Effect of chronic treatment with SCH 23390 and haloperidol on spontaneous activity of dopamine neurones in substantia nigra pars compacta (SNC) and ventral tegmental area (VTA) in rats.

The effect of chronic treatment (21 days s.c.) with SCH 23390 and haloperidol on spontaneously active DA neurones in substantia nigra pars compacta (SNC) and ventral tegmental area (VTA) was studied in rats by means of single unit recording techniques. The specific DA D-1 receptor antagonist SCH 23390 was injected twice daily in one of the following doses: 0.06, 0.23, 0.46 or 0.90 mumol/kg. SCH 23390 decreased the number of spontaneously active neurones in SNC and VTA to the same extent. The DA D-2 receptor antagonist haloperidol was injected once daily in one of the following doses: 0.05, 0.21 or 1.7 mumol/kg and induced a decrease in the number of spontaneously active DA neurones in SNC and VTA. These results suggest that SCH 23390 has a profile similar to that of haloperidol and that SCH 23390 has clinical antipsychotic activity but also induces extrapyramidal side-effects.