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| International Paper Session - Contemporary behavioral pharmacology: II |
| Monday, May 28, 2007 |
| 1:30 PM–2:50 PM |
| Ford C |
| Area: BPH |
| Chair: Jonathan W. Pinkston (University of Kansas) |
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| Amphetamine-Induced Increases in Fixed-Ratio Responding Following the Cessation of Focused Stereotype. |
| Domain: Applied Research |
| JONATHAN W. PINKSTON (University of Kansas), Stephen Fowler (University of Kansas) |
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| Abstract: Previous research has demonstrated that middle to high doses of amphetamine (AMP) decrease operant behavior under fixed-ratio (FR) schedules. As FR schedules typically engender moderate to high response rates, decreases observed under AMP have been taken to support the role of response rate as a determinant of a drug’s effect (e.g., rate-dependency hypothesis). Recent work in our lab, however, has demonstrated that response rate may increase under FR schedules when observed over long sessions. Eight Sprague-Dawley rats were trained to respond on a multiple FR 20 Extinction schedule of water delivery. Daily sessions lasted for four hours. Once responding reached a stable level, 5.0 mg/kg d-amphetamine was administered pre-session every fourth day for 20 days. Tests of the saline vehicle were made in between each AMP administration. As reported previously, repeated AMP administrations induced bouts of repetitive head movements accompanied by little locomotion; additionally, operant behavior was suppressed during these bouts. This period of “focused stereotypy” typically lasted for approximately 1.5 hours. When stereotypy subsided and operant responding resumed, about 2 – 2.5 hours after the beginning of the session, transitory increases in response rate were observed in all rats. Separate control conditions excluded additional deprivation factors and response blocking (i.e. contrast-like effects) as possible causes for these increases. The data suggest that the prevailing notions that AMP decreases fixed-ratio responding are based on the widespread use of much shorter observation sessions (e.g. 1 hour), when the full course of amphetamine’s response is examined increases can be observed. |
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| Scopolamine Effects under a Titrating-Delayed-Non-Matching-to-Sample Procedure: Modulation by Titration Interval. |
| Domain: Applied Research |
| MATTHEW L. PORRITT (Western Michigan University), Alan D. Poling (Western Michigan University) |
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| Abstract: The purpose of the present study was to examine the performance of rats exposed to three variations of a TDNMTP procedure, with the variations defined in terms of the length of the titration interval, and to examine the effects of scopolamine under each variant. Prior studies have reported the effects of scopolamine, an anticholinergic drug known to produce "memory" impairment, in rats performing under non-adjusting procedures. It was of interest to compare the sensitivity of these procedures to the TDNMTP procedures used in the present study. The titrating procedure proved to be a highly sensitive variation of the matching to position assay. |
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| Haloperidol, Different Schedules of Reinforcement, and Anhedonia. |
| Domain: Applied Research |
| CARLOS F. APARICIO (University of Guadalajara, Mexico) |
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| Abstract: The idea that dopamine, particularly in nucleus accumbens, mediates the hedonic properties of reinforcers (i.e., food, water, saccharine), subsist in the field of the neurosciences. Evidence supporting this idea comes from studies showing that the organism under the effects of dopamine antagonists (e.g., haloperidol) quits responding (i.e., pressing a lever) for food reinforcers. After years of debate and experimental test, the anhedonia hypothesis appear no longer tenable as such. The main reason for this is that food reinforcers are to a large extend dopamine-independent, the impairment of food reinforcement by manipulation of dopamine transmission being due to mechanisms other than hedonic devaluation. The present talk will extend the generality of this notion with rats responding under the effects of haloperidol to different schedules of reinforcement. The results will show that suppressive effect of haloperidol on operant responding depends of the type of reinforcer used, the schedule of reinforcement being implemented, and the via (sc or ip) utilized to administrate the drug. |
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| Comparison of the Oral and Intravenous Routes in the Self-Administration of MDMA (‘Ecstasy’) in Rats. |
| Domain: Applied Research |
| LINCOLN S. HELY (Victoria University of Wellington, New Zealand), David N. Harper (Victoria University of Wellington, New Zealand), Maree J. Hunt (Victoria University of Wellington, New Zealand), Susan Schenk (Victoria University of Wellington, New Zealand) |
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| Abstract: Recent studies have produced reliable self-administration of the so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) in rats. This finding suggests that MDMA may share many of the addictive properties common to other prominent CNS stimulants (such as cocaine and amphetamine). The well known abuse potential of the CNS stimulants suggests that MDMA may also prove to be addictive, though anecdotally the drug is not considered to be addictive. Experimental evidence for the addictive properties of MDMA can be derived from experimental manipulations of the self-administration procedure. In humans MDMA is primarily consumed in one or more oral doses, however animal studies have relied upon the IV route of administration in the study of its effects. This research examined the use of the oral route of administration in rats, and compares the effectiveness of the oral route with that of the IV route. A Behavioral Economic analysis was utlized as a way to quantify the differences in reinforcing efficacy of MDMA as a function of the route of administration, but also as a comparison point for studying the addictive potential of MDMA in comparison to other drugs of abuse. |
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