0 145 -6008/00/2403-0278$03.00/0 ALCOHOLISM: CLINICAL AND EXPERIMENTAL RESEARCH Vol. 24, No. 3 March 2000 zy P Rats Develop Physical Dependence on Alcohol Via Voluntary Drinking: Changes in Seizure Thresholds, Anxiety, and Patterns of Alcohol Drinking zy Alexey B. Kampov-Polevoy, Douglas zyxwvut B. Matthews, Lee Gause, A. Leslie Morrow, and David H. Overstreet Background It has been proposed that the alcohol-preferring P rat meets many of the criteria for an animal model of alcoholism. However, the development of alcohol dependence has not been explored in rats that self-administer ethanol for less than 15-20 weeks. The present study investigated the development of physical dependence upon alcohol after 2-6 weeks of voluntary alcohol intake. Changes in bicuculline- induced seizure thresholds, microstructure of alcohol drinking, and anxiety-related behavior were used as indices of alcohol dependence. In addition, we evaluated the microstructure of alcohol drinking associated with the development of physical dependence upon alcohol. Methods: Alcohol (10% ethanol solution) was measured in graduated drinking tubes with both alcohol and water available continuously. Microstructure of alcohol intake was monitored by a computerized drinkometer. Physical dependence upon alcohol was determined by measuring bicuculline-induced seizure thresholds after alcohol withdrawal. Anxiety-related behavior of P rats after alcohol withdrawal was deter- mined by the social interaction and elevated plus maze tests. Results: Initial alcohol intake in the alcohol-preferring P rat was relatively modest (3.9 zyxwv 2 0.4 g/kg/day). Four days of forced alcohol exposure (initiation) followed by 6 weeks of voluntary drinking resulted in an increase of alcohol intake to 5.5 zyxwvuts t 0.2 &@day. Ethanol self-administration for zyxwvu 6 weeks, but not for 2 or 4 weeks, produced a significant reduction (30%; p < 0.05) in bicuculline-induced seizure thresholds during alcohol withdrawal. Alterations in the microstructure of alcohol intake (i.e., 90% increase in the size of alcohol drinking bouts compared to the baseline [p < 0.0011 with no change in bout frequency) were associated with the development of alcohol dependence. Termination of alcohol intake after 6 weeks of voluntary alcohol consumption resulted in increased anxiety according to both the social interaction and elevated plus maze tests. Conclusions: The results of this study indicate that 6 weeks of voluntary alcohol intake are sufficient for the development of physical dependence upon alcohol in the alcohol-preferring P rats as measured by susceptibility to bicuculline-induced seizures. This time is much shorter than the 15-20 weeks reported earlier. Development of physical dependence to alcohol was associated with an increase in daily alcohol intake (40% over the baseline), an increase in alcohol intake during each drinking bout (90% over the baseline), and elevated anxiety during alcohol withdrawal. Key Words: P Rats, Alcohol withdrawal, Bicuculline, Anxiety. HRONIC ALCOHOL CONSUMPTION results in the C development of tolerance and dependence upon al- coho1 in both animals and humans (Sellers and Kalant, 1976). Ethanol dependence may be subdivided into two main aspects: psychological (behavioral) and physical. On From the Bowles Center for Alcohol Studies (A.B.K.-P., D.B.M., L.G., A.L.M., D.H.O.), and the Departments of Psychiatry (A.B.X-P., D.B.M., A.L.M., D.H. zyxwvutsrqpon 0.) and Pharmacology (A.L.M.), University of North Carolina School of Medicine, Chapel Hill, North Carolina. Received for publication September 13, 1999; accepted January 6, 2000. The study was supported by P50 AA11605 and NRSA zyxwvuts AA05519 grants )?om N M . The Prats obtained from the Indiana Alcohol Research Center were supported by P50-AAO7611 from NIAAA. Reprint requests: David H. Overstreet, Ph.D., Bowles Center for Alcohol Studies, CB#7178, 3011 Thurston-Bowles Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7178; Fax: 919-966-5679. Copyright 0 2000 by the Research Society on Alcoholism. 270 the one hand, physical dependence is characterized by the appearance of a large spectrum of symptoms after alcohol removal with autonomic nervous system hyperactivity, such as general rigidity and tremors produced by a neuronal excitation. In animal models of ethanol withdrawal, central nervous system hyperexcitability, after removal of an ethanol-containing diet, has been demonstrated as evi- denced by a significant reduction in bicuculline-induced seizure thresholds ( Devaud et al., 1995). On the other hand, alcohol deprivation in alcohol-dependent individuals results in a negative affective state which is characterized by dysphoria and anxiety in humans and by a reward deficit and enhanced anxiety-like behaviors in laboratory animals (Koob, 1996). Animals withdrawn from ethanol after chronic exposure show increased anxiety-like behavior in the social interaction test (File et al., 1989) and elevated Alcohol Clin Exp Res, Vol24, No 3, 2000: pp 278-284