Effects of response cost and unit dose on alcohol self-administration in moderate drinkers.

Alcohol self-administration by nonhumans and alcoholic humans decreases as the response requirement to obtain the drug increases. Also, increases in dose or concentration of alcohol, increase consumption up to a maximum in these populations, after which further increases in dose decrease intake. In the present study, the effects of response cost and dose on alcohol self-administration were investigated in moderate drinkers (12-45 drinks/week). Three male volunteers self-administered alcohol (commercial beer) during 2h sessions twice weekly. Alcohol was available under a fixed-ratio (FR) schedule of reinforcement. Response requirement (FR100-1600) and dose (2 and 4oz of beer) were varied separately across sessions using a within-subjects design. As response cost increased, consumption and overall rates of responding generally changed in an inverted U-shaped manner. Maximal consumption was observed at the 4oz dose. These orderly relations between response cost, dose and alcohol self-administration extend prior findings in nonhumans and alcoholics to moderate drinkers. Such consistencies support a position that a common set of variables control alcohol self-administration across these populations.