Defense Date


Document Type


Degree Name

Doctor of Philosophy



First Advisor

Joseph H. Porter, Ph.D


Amisulpride, a benzamide derivative, is an atypical antipsychotic drug used to treat both schizophrenia and depression. Amisulpride is a selective antagonist at dopamine D2 and D3 receptors and at serotonin 5-HT2B and 5-HT7 receptors and displays an atypical clinical profile with reduced extrapyramidal motor effects. The drug has a chiral center and is a mixture of two optical isomers: (S)-amisulpride and (R)-amisulpride. The present study used a two-lever drug discrimination assay to allow a direct comparison between amisulpride and its two isomers. Additionally, substitution testing was conducted with the typical antipsychotics, atypical antipsychotics, antidepressants, the anxiolytic chlordiazepoxide, several benzamide derivatives, and selective ligands with receptor mechanisms relevant to amisulpride.

C57BL/6 mice were trained to discriminate 10 mg/kg rac-amisulpride from vehicle in a two-lever drug discrimination task for food reinforcement in an average of 35.7 sessions (range 6-89). The amisulpride dose-response curve (0.078 – 10.0 mg/kg) yielded an ED50 = 0.64 mg/kg, 95% CI [.47, 0.84 mg/kg]. The isomers fully substituted for amisulpride with a significant left-ward shift in the dose-response curve for (S)-amisulpride as compared to rac-amisulpride and (R)-amisulpride. The benzamide derivatives sulpiride and the (S)-sulpiride isomer fully substituted for amisulpride; tiapride produced partial substitution (76.4% DLR); none of the other tested drugs substituted for rac-amisulpride’s discriminative stimulus. These results showed that the rac-amisulpride stimulus was readily acquired in C57BL/6 mice, and that it has a unique and robust discriminative stimulus that is dose-dependent, time-dependent and stereoselective and is not shared with other antipsychotic or antidepressant drugs.


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