Document Detail

Timing and space usage are disrupted by amphetamine in rats maintained on DRL 24-s and DRL 72-s schedules of reinforcement.
MedLine Citation:
PMID:  19142629     Owner:  NLM     Status:  MEDLINE    
RATIONALE: A differential-reinforcement-of-low-rate schedule (DRL) delivers reinforcement only when the interresponse time (IRT) exceeds a fixed time interval, thereby shaping rats to discriminate the timing of their responses. However, little is known about the motor behavior and location of the rats in the chamber during the IRTs that lead to reinforcement. Although amphetamine is known to disrupt DRL timing behavior, the effects of this drug on non-operant motor behavior during DRL performance has not yet been quantified.
OBJECTIVE: The purpose of this research was to measure the motor behavior (movement trajectories in the horizontal plane and spatial location in the plane) during longer IRTs after either vehicle or amphetamine treatment.
MATERIALS AND METHODS: Experimental chambers were constructed with a force-plate actometer as the floor, and while performing the operant task, the rats' motor behaviors were measured continuously with high temporal and spatial resolution. Separate groups of eight male Sprague-Dawley rats were maintained on either DRL 24-s or DRL 72-s schedules of water reinforcement in 4-h recording sessions.
RESULTS: Analyses of IRT distributions showed that the rats' timing behavior conformed to their respective DRL requirements. In the absence of drug, analysis of motor behavior in pre-reinforcement intervals showed that rats located themselves away from the operandum and exhibited very low levels of movement. Rats exhibited a significant temporal diminution of horizontal movement that reached a minimum 4-8 s before the rats moved to the operandum to execute operant responses. Amphetamine treatment increased locomotion, abolished the temporal movement gradient, and brought the rats closer to the operandum compared to vehicle treatment. Movement changes induced by amphetamine were accompanied by degraded timing behavior.
CONCLUSIONS: Taken together, the data show that DRL training induced rats to locate themselves away from the operandum and to remain nearly motionless during longer IRTs and that amphetamine treatment interfered with this complex of behavioral features.
Stephen C Fowler; Jonathan Pinkston; Elena Vorontsova
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2009-01-14
Journal Detail:
Title:  Psychopharmacology     Volume:  204     ISSN:  1432-2072     ISO Abbreviation:  Psychopharmacology (Berl.)     Publication Date:  2009 Jun 
Date Detail:
Created Date:  2009-04-28     Completed Date:  2009-08-05     Revised Date:  2013-08-01    
Medline Journal Info:
Nlm Unique ID:  7608025     Medline TA:  Psychopharmacology (Berl)     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  213-25     Citation Subset:  IM    
Department of Pharmacology and Toxicology, University of Kansas, 5064 Malott Hall, 1251 Wescoe Hall Drive, Lawrence, KS 66045-2505, USA.
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MeSH Terms
Central Nervous System Stimulants / pharmacology*
Conditioning, Operant / drug effects*
Dextroamphetamine / pharmacology*
Motor Activity / drug effects
Rats, Sprague-Dawley
Reinforcement Schedule
Stereotyped Behavior / drug effects
Grant Support
Reg. No./Substance:
0/Central Nervous System Stimulants; 51-64-9/Dextroamphetamine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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