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| Contemporary behavioral pharmacology: I |
| Sunday, May 27, 2007 |
| 4:00 PM–5:20 PM |
| Ford C |
| Area: BPH |
| Chair: Julie A. Marusich (University of Florida) |
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| Nicotine Self-Administration Using a Multiple Schedule of Intravenous Nicotine and Sucrose Reinforcement in Rats. |
| Domain: Applied Research |
| DUSTIN STAIRS (University of Kentucky), Michael T. Bardo (University of Kentucky) |
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| Abstract: There appears to be a relatively narrow range of contingencies in which intravenous (i.v) infusions of nicotine will maintain responding in rats. The schedule typically used when investigating i.v. nicotine self-administration is a simple fixed-ratio (FR) schedule of reinforcement. The current study investigated whether nicotine would maintain responding in rats using a multiple schedule of i.v. nicotine and sucrose reinforcement. Following training of individual components with each reinforcer, male Sprague Dawley rats (N=6) were placed on a FR5 60-sec timeout multiple schedule of nicotine (0.03 mg/kg/infusion) and sucrose (45 mg pellets) reinforcement. Under the multiple schedule, acute pretreatment with the nicotinic antagonist mecamylamine (0, 1, 2, 4 mg/kg; S.C. 15-min prior to the session) decreased nicotine self-administration specifically. Pretreatments with the dopamine D1 antagonist SCH23390 (0, 2.5, 5.0, 10 ?g/kg; S.C. 25 min prior to the session) also decreased nicotine self-administration specifically. Extinction of the individual nicotine and sucrose components resulted in decreases on the appropriate lever during each component under extinction. The results from this study indicate that i.v. nicotine will maintain responding under a multiple schedule. This procedure may also be useful when studying the specific effects of drugs on nicotine self-administration. Supported by USPHS grant DA13519. |
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| An Examination of the Behavioral Time Course of Cocaine in Pigeons. |
| Domain: Applied Research |
| JULIE A. MARUSICH (University of Florida), Marc N. Branch (University of Florida) |
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| Abstract: Although past research has examined the time course of plasma levels of cocaine in a variety of species, the time course of behavioral effects of cocaine has not been carefully described for any species. Five pigeons were exposed to a multiple Fixed Interval 10 min Fixed Ratio 30 (FI 10’ FR 30) schedule of food presentation, with each component presented 10 times per session, therefore sessions lasted approximately 2 hrs. Effects of acute cocaine administration revealed that the potency half-life (time for the median effective dose to double) of cocaine was consistently longer in the FR component than in the FI component (100 min v. 60 min). Exposure to chronic (i.e., daily) cocaine administration led to tolerance that was characterized by the effects of rate-decreasing doses diminishing earlier in the session compared to acute administration, while formerly rate-increasing doses resulted in rates similar to those under the saline-vehicle control. |
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| The Effects of Fixed Interval and Fixed Ratio Schedules on the Development of Tolerance to Cocaine. |
| Domain: Applied Research |
| MATTHEW T WEAVER (University of Florida), Marc N. Branch (University of Florida) |
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| Abstract: Previous research has shown that tolerance to effects of cocaine depends on fixed-ratio (FR) parameters, but not on fixed-interval (FI) parameters. Six experimentally naive White Carneau pigeons were studied daily under a 4-component multiple schedule that included FR10, FR100, and two FI schedules that were matched to subject’s mean inter-reinforcement times for the aforementioned FR schedules. Once behavior was stable, the pigeons were exposed to various doses of cocaine, with administrations spaced by a week. This Pre-Chronic dose regimen revealed dose-dependent decreases in responding for all subjects. Next a rate-decreasing dose was given before every session, and following the first 30 days of this regimen other doses were tested once per week. The Post-Chronic dose-response functions evidenced tolerance regardless of schedule parameter, or schedule type. The FI schedules are to be removed and subsequent dose-effect assessments with the remaining FR schedules still in force will determine the influence of Fixed-Interval schedules on the pattern of tolerance across schedule parameters. |
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| Effects of Nicotine on Lever Pressing in Rats: Light, Dark, and Food Production. |
| Domain: Applied Research |
| BETHANY R. RAIFF (University of Florida), Jesse Dallery (University of Florida) |
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| Abstract: Several findings suggest that a visual stimulus is needed to maintain nicotine self-administration. Nicotine, in this case, is presumed to function as an establishing operation for responding maintained by the visual stimulus. It is not clear, however, whether nicotine would result in the same pattern of responding with systemic injections of nicotine, without any history of lever pressing or a history of pairing the stimuli with primary reinforcers. The present experiment consisted of 3 phases, where rats (n=6) could press an active lever to produce light (Phase 1), dark (Phase 2), or food, with no additional stimulus changes (Phase 3). In all 3 Phases, an ABA design was used. During the B condition, presession injections of 0.3 mg/kg nicotine were administered. When nicotine affected responding, it produced a nonselective increase in lever pressing on both active and inactive levers relative to baseline. Time course analyses revealed that increases in responding remained present during the entire 60-min session. Furthermore, food was the only consequence that reliably maintained higher response rates on the active lever, suggesting that light and dark production were not serving as primary reinforcers. Experiments using rate of lever pressing as the dependent measure need to consider these direct, systemic effects of nicotine. |
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