CONCURRENT POSITIVE AND NEGATIVE GOALBOX EVENTS PRODUCE RUNWAY BEHAVIORS COMPARABLE TO THOSE OF COCAINE-REINFORCED RATS

Rats traversing a straight-alley for reinforcing stimuli typically exh ibit faster running times as training proceeds. In previous work from this laboratory, animals running for a reinforcement consisting of int ravenous infusions of cocaine, unexpectedly demonstrated a progressive increased time to enter the goalbox over trials. Closer observation r evealed that the animals were exhibiting a unique retreat behavior (i. e., stopping their forward advance toward the goalbox and returning to ward the startbox). It was hypothesized that the retreat behavior refl ected an inherent conflict that originated from concurrent positive an d negative associations with the goalbox. Such associations were attri buted to cocaine's dual and well documented reinforcing and anxiogenic effects. To test this idea, the present study compared the runway beh avior of animals that concurrently received food and mild foot shock i n the goalbox to the behavior of other animals running for cocaine. Re sults demonstrated that food + shock reinforced animals took longer to enter the goalbox and made more retreats than a control group that re ceived only food in the goalbox. Both these effects were reversed by p retreatment with the anticonflict, anxiolytic drug, diazepam. The beha vior pattern of animals that received the combination of food and foot shock was found to strongly resemble that of IV cocaine-reinforced rat s, a result consistent with the notion that chronic cocaine administra tion has both positive and negative consequences. (C) 1997 Elsevier Sc ience Inc.