Combining the 1-Adrenergic Receptor Antagonist, Prazosin, with the -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 1-adrenergic receptors with the antagonist, prazosin, decreased alcohol drinking in rats under various conditions. As noradrenergic activation is also regulated by -adrenergic receptors, we now examine the effects of the -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 1, rats were allowed to become alcohol-dependent during 14weeks of ad libitum access to food, water, and 20% alcohol, and the effect of propranolol (5 to 15mg/kg, intraperitoneally [IP]) and prazosin (1 to 2mg/kg, IP) on alcohol intake during withdrawal was assessed. In study 2, the effect of propranolol (5mg/kg, IP) and prazosin (2mg/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 2 drugs was more effective than was treatment with either drug alone. Conclusions Treatment with prazosin+propranolol, or a combination of other centrally active 1- and -adrenergic receptor antagonists, may assist in preventing alcohol relapse in some individuals.