Ivana Grakalic1, Charles W Schindler, Michael H Baumann, Kenner C Rice, Anthony L Riley. 1. Preclinical Pharmacology Section, Behavioral Neuroscience Branch, DHHS/NIH/NIDA Intramural Research Program, National Institute on Drug Abuse, 5500 Nathan Shock Drive, Baltimore, MD, 21224, USA. igrakalic@intra.nida.nih.gov
Abstract
RATIONALE: There is a direct relationship between hypothalamic-pituitary-adrenal axis (HPA) reactivity and susceptibility to drug use in outbred rats. Specifically, manipulations that increase or decrease HPA activity also increase or decrease drug intake, respectively. Interestingly, this relationship has not been established in the inbred Fischer (F344) and Lewis (LEW) rat strains that are often used as animal models of susceptibility to drug use. OBJECTIVE: The present study investigated the effects of manipulations known to affect HPA activity on morphine-induced conditioned place preference (CPP) in male LEW, F344, and Sprague-Dawley (SD) rats. MATERIALS AND METHODS: In experiment 1, animals were exposed to an injection of methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) and 2-h restraint stress prior to the conditioning of a morphine-induced place preference (1, 4, or 10 mg/kg subcutaneous). In experiment 2, animals were chronically exposed to corticotropin-releasing hormone type 1 receptor antagonist, antalarmin, prior to CPP training. The effects of DMCM/restraint and antalarmin on corticosterone levels were examined in experiments 3 and 4. RESULTS: In outbred rats, DMCM/restraint increased both HPA activity and morphine-induced CPP, while antalarmin decreased CPP and produced a slight, but nonsignificant, decrease in corticosterone levels. In the inbred rats, however, DMCM/restraint increased plasma corticosterone yet decreased place preferences in the LEW strain, and antalarmin treatment decreased plasma corticosterone but increased place preferences in the F344 strain. CONCLUSIONS: These data suggest that the relationship between stress and drug use may be nonmonotonic. The use of these inbred strains in genetic analysis of drug addiction may require reexamination.
RATIONALE: There is a direct relationship between hypothalamic-pituitary-adrenal axis (HPA) reactivity and susceptibility to drug use in outbred rats. Specifically, manipulations that increase or decrease HPA activity also increase or decrease drug intake, respectively. Interestingly, this relationship has not been established in the inbred Fischer (F344) and Lewis (LEW) rat strains that are often used as animal models of susceptibility to drug use. OBJECTIVE: The present study investigated the effects of manipulations known to affect HPA activity on morphine-induced conditioned place preference (CPP) in male LEW, F344, and Sprague-Dawley (SD) rats. MATERIALS AND METHODS: In experiment 1, animals were exposed to an injection of methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) and 2-h restraint stress prior to the conditioning of a morphine-induced place preference (1, 4, or 10 mg/kg subcutaneous). In experiment 2, animals were chronically exposed to corticotropin-releasing hormone type 1 receptor antagonist, antalarmin, prior to CPP training. The effects of DMCM/restraint and antalarmin on corticosterone levels were examined in experiments 3 and 4. RESULTS: In outbred rats, DMCM/restraint increased both HPA activity and morphine-induced CPP, while antalarmin decreased CPP and produced a slight, but nonsignificant, decrease in corticosterone levels. In the inbred rats, however, DMCM/restraint increased plasma corticosterone yet decreased place preferences in the LEW strain, and antalarmin treatment decreased plasma corticosterone but increased place preferences in the F344 strain. CONCLUSIONS: These data suggest that the relationship between stress and drug use may be nonmonotonic. The use of these inbred strains in genetic analysis of drug addiction may require reexamination.
Authors: Javier Navarro-Zaragoza; Cristina Núñez; Jessica Ruiz-Medina; M Luisa Laorden; Olga Valverde; M Victoria Milanés Journal: Br J Pharmacol Date: 2011-02 Impact factor: 8.739
Authors: A Higuera-Matas; G L Montoya; S M Coria; M Miguéns; C García-Lecumberri; E Ambrosio Journal: Curr Neuropharmacol Date: 2011-03 Impact factor: 7.363