Responding under a fixed interval schedule of intravenous ethanol presentation in the rat

Specific behavioural procedures have been developed which lead animals to give themselves electric shock. The present study investigated the possibility that the same set of procedures would lead to intravenous (i.v.) ethanol self-administration. Three rats were trained to press a bar under a concurrent schedule which delivered food pellets on a variable interval (VI) 60 sec or 120 sec schedule and ethanol infusions on a fixed interval (FI) 600 sec schedule. A fourth animal was trained under the same concurrent schedule with vehicle rather than ethanol infusions. When the food schedule was subsequently omitted (extinction) and only ethanol was presented for responding, bar pressing rapidly extinguished. In one animal tested with a very high dose of ethanol, drug-elicited bar pressing indicative of an aversive reaction to the drug was observed. Although similar procedures are sufficient to engender response-produced shock presentation they were not successful in fostering i.v. ethanol self-administration and by implication, in establishing ethanol as a positive reinforcer.