Prazosin + Naltrexone Decreases Alcohol Drinking More Effectively Than Does Either Drug Alone in P Rats with a Protracted History of Extensive Voluntary Alcohol Drinking, Dependence, and Multiple Withdrawals

Background Prazosin (PRZ, an α1-adrenergic receptor antagonist) and naltrexone (NTX, a non-specific opioid receptor antagonist) each decrease alcohol drinking when administered to rats selectively-bred for high voluntary alcohol drinking (alcohol-preferring, or “P”), and the combination of PRZ+NTX decreases alcohol drinking more effectively than does either drug alone. Since drug responsiveness can depend on history of alcohol drinking and dependence, we investigated whether various schedules of PRZ and NTX administration, alone or in combination, are effective in decreasing alcohol drinking in male P rats with a history of protracted voluntary alcohol drinking, dependence and repeated withdrawals closely resembling human alcoholism. Methods Male P rats became alcohol-dependent during 1 year of ad libitum 24 h/day access to food, water and 20% alcohol with repetitive temporary alcohol withdrawals. Four sequential studies then addressed effects of oral PRZ (2 mg/kg) and NTX (10 mg/kg), alone or together, on alcohol drinking during: 1) daily alcohol access with daily drug treatment, 2) intermittent alcohol access with daily drug treatment, 3) intermittent alcohol access with occasional drug treatment, and 4) post-deprivation reinstatement of alcohol access. Results The combination of PRZ+NTX consistently suppressed alcohol drinking during daily or intermittent alcohol access conditions and when drug treatment was either daily or occasional. PRZ+NTX was consistently more effective than either drug alone. The reduction in alcohol drinking was not due to sedation, motor effects or malaise. Conclusions Both daily and “as-needed” treatment with PRZ+NTX are highly effective in suppressing daily, intermittent and post-deprivation alcohol drinking in male P rats with a protracted history of alcohol dependence and repeated withdrawals. This drug combination may be especially effective for treating individuals with long histories of heavy alcohol abuse, dependence and repeated relapse, as commonly encountered in clinical practice

Combining the α1-Adrenergic Receptor Antagonist, Prazosin, with the β-Adrenergic Receptor Antagonist, Propranolol, Reduces Alcohol Drinking More Effectively Than Either Drug Alone

Background Evidence suggests that activation of the noradrenergic system may contribute to alcohol drinking in animals and humans. Our previous studies demonstrated that blocking α1-adrenergic receptors with the antagonist, prazosin, decreased alcohol drinking in rats under various conditions. Since noradrenergic activation is also regulated by β-adrenergic receptors, we now examine the effects of the β-adrenergic receptor antagonist, propranolol, alone or in combination with prazosin, on alcohol drinking in rats selectively bred for high voluntary alcohol intake and alcohol preference (P line). Methods Two studies were conducted with male P rats. In study one, rats were allowed to become alcohol-dependent during 14 weeks of ad libitum access to food, water and 20% alcohol and the effect of propranolol (5–15 mg/kg, IP) and prazosin (1–2 mg/kg, IP) on alcohol intake during withdrawal were assessed. In study two, the effect of propranolol (5 mg/kg, IP) and prazosin (2 mg/kg, IP) on alcohol intake following prolonged imposed abstinence was assessed. Results Alcohol drinking following propranolol treatment was variable, but the combination of propranolol + prazosin consistently suppressed alcohol drinking during both alcohol withdrawal and following prolonged imposed abstinence, and the combination of these two drugs was more effective than was treatment with either drug alone. Conclusions Treatment with prazosin + propranolol, or a combination of other centrally active α1- and β-adrenergic receptor antagonists, may assist in preventing alcohol relapse in some individuals

Prazosin Prevents Increased Anxiety Behavior That Occurs in Response to Stress During Alcohol Deprivations

AIMS: Stress-induced anxiety is a risk factor for relapse to alcohol drinking. The aim of this study was to test the hypothesis that the central nervous system (CNS)-active α1-adrenergic receptor antagonist, prazosin, would block the stress-induced increase in anxiety that occurs during alcohol deprivations. METHODS: Selectively bred male alcohol-preferring (P) rats were given three cycles of 5 days of ad libitum voluntary alcohol drinking interrupted by 2 days of alcohol deprivation, with or without 1 h of restraint stress 4 h after the start of each of the first two alcohol deprivation cycles. Prazosin (1.0 or 1.5 mg/kg, IP) or vehicle was administered before each restraint stress. Anxiety-like behavior during alcohol deprivation following the third 5-day cycle of alcohol drinking (7 days after the most recent restraint stress ± prazosin treatment) was measured by performance in an elevated plus-maze and in social approach/avoidance testing. RESULTS: Rats that received constant alcohol access, or alcohol access and deprivations without stress or prazosin treatments in the first two alcohol deprivations did not exhibit augmented anxiety-like behavior during the third deprivation. In contrast, rats that had been stressed during the first two alcohol deprivations exhibited increased anxiety-like behavior (compared with control rats) in both anxiety tests during the third deprivation. Prazosin given before stresses in the first two cycles of alcohol withdrawal prevented increased anxiety-like behavior during the third alcohol deprivation. CONCLUSION: Prazosin treatment before stresses experienced during alcohol deprivations may prevent the increased anxiety during subsequent deprivation/abstinence that is a risk factor for relapse to alcohol drinking. SHORT SUMMARY: Administration of prazosin before stresses during repetitive alcohol deprivations in male alcohol-preferring (P) rats prevents increased anxiety during a subsequent deprivation without further prazosin treatment. Prazosin treatment during repeated alcohol deprivations may prevent the increased anxiety that is a risk factor for relapse to alcohol drinkin