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| Behavioral Mechanisms of Tolerance to the Effects of Cocaine |
| Saturday, May 29, 2004 |
| 3:00 PM–3:50 PM |
| Beacon E |
| Area: BPH |
| Chair: Marc N. Branch (University of Florida) |
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| Interactions Between Cocaine Sensitization and Tolerance |
| Domain: Applied Research |
| JONATHAN W. PINKSTON (University of Florida), Marc N. Branch (University of Florida) |
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| Abstract: Repeated cocaine exposure may result in sensitization to its effects on locomotor activity. In contrast, tolerance is the usual result when repeated cocaine exposure is examined on behavior under the control of operant contingencies. Previous research has demonstrated increased sensitivity to cocaine's effects on the locomotion of pigeons; however, this sensitivity was eliminated when contingencies were arranged for key pecking. In order to replicate and extend previous findings, the present experiment provided a within-subject comparison of pigeons’ locomotor activity in the context of other behavior that was under explicit schedule control and in the absence of such a context by employing a multiple fixed-ratio extinction schedule. The results showed that after repeated exposure cocaine increased locomotor activity more, if at all, during the extinction component than during the fixed-ratio component. Sensitization of locomotor activity was evident in the behavior of most subjects during the extinction component, but not during the fixed-ratio component. Additionally, tolerance developed to cocaine’s effects on key pecking in the fixed-ratio component. The effects, thus, replicated prior research in a within-subject design. These results suggest an interaction between cocaine’s effects on locomotor activity and the contingencies in place for other responses. |
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| Cocaine Tolerance: Two Variations of FI and FR Values in a Conjunctive Schedule |
| Domain: Applied Research |
| JIN HO YOON (University of Florida), Marc N. Branch (University of Florida) |
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| Abstract: The current set of experiments examined the effects of cocaine on responding under conjunctive FI FR schedules of food reinforcement. Twelve food-deprived pigeons served as subjects. In Experiment 1, subjects were exposed to a three-component multiple FI 10 FI 30 s FI 120 s schedule of reinforcement with a conjunctive FR 5 requirement attached to each interval requirement. The results of Experiment 1 showed FI-parameter independent tolerance in 5 out of 6 subjects. Experiment 2 expanded on Experiment 1 and examined the effects of manipulating the conjunctive FR value across three different levels while keeping the FI requirement constant at 120 s. |
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