Acute tolerance to alcohol effects on inhibitory and activational mechanisms of behavioral control

Objective: Acute alcohol tolerance refers to the observation of reduced impairment at a given blood alcohol concentration (BAC) on the descending versus ascending limb of the blood alcohol curve. Psychomotor performance measures used in human studies of alcohol tolerance provide reliable assessments of tolerance but do not identify specific mechanisms involved in the re-establishment of control, and little is known about how acute tolerance is expressed in terms of changes in fundamental mechanisms that regulate and control behavior. This study examined the expression of acute alcohol tolerance to impaired behavioral control in terms of changes in a drinker's ability to activate and inhibit behavioral responses as BAC ascended and declined following a dose. Method: Twenty social drinkers performed a cued go/ no-go task that measured behavioral control after receiving a moderate dose (0.65 g/kg) of alcohol and a placebo. The development of acute tolerance was measured by testing behavioral control twice: once during the ascending phase and again at comparable BACs during the descending phase of the blood alcohol curve. Results: Inhibitory and activational aspects of behavioral control both were impaired by alcohol. Acute tolerance developed to the impaired activation but not to the impaired inhibition of behavior. Conclusions: The results highlight the importance of considering behavioral requirements when testing for the development of acute tolerance under a dose of alcohol. By modeling behavioral control as the net effect of countervailing activational and inhibitory influences, the study suggests that fundamental mechanisms of control might not display uniform tolerance development.