Persistent increase in the motivation to take heroin in rats with a history of drug escalation

Neuropsychopharmacology. 2000 Apr;22(4):413-21. doi: 10.1016/S0893-133X(99)00133-5.


The transition from stable to escalated levels of cocaine self-administration has been shown to depend upon drug availability. The generality of this phenomenon is assessed here by studying the effects of availability on heroin self-administration. Two groups of rats were trained on a 1-h continuous schedule of self-administration, after which, access to heroin (40 microg/injection) was increased to 11 h in one group (long access or LgA rats) or kept to 1 h in the other group (short access or ShA rats). After 18 sessions on this regimen, both ShA and LgA rats were tested for extinction and stress-induced reinstatement of heroin-seeking behavior. In LgA rats, both total and first hour intake gradually escalated over time. After escalation, LgA rats were slower to extinguish heroin-seeking behavior and responded more to the reinstating effect of stress after extinction. These findings show that: (1) the escalation process in drug consumption is common to both opiate and stimulant self-administration; (2) escalation in heroin consumption is associated with a persistent increase in the motivation for taking heroin.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Heroin / pharmacology*
  • Male
  • Motivation*
  • Psychomotor Performance
  • Rats
  • Rats, Wistar
  • Self Administration / psychology*
  • Substance-Related Disorders / physiopathology*
  • Substance-Related Disorders / psychology*


  • Heroin