Loxapine and clozapine decrease serotonin (S2) but do not elevate dopamine (D2) receptor numbers in the rat brain.

Chronic administration of loxapine or clozapine in rats for 4 weeks or 10 weeks did not produce enhancement of striatal dopamine receptor density. However, there was a marked reduction (50-60%) of cortical serotonin receptor density associated with clozapine or loxapine administration. Acute doses of clozapine or loxapine produced the same potent effect. The possibility that these two antipsychotic drugs act via the serotonin system in the brain is proposed.