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| Quantitative Analyses in Behavioral Pharmacology: Studies of Choice, Behavioral Momentum, and Self-Control |
| Sunday, May 27, 2007 |
| 9:00 AM–10:20 AM |
| Ford C |
| Area: BPH; Domain: Basic Research |
| Chair: Tammy Wade-Galuska (University of Michigan) |
| Abstract: This symposium highlights recent advances in the behavioral assays and quantitative analyses being used in behavioral pharmacology research. In the first presentation, McFeron and colleagues will discuss how the behavioral momentum paradigm can be employed to assess the reinforcing functions of cocaine in rats. Resistance-to-change assays ultimately may be useful in studying the persistence of illicit drug-taking behavior in humans. In the second presentation, Slezak and Anderson will report their use of a delay discounting paradigm to study the effects of acute and chronic methylphenidate on impulsivity in spontaneously hypertensive rats. Results show that methylphenidate, a stimulant used to treat attention-deficit/hyperactivity disorder, increases self-control choice. In the third presentation, Wade-Galuska and colleagues assess the economic relation between a stimulant and opioid drug using a drug self-administration assay in rhesus monkeys. Cocaine and remifentanil appear to be economic substitutes; increasing the price of one drug leads to increased consumption of the other. Finally, Koffarnus and Woods will describe how the matching law can be employed to study preference between self-administered drugs in rhesus monkeys. Specifically, they will show that monkeys are sensitive to the obtained rate of reinforcement and the drug type and that preference for drug type and/or dose is indexed by the bias parameter of the generalized matching law. |
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| Behavioral Momentum of Cocaine Self-Administration. |
| STACEY MCFERON (Utah State University), Corina Jimenez-Gomez (Utah State University), Timothy A. Slocum (Utah State University) |
| Abstract: Studies on the behavioral momentum of food-maintained responding have found that responding in the presence of a stimulus associated with a higher rate of reinforcement is more resistant to change than responding in the presence of a stimulus associated with a lower rate of reinforcement. Recent experiments have extended the study of behavioral momentum to alcohol-maintained responding. The present experiment assessed the persistence of cocaine-maintained behavior in a two-component multiple schedule with rats. In one component, lever-presses were maintained by a lower rate of intravenous cocaine infusions, while in a second component, lever-presses were maintained by a higher rate of intravenous cocaine infusions. Following a stable baseline of response rate and infusion rate, cocaine was removed for 5 consecutive sessions. During this extinction period, responding in the presence of the stimuli previously associated with a high-rate of cocaine infusions was more resistant to change than responding in the presence of stimuli associated with a low-rate of cocaine infusions. This result occurred despite the fact that response rates in the two components were approximately equal during baseline. These findings suggest behavioral momentum theory may provide a useful framework for understanding the persistence of drug-taking in the presence of drug-associated stimuli. |
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| Effects of Acute and Repeated Administration of Methylphenidate on Delay Discounting in Spontaneously Hypertensive Rats (SHR). |
| JONATHAN M. SLEZAK (West Virginia University), Karen G. Anderson (West Virginia University) |
| Abstract: Impulsive choice (e.g., preference for a small, immediate reinforcer, over a larger, delayed reinforcer) has been suggested to be a prominent characteristic of attention-deficit/hyperactivity disorder (ADHD). Methylphenidate (MPH), a stimulant drug, is a common pharmacological treatment of ADHD. To assess effects of acute and repeatedly administered MPH on impulsive choice in an animal model of ADHD, SHR (n = 8) were evaluated in a delay-discounting paradigm. Rats chose (a single response on one of two levers) between one food pellet delivered immediately and three food pellets presented after a delay, which increased systematically across the session from 0, 2, 4, 8 and 16 s. Preference for the larger reinforcer decreased as the delay to its presentation increased. Acute administration of MPH (1.0, 3.0, 5.6, 10.0 mg/kg, i.p.) dose-dependently increased the number of larger-reinforcer (self-control) choices for all subjects. Individual differences in choice, however, were observed following repeated administration of MPH. The present results in this animal model of ADHD are consistent with those from other rat strains that show stimulant drugs increase self-control choice. |
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| A Behavioral Economic Analysis of Cocaine and Remifentanil Self-Administration in Rhesus Monkeys. |
| TAMMY WADE-GALUSKA (University of Michigan), Gail Winger (University of Michigan), James H. Woods (University of Michigan) |
| Abstract: Demand-curve analyses describe changes in the consumption of a commodity as a function of price. This analysis can be used to assess the relative reinforcing effectiveness of drugs, potentially providing useful information about polydrug abuse in humans. In the first experiment, demand-function analysis was used to quantify the reinforcing effectiveness of cocaine and remifentanil in six rhesus monkeys. Only one drug was available for self-administration across increasing response requirements. Own-price elasticity refers to the rate at which a single drug decreases as a function of increases in its price (response requirement). We found that 0.03 mg/kg cocaine and 0.0003 mg/kg remifentanil had comparable own-price elasticity, with remifentanil being slightly more inelastic for some monkeys. In the second experiment, five monkeys could choose between cocaine (0.03 mg/kg) and remifentanil (0.0003 mg/kg) by responding on one of two levers. Cross-price elasticity refers to how consumption of one drug at a constant price changes as a function of the price of a concurrently available alternative drug. The price of cocaine and remifentanil was manipulated by altering the response requirement associated with each. We found that cocaine and remifentanil are substitutable commodities. As the price of cocaine increased, monkeys self-administered more remifentanil, and vice-versa. |
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| The Generalized Matching Law as a Quantitative Measure of Relative Choice among Cocaine, Remifentanil, and Methohexital in Rhesus Monkeys. |
| MIKHAIL KOFFARNUS (University of Michigan), James H. Woods (University of Michigan) |
| Abstract: Matching law procedures have been used extensively to describe differential behavior allocation with two response options present, including conditions where the two response options are paired with qualitatively different reinforcers. The current study expands on these findings to compare drugs of abuse from different classes as reinforcers. Three rhesus monkeys were trained to respond on concurrent RI schedules (range RI 3 min to RI 15 min) with contingent delivery of various combinations of cocaine, remifentanil (short-acting opioid), methohexital (short-acting anesthetic), and saline vehicle. Rates of responding matched to the schedule contingencies with all drug combinations except when saline was included as one option. Levels of undermatching were similar to previous studies. Monkeys also showed a bias toward larger doses of drugs over smaller ones. The results demonstrate that the matching law describes the behavior of monkeys responding on concurrent RI schedules with qualitatively different drugs as reinforcers, and that matching law procedures can be used to quantify relative bias for a particular drug/dose combination over another. |
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