These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


PUBMED FOR HANDHELDS

Search MEDLINE/PubMed


  • Title: History of cocaine self-administration alters morphine reinforcement in the rat.
    Author: Mierzejewski P, Stefanski R, Bienkowski P, Kostowski W.
    Journal: Eur J Pharmacol; 2007 May 07; 562(1-2):77-81. PubMed ID: 17336286.
    Abstract:
    It has been shown repeatedly that cocaine pre-exposure may sensitise neurochemical and behavioural responses to opioid drugs. The aim of the present study was to investigate effects of a prior history of cocaine self-administration on morphine reinforcement in the rat. Male Sprague-Dawley rats were allowed to acquire intravenous cocaine self-administration (0.3 mg/kg/infusion) for 20 days. When operant responding for cocaine had stabilised, morphine was introduced instead of cocaine in the next self-administration session. One group of cocaine-exposed rats was allowed to respond for 0.56 mg/kg/infusion of morphine (i.e. the dose which was willingly self-administered by drug-naive controls). The second group was allowed to respond for 0.056 mg/kg/infusion of morphine (i.e. the dose which did not maintain self-administration behaviour in the drug-naive rats). The subjects with the history of cocaine self-administration, in contrast to the drug-naive group, did not maintain operant responding for 0.56 mg/kg/infusion of morphine. These rats easily self-administered the ten times lower dose of the opioid (0.056 mg/kg/infusion). An opioid receptor antagonist, naltrexone (1 mg/kg i.p.) restored the positive reinforcing properties of the higher dose of morphine in the cocaine-exposed rats. Concluding, the present results suggest that prior history of cocaine self-administration sensitises rats to the positive reinforcing properties of morphine.
    [Abstract] [Full Text] [Related] [New Search]