Facilitating role of m-chlorophenylbiguanide in a cocaine discrimination

To examine the interaction between serotonergic systems and the discriminative stimulus effects of cocaine, the effects of the selective 5-HT3 agonist mCPBG were examined in 46 Sprague-Dawley rats trained to discriminate 10 mg/kg cocaine from saline. mCPBG substitution tests showed partial substitution for the cocaine stimulus. In interaction tests, the combination of mCPBG and low doses of cocaine resulted in increased cocaine lever selection. mCPBG treatment reduced response rates, but not below a 50% criterion. These results point toward a limited modulatory role of serotonergic systems in the cocaine discriminative stimulus.