaping trials, followed by either three or four additional sessions of 50 trials (70 s intertrial interval) on which the conditioned stimulus (the extension of an illuminated Plexiglas lever for 10 s) and unconditioned stimulus (a 45 mg food pellet), were paired. d-Amphetamine (1 or 2 mg/kg) or saline was administered IP either immediately or 2 h following training. Rats injected with 1 mg/kg d-amphetamine immediately after the first training session made significantly more responses during the conditioned stimulus presentation on the following daily session of 50 trials. Thus, the amphetamine-treated rats acquired the lever press response faster than those given only saline. The amphetamine effects were time dependent: no significant effects were found if the injection was delayed until 2 h following training. These results agree with the findings of other instrumental aversive facilitation studies and suggest that d-amphetamine may enhance retention of the classically conditioned components of autoshaping.