Spontaneous activity of A9 and A10 dopamine neurons after acute and chronic administration of the selective dopamine D-1 receptor antagonist SCH 23390.

The effects of acute and chronic treatment with the selective dopamine (DA) D-1 antagonist SCH 23390 on the population response of midbrain DA cells were determined. One hour pretreatment with SCH 23390 (0.0125, 0.025, 0.05 mg/kg s.c.) caused a dose-related increase in the number of spontaneously firing DA neurons in both the A9 and A10 cell regions. Chronic (28 day) administration of SCH 23390 (0.05 mg/kg s.c.) caused depolarization inactivation of only A10 DA cells. These data suggest that SCH 23390 may have antipsychotic properties with a reduced likelihood of producing extrapyramidal side effects.