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.
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 DBAmice 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 DBAmice; (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 DBAmice 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.
Authors: R K McNamara; B Levant; B Taylor; R Ahlbrand; Y Liu; J R Sullivan; K Stanford; N M Richtand Journal: Neuroscience Date: 2006-08-28 Impact factor: 3.590
Authors: George R Uhl; Tomas Drgon; Catherine Johnson; Oluwatosin O Fatusin; Qing-Rong Liu; Carlo Contoreggi; Chuan-Yun Li; Kari Buck; John Crabbe Journal: Biochem Pharmacol Date: 2007-07-25 Impact factor: 5.858