A concurrently available nondrug reinforcer prevents the acquisition or decreases the maintenance of cocaine-reinforced behavior.
Lever-pressing responses of 55 rats were reinforced with IV-delivered cocaine (0.2 mg/kg) or saline under conditions of continuous access for 15 24-h sessions. The rats also responded on tongue-operated drinking devices for deliveries of a 3% (w/v) glucose + 0.125% (w/v) saccharin (G+S) solution or water. The effects of removing these substances on behavior maintained by G+S, water, cocaine, or saline were compared in 11 groups. Terminating cocaine access produced a decrease in G+S drinking and an increase in food and water intake. In contrast, a group of rats that did not initially self-administer G+S showed increases in G+S drinking when cocaine was removed, and G+S-maintained responding persisted when cocaine was reinstated. Substitution of water for G+S produced a nearly two-fold increase in cocaine-reinforced behavior but no change in IV-delivered saline self-administration in a control group. A group that did not initially self-administer cocaine increased its infusion rate to over 400 infusions per day as soon as G+S was replaced with water. The effect of presenting cocaine to a group that responded for G+S alone was to decrease G+S intake, but there was only a transient decrease in water intake in the control group. Likewise, presentation of G+S to a group of rats self-administering cocaine resulted in a decrease in infusions, but saline infusions did not change in a control group. Generally, there was an increase in food and water intake during cocaine removal, but food and water intake did not vary systematically with the removal or presentation of G+S.(ABSTRACT TRUNCATED AT 250 WORDS)
Carroll
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ME
Psychiatry Department, University of Minnesota Medical School, Minneapolis 55455.
Lac
S T
ST
Nygaard
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SL
D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D002149:Energy Intake / Q000187:drug effects; D007262:Infusions, Intravenous; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012054:Reinforcement, Psychology; D012646:Self Administration
D003042:Cocaine