Document Detail

Methadone and feeding: sources of differences between home cage and operant chamber assessment procedures.
MedLine Citation:
PMID:  7816865     Owner:  NLM     Status:  MEDLINE    
Methadone administration is reported to increase food intake in studies examining free feeding and to decrease food reinforced operant responding. In light of this apparent paradox, the present study evaluated methadone's effects on food reinforced operant responding under conditions more typical of free feeding studies than operant studies. The effect of methadone (5 mg/kg) on food intake was examined in rats maintained at 100% of their free feeding weights. Methadone did not increase food intake with food available under a fixed ratio 1 (FR 1) reinforcement schedule. Methadone did not alter response rate when each lever press produced a larger reinforcer (225 mg as opposed to 45 mg), but did increase food intake. When response requirements were changed from lever pressing to interruption of an infrared beam, increases in food intake following methadone administration were observed. Thus, the differences between methadone's effects on free feeding vs. operant chamber food intake may be due to procedural factors such as magnitude of reinforcement and response requirements.
J M Rudski; D W Schaal; T Thompson; J Cleary; C J Billington; A S Levine
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Pharmacology, biochemistry, and behavior     Volume:  49     ISSN:  0091-3057     ISO Abbreviation:  Pharmacol. Biochem. Behav.     Publication Date:  1994 Sep 
Date Detail:
Created Date:  1995-02-07     Completed Date:  1995-02-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0367050     Medline TA:  Pharmacol Biochem Behav     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  143-6     Citation Subset:  IM    
Research Service, VA Medical Center, Minneapolis, MN 55417.
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MeSH Terms
Conditioning, Operant / drug effects*
Eating / drug effects*
Methadone / pharmacology*
Rats, Sprague-Dawley
Reinforcement Schedule
Reg. No./Substance:

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