Establishment and maintenance of oral ethanol self-administration in the baboon

A simple and reliable method was developed to study the self-administration of orally available ethanol by baboons. Two baboons were individually housed in a minimally controlled laboratory environment with visual and auditory access to other baboons and to laboratory technicians. The cages were equipped with standard drinking bottles and spouts. Each baboon was fed his entire daily ration of dry food at the same time each morning, at which time a fresh solution was added to the liquid reservoir. Three hours later, the amount of liquid consumed was measured. This procedure generated high rates of water drinking during the 3-h sessions ("food-induced drinking"). Next, the water available during the sessions was replaced by gradually increasing concentrations of aqueous ethanol (0.5-8%, w/v). When 8% ethanol was reached, the concentration was held constant across daily sessions as session feedings were gradually reduced and shifted to 30 min postsession. Eventually, daily test sessions consisted of simply 3 h access to ethanol, and water was continuously available during the 21-h intersession period. Over a range of ethanol concentrations of 8-32%, ethanol intake (g/kg) and blood ethanol levels remained fairly constant, while volumes (ml) of solution consumed were inversely related to the concentration. Finally, an additional liquid spout was added to each cage and the baboons were provided concurrent access to both ethanol (8%) and water during the sessions. The results indicated clearly that ethanol had come to serve as a positive reinforcer for both of these baboons. This simple preparation should be particularly useful in laboratories that are not equipped with the elaborate technology required in earlier described preparations, and might lend itself to the study of orally effective drugs other than ethanol.