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| Ethanol Self-Administration |
| Monday, May 30, 2005 |
| 1:30 PM–2:50 PM |
| Lake Ontario (8th floor) |
| Area: BPH; Domain: Basic Research |
| Chair: Amy Odum (Utah State University) |
| Abstract: This symposium will examine reinforcement parameters that affect ethanol self-administration. The first paper by Jimenez-Gomez and Shahan will describe how the resistance to change of ethanol self-administration in rats is affected by behavioral and pharmacological disruptors. The second paper by Fox and Reilly will report data regarding the effects of work requirement on ethanol polydipsia in rats. The third paper by Flory and Woods will describe the effects of dose and infusion speed on intravenous ethanol self-administration in rhesus monkeys. In the fourth paper, Martinetti and colleagues will examine matching functions in alcohol-preferring, non-preferring, and randomly bred rats. |
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| Resistance to Change of Ethanol Self-Administration: Effects of Behavioral and Pharmacological Disruptors |
| CORINA JIMENEZ-GOMEZ (Utah State University), Timothy A. Shahan (Utah State University) |
| Abstract: Drug self-administration has proven to be an adequate model for assessing variables that contribute to the maintenance of drug taking. The present experiment is concerned with the persistence of drug self-administration, a defining characteristic of drug dependence and abuse. Findings from studies of the resistance to change of food-maintained responding may contribute to a better understanding of the persistence of drug abuse and dependence. Using an animal model of alcohol self-administration, this study evaluates the effects of rate of reinforcement on the persistence of ethanol self-administration in rats in the face of behavioral (i.e., extinction) and pharmacological (i.e., naltrexone) disruptors. Four naïve Long Evans rats were trained to respond for a 10% (vol/vol) ethanol solution on a multiple variable-interval (VI) 15-s VI 45-s schedule of reinforcement. Baseline response rates were higher for the component that provided higher rates of ethanol delivery. Consistent with behavioral momentum theory, responding was more resistant to extinction in the component with higher rates of ethanol delivery. Disruption with naltrexone (1.0, 3.0, 10.0 mg/kg, sc), injected one hour before the session, is currently being conducted. Results will be discussed in terms of the utility of behavioral momentum theory in understanding the persistence of drug taking. |
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| Periodic Food Delivery Induces Greater Ethanol Polydispia When Rats Have to Work for Food |
| ANDREW T. FOX (Central Michigan University), Mark P. Reilly (Central Michigan University) |
| Abstract: The following study was undertaken to determine the relative contributions of effort and interreinforcement interval in determining the level of ethanol polydipsia in rats. Rats were trained to lever press for food under ratio schedules. Two procedures were employed. In the first, rats lever pressed for food according to a modified progressive ratio schedule that increased geometrically every ten reinforcers or two minutes. In the second, rats lever pressed for food according to a fixed ratio schedule that increased geometrically across sessions. In both procedures, a liquid delivery spout containing a ten percent solution of ethanol was freely available during sessions. Licks on the spout were recorded. After training on these procedures, half of the rats were yoked so that food was delivered independently of their behavior and according to the rate of food earned by the master rats. Preliminary results indicate a lawful relationship between inter-food interval and ethanol consumption. Ethanol consumption was reduced when rats received response-independent food compared to response-dependent food. Results will be discussed in terms of the importance of work in predicting polydipsia and also how the scheduling of alternative reinforcers affects drug consumption. |
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| The Reinforcing Efficacy of Intravenously Self-Administered Ethanol by Rhesus Monkeys as a Function of Dose and Infusion Speed |
| GRAHAM FLORY (University of Michigan), James H. Woods (University of Michigan) |
| Abstract: It has repeatedly been found that when the dose of orally self-administered ethanol is varied, total session intake remains relatively stable. This has led many to believe that ethanol self-administration is motivated by the attainment of a threshold level of circulating drug in the brain. If this is in fact correct, then animals should orally self-administer the same amount of ethanol as they self-administer intravenously. However, when given the opportunity to intravenously self-administer ethanol, rhesus monkeys will invariably consume 300-400% more ethanol than they will by the oral route. By examining a sufficiently broad range of doses, it has become apparent that the attainment of a threshold level of ethanol in the brain is not a necessary component of an animal’s motivation to self-administer it. The differences seen between the oral and intravenous routes of self-administration are simply one of dose, with larger doses engendering greater levels of intake. This phenomenon can be understood by viewing consumption as a measure of reinforcing efficacy, which increases with the more rapid onset of pharmacological effect that characterizes larger drug doses. |
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| Matching Law Analyses of Ethanol and Sucrose Consumption in Alcohol-Preferring (P), Non-Preferring (NP), and Randomly Bred Rats |
| MARGARET P. MARTINETTI (The College of New Jersey), Sally R. Vona (The College of New Jersey), Alison Wichnick (The College of New Jersey), Matthew E. Andrzejewski (University of Wisconsin-Madison) |
| Abstract: Recently, quantitative models of choice have been applied to the study of drug and alcohol consumption. Specifically, the matching law has been used to describe the nature of ethanol as a reinforcer. This talk will include data from several studies conducted using the matching law to assess relative consumption of differing ethanol and sucrose solutions in a limited-access, two-bottle choice procedure. Our earliest work examined relative consumption of unsweetened ethanol solutions in Sprague-Dawley rats. The ratio of ethanol concentrations fairly reliably predicted relative consumption of those solutions for most of the animals, and g/kg ethanol consumption was positively correlated with sensitivity to the ratio of concentrations. In a second study, P and NP rats were given access to differing ethanol solutions in the same paradigm and relative consumption was assessed as a function of relative ethanol concentration.In that study, P rats consistently overmatched, showing high sensitivities, while NP data were variable. Current research to be presented at the meeting includes two additional matching law studies investigating 1) differing concentrations of sucrose and 2) saccharin-sweetened ethanol solutions containing differing amounts of ethanol. Both of these studies will use P, NP, and Wistar rats. |
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