Document Detail

A role for mu opioid receptors in cocaine-induced activity, sensitization, and reward in the rat.
MedLine Citation:
PMID:  17687547     Owner:  NLM     Status:  MEDLINE    
RATIONALE: Considerable evidence suggests that the endogenous opioid system plays a role in mediating the behavioral effects of psychostimulants. Opioidergic drugs have been shown to have profound effects on cocaine-induced behavioral sensitization and conditioned reward. However, the role specifically of the mu opioid receptor in this regard is unclear as most previous pharmacological studies have used nonselective opioid receptor ligands.
OBJECTIVES: The objective of this series of experiments was to elucidate the role of mu opioid receptors in the behavioral effects of cocaine in the rat.
MATERIALS AND METHODS: Adult male rats were used to assess the effects of the selective mu opioid receptor antagonist D: -Phe-Cys-Tyr-D: -Trp-Arg-Thr-Pen-Thr (CTAP) on acute hyperactivity, locomotor sensitization, and conditioned place preference induced by cocaine. Intracerebroventricular administration of CTAP, 4 microg, was paired with peripheral injections of cocaine, 10-15 mg/kg.
RESULTS: Mu receptor blockade significantly attenuated cocaine-induced hyperactivity, as well as the development of behavioral sensitization. Pretreatment with CTAP also prevented the development of conditioned place preference to cocaine. Administration of CTAP alone had neither effect on locomotor activity nor did it demonstrate aversive or rewarding properties.
CONCLUSIONS: These results suggest that activation of mu opioid receptors by endogenous opioids is an important contributor to cocaine-induced hyperactivity and the development of behavioral sensitization and conditioned reward.
Joseph A Schroeder; Michele Hummel; Alpha D Simpson; Rizwan Sheikh; Avery R Soderman; Ellen M Unterwald
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2007-08-09
Journal Detail:
Title:  Psychopharmacology     Volume:  195     ISSN:  0033-3158     ISO Abbreviation:  Psychopharmacology (Berl.)     Publication Date:  2007 Dec 
Date Detail:
Created Date:  2007-11-01     Completed Date:  2008-02-25     Revised Date:  2014-03-25    
Medline Journal Info:
Nlm Unique ID:  7608025     Medline TA:  Psychopharmacology (Berl)     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  265-72     Citation Subset:  IM    
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MeSH Terms
Analysis of Variance
Behavior, Animal / drug effects*
Cocaine / pharmacology*
Conditioning, Operant / drug effects
Dose-Response Relationship, Drug
Motor Activity / drug effects*
Peptide Fragments
Peptides / administration & dosage,  pharmacology
Rats, Sprague-Dawley
Receptors, Opioid, mu / antagonists & inhibitors,  physiology*
Grant Support
Reg. No./Substance:
0/CTAP octapeptide; 0/Peptide Fragments; 0/Peptides; 0/Receptors, Opioid, mu; 51110-01-1/Somatostatin; I5Y540LHVR/Cocaine

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