Dissociating the primary reinforcing and reinforcement-enhancing effects of nicotine using a rat self-administration paradigm with concurrently available drug and environmental reinforcers

Psychopharmacology (Berl). 2006 Mar;184(3-4):391-400. doi: 10.1007/s00213-005-0183-4. Epub 2005 Oct 25.


Rationale: Nicotine has two effects on reinforcement in traditional self-administration paradigms. It serves as a primary reinforcer by increasing the probability of behaviors that result in nicotine delivery. However, nicotine also potently enhances behaviors that result in the delivery of nonpharmacological reinforcers.

Objectives: The present study sought to dissociate these two effects of nicotine on reinforcement.

Methods: For one group of rats (2 lever), a nonpharmacological reinforcer [visual stimulus (VS)] was available for pressing one lever. Nicotine infusions were available for pressing a different lever. A second group (NIC + VS) received more traditional self-administration training; both the VS and nicotine were delivered for pressing a single active lever. Control groups received either nicotine infusions (NIC only) or VS presentations (VS only) for pressing the active lever.

Results: Nicotine alone was a weak reinforcer; the VS alone was slightly more reinforcing than nicotine. When these two reinforcers were combined (NIC + VS), response rates were synergistically increased. For the 2-lever group, responding on the nicotine lever was weak, matching the response rates of rats receiving nicotine alone. However, responding on the VS lever was potently enhanced in this group; equaling the response rates for rats receiving both reinforcers for making a single response (NIC + VS).

Conclusions: These data indicate that the reinforcement-enhancing effects of nicotine are very potent even when only moderate quantities of the drug are self-administered. Moreover, they provide the first demonstration that the reinforcement-enhancing and primary reinforcing effects of nicotine can be dissociated behaviorally.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Association Learning
  • Cues*
  • Disease Models, Animal*
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Infusions, Intravenous
  • Male
  • Motivation
  • Psychomotor Performance
  • Rats
  • Rats, Sprague-Dawley
  • Reinforcement, Psychology*
  • Self Administration
  • Social Environment*
  • Tobacco Use Disorder / psychology*
  • Visual Perception