Self-stimulation and alcohol administered orally or intraperitoneally

The relationships in rats between the reinforcing value of electrical self-stimulation of the brain and varying concentrations of ethanol in the drinking solution (from 5 to 40% v/v alcohol) or in i.p. injections (0.3, 0.6, 1.2, and 1.8 g/kg of alcohol) were studied. The reinforcing value of brain stimulation was quantified using the total time spent in self-stimulation and the number of bar pressings. Results showed that the relationships depended on the ethanol concentration, the degree of reinforcement of the brain stimulation, and the route of administration of the ethanol solution. Particularly, a small dosage injected intraperitoneally or ingested orally accentuated the reward produced by an electrical brain stimulation when the self-stimulation performance was still high. On the contrary, a large dosage of alcohol always dramatically depressed the self-stimulation performance.