Modulation of Ethanol Withdrawal–Induced Anxiety-Like Behavior During Later Withdrawals by Treatment of Early Withdrawals With Benzodiazepine/γ-Aminobutyric Acid Ligands

One of the important features of ethanol exposure in humans is its cyclical nature, whereby alcoholics undergo repeated cycles of intoxication and withdrawal over years (Ballenger and Post, 1978; Brown et al., 1988; Malcolm et al., 2000). Most animal studies modeling ethanol withdrawal entail a single cycle of ethanol treatment and withdrawal and do not reflect its cyclical aspect as observed in humans. The few studies that have been conducted with repeated-cycle models of ethanol withdrawal demonstrate that repeated cycles of treatment and withdrawal can significantly exacerbate seizure symptoms (e.g., Becker and Hale, 1993; McCown and Breese, 1990) and that in some models, such effects may be persistent (Kokka et al., 1993; McCown and Breese, 1990). Furthermore, psychological/emotional withdrawal symptoms such as anxiety may also worsen in the repeated-cycle model (Overstreet et al., 2002, 2003) or in the related chronic intermittent ethanol model (Cagetti et al., 2003). Anxiety is a prominent and common symptom of withdrawal from chronic ethanol in humans (Koob and Le Moal, 1997; Meyer, 1986; Naranjo and Sellers, 1985) and animals (Baldwin et al., 1991; Criswell and Breese, 1993; File et al., 1989; Knapp et al., 1998; Moy et al., 1997, 2000). Anxiety states, including those arising during acute or protracted withdrawal periods, may be precipitating factors in alcoholic relapse (Driessen et al., 2001; Sinha, 2001). An understanding of the conditions in which anxiety arises is important in delineating its neurochemical mechanisms and in developing ameliorative treatments. Given the cyclical nature of ethanol withdrawal as encountered in the clinical setting, meaningful attempts to model and to pharmacologically manipulate ethanol withdrawal–associated anxiety should incorporate cycled ethanol treatments. The studies reported herein examined the pharmacology of social interaction behavior—an established model of anxiety (File et al., 1989, 1993, 1996, 1999; Overstreet et al., 2003)—in rats exposed to repeated cycles of ethanol treatment and withdrawal (Overstreet et al., 2002). Based in part on hypotheses of underactive γ-aminobutyric acid (GABA) systems during ethanol withdrawal (e.g., Allan and Harris, 1987; Crews et al., 1996; Frye et al., 1986), the current studies were conducted primarily to examine benzodiazepine (BZD)–GABAergic influences on this novel effect of cycling on anxiety-like behavior. Drugs predicted to mitigate withdrawal symptoms based on their reported ability to enhance GABA activity via actions including BZD receptor stimulation and neurosteroid receptor stimulation were chosen. Flumazenil, generally considered a BZD receptor antagonist, was also tested based on previous work demonstrating a paradoxical anxiolytic action during withdrawal from other chronic ethanol treatment protocols (e.g., Criswell and Breese, 1993; Knapp et al., 2004; Moy et al., 1997, 2000). Importantly, some groups were specifically chosen to receive drug treatments only during the first two withdrawals of the three-withdrawal protocol. Therefore, behavioral testing in these animals was conducted in a drug-free state. Because other agents known to reduce anxiety-like symptoms in alcohol-withdrawn rats (Knapp et al., 2004) also counteract the anxiety when given as pretreatments (Overstreet et al., 2003, 2004), it was anticipated that BZD-GABA receptor modulating ligands such as flumazenil and the BZD receptor agonist diazepam would counteract ethanol withdrawal–induced anxiety-like behavior in rats subjected to multiple cycles of ethanol exposure.