Further Characterization of Binge-like Drinking in Sardinian Alcohol-Preferring Rats Exposed to an Unpredictable Schedule of Limited Access to Multiple Alcohol Concentrations

This paper represents an update - with respect to the previous Volterra meeting - on the set up, characterization, and validation of a novel and unique experimental procedure of alcohol drinking capable of promoting exceptionally high intakes of alcohol in Sardinian alcohol-preferring (sP) rats (one of the few rat lines selectively bred worldwide for excessive alcohol consumption). sP rats were exposed to the 4-bottle "alcohol (10%, 20%, and 30%, v/v) vs water" choice regimen during one of the 12 hours of the dark phase of the daily light/dark cycle; the time of alcohol exposure was changed daily under a semi-random order and was unpredictable to rats. Alcohol intake was found to be highly positively correlated (r=0.984, P<0.0001) with the time of alcohol exposure and ranged from an average of approximately 0.7 g/kg (drinking session occurring during the 1st hour of the dark phase) to an average of approximately 2.2 g/kg (drinking session occurring during the 12th hour of the dark phase). Alcohol drinking during the 12th hour of the dark phase resulted in (a) blood alcohol levels averaging approximately 100 mg% and (b) severe signs of alcohol intoxication (e.g., markedly impaired performance at a Rota-Rod task). These results demonstrate that unpredictable, limited access to multiple alcohol concentrations may result in exceptionally high intakes of alcohol in sP rats. A progressively increasing emotional "distress" associated to the rats' expectation of alcohol might be the neurobiological basis of this behavior. Supported by NIAAA-funded "Integrative Neuroscience Initiative on Alcoholism" (INIA-Stress) Consortium.