THE FAILURE OF COCAINE TO SERVE AS AN ORALLY SELF-ADMINISTERED REINFORCER IN LEWIS RATS

The aim of this study was to develop a procedure to establish orally d elivered cocaine as a reinforcer for rats. Several procedures that hav e proven reliable in other studies were instituted. (1) Food-induced d rinking: food was presented to engender high rates of drinking, then c ocaine solutions replaced water, and finally the food was removed. Pea k drug intakes ranged from 9.4 to 13.8 mg/kg. (2) Ethanol-fade: ethano l was established as a reinforcer, cocaine was gradually added to the ethanol, and the ethanol was gradually removed. Peak cocaine intakes r anged from 3.6 to 5.2 mg/kg. (3) Modified food-induced drinking: food was presented, but was followed by a timeout period, allowing digestio n to progress prior to cocaine drinking. Peak drug intakes ranged from 12.9 to 18.6 mg/kg. However, cocaine was not established as a reinfor cer with any of these methods. High cocaine doses may be necessary, bu t are not sufficient, to establish oral cocaine self-administration In rats.