Pre-exposure of rats to amphetamine sensitizes self-administration of this drug under a progressive ratio schedule

Psychopharmacology (Berl). 1998 Feb;135(4):416-22. doi: 10.1007/s002130050530.


Two groups of male rats were tested to determine whether pre-exposure to d-amphetamine would enhance the motivation to self-administer the drug under a progressive ratio schedule of reinforcement. In the first phase of the experiment, one group of rats received d-amphetamine (2 mg/kg IP), while a second group received saline on alternate days for a total of ten injections. Following a 21-day drug withdrawal period, behavioral sensitization was confirmed by a significant increase in amphetamine-induced stereotypy in the d-amphetamine-pretreated group, relative to the saline-pretreated group. In the second phase of the study, all rats were implanted with chronic jugular catheters and trained to self-administer d-amphetamine (0.2 mg/kg per infusion) under a fixed-ratio schedule of reinforcement. The progressive ratio paradigm was then imposed for 7 consecutive days; d-amphetamine-pretreated rats attained significantly higher break points than saline-pretreated animals. These data suggest that pre-exposure to d-amphetamine may enhance the motivation to self-administer this drug.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Central Nervous System Stimulants / pharmacology*
  • Conditioning, Operant / drug effects*
  • Dextroamphetamine / pharmacology*
  • Male
  • Motor Activity / drug effects
  • Rats
  • Reinforcement Schedule
  • Self Administration
  • Stereotyped Behavior / drug effects


  • Central Nervous System Stimulants
  • Dextroamphetamine