Cocaine is a highly addictive psychostimulant that is widely used around the world. It is far more cost effective to curb this problem through treatment than by any other method as medicinal drug treatment is 15 times more effective than law enforcement at reducing the societal costs of cocaine use as determine by RAND corp. In a previous paper from our lab, it was found that via virally mediated introduction of additional 5-HT1B receptors into the nucleus accumbens there was a leftward shift in the cocaine intake dose-response curve in animals that were self-administering cocaine by pressing a lever. These findings suggest that 5-HT1B receptor action enhances the reinforcing effects of cocaine. However, when animals were given a 21-day period of prolonged abstinence and then tested for cocaine intake, it was determined that 5-HT1B receptor action had the opposite effect of decreasing cocaine intake presumably due to a decrease in the reinforcing effects of cocaine: [16]. The experiment in the current paper was devised to further test this finding via pharmacological means using the 5-HT1B agonist CP 94253 to increase stimulation of 5-HT1B receptors. Animals were trained to self-administer by pressing a lever on fixed ratio schedules of cocaine reinforcement given at 0.75 mg/kg and 0.075 mg/kg doses of cocaine. These doses allowed us to examine changes in self-administration on both the ascending and descending limbs of the inverted u-shaped cocaine dose-effect curve. Our results indicated that in animals given CP 94253 exhibited a decrease in responding on both the ascending and descending limbs of the dose response curve demonstrating a downward shift after prolonged abstinence. These exciting results suggest that the agonist decreases cocaine intake, and therefore, the agonist may be a useful treatment for cocaine dependence.