Susceptibility to conditioned place preference induced by addictive drugs in mice of the C57BL/6 and DBA/2 inbred strains

Psychopharmacology (Berl). 2005 Sep;181(2):327-36. doi: 10.1007/s00213-005-2259-6. Epub 2005 Oct 14.

Abstract

Rationale: In previous studies, we have demonstrated that mice of the inbred strain C57BL/6J (C57) are more susceptible to amphetamine-induced conditioned place preference (CPP) than DBA/2J (DBA) mice. Moreover, we also observed parallel strain differences for the locomotor-stimulant effects of the drug. However, other studies have reported either no difference or opposite strain differences for cocaine- and morphine-induced CPP as well as for the locomotor effects of these drugs, suggesting that amphetamine-related behavioral phenotypes might depend on a specific pharmacological action of the psychostimulant.

Objectives: This study was aimed at testing strain differences for cocaine- and morphine-related behavioral phenotypes in the same experimental protocol and conditions previously used for amphetamine.

Methods: C57 and DBA mice were tested for CPP induced by cocaine (0, 5, 10, and 20 mg/kg) and morphine (0, 5, 7.5, and 10 mg/kg). Locomotor activity data were simultaneously obtained by measuring distance moved during all different CPP phases and unconditioned locomotor activity, behavioral sensitization and conditioned hyperactivity were measured together with CPP.

Results: (a) Either cocaine or morphine promoted significant CPP at lower doses in C57 than in DBA mice; (b) only drug-trained C57 mice showed a significant CPP compared with the control group; and (c) only C57 mice showed dose-dependent effects of cocaine on CPP. Moreover, there was no relationship between drug-induced CPP and locomotion.

Conclusions: The results demonstrate that C57 and DBA mice differ in their sensitivity to cocaine- and morphine-induced CPP and suggest that the two strains differ in sensitivity to the positive incentive properties of drugs of abuse.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics, Opioid / pharmacology
  • Anesthetics, Local / pharmacology
  • Animals
  • Behavior, Animal / drug effects
  • Behavior, Animal / physiology
  • Cocaine / pharmacology
  • Conditioning, Psychological / drug effects
  • Conditioning, Psychological / physiology*
  • Hyperkinesis / physiopathology
  • Hyperkinesis / psychology
  • Illicit Drugs / pharmacology*
  • Injections, Intraperitoneal
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred DBA
  • Morphine / pharmacology
  • Motor Activity / drug effects
  • Species Specificity

Substances

  • Analgesics, Opioid
  • Anesthetics, Local
  • Illicit Drugs
  • Morphine
  • Cocaine