Changes in dopamine D1, D2 and D3 receptor mRNA levels in rat brain following antipsychotic treatment

The effects of administration of antipsychotic drugs (1–32 days, twice per day) on the rat brain mRNA levels of dopamine D1, D2 and D3 receptors has been assessed by a novel procedure utilising solution hybridisation with oligonucleotides. Saline and sulpiride (10 mg/kg/injection) had no effect on D1, D2 and D3 receptor mRNA levels. Haloperidol (1.5 mg/kg/injection) elicited increases in D1, D2 and D3 receptor mRNA levels of 100%, 100% and 300%, respectively, after 32 days and loxapine (2 mg/kg/injection) elicited increases of 450%, 150% and 550%, respectively. These results indicate that the up-regulation of dopamine receptors may be associated with the occurrence of tardive dyskinesia but not the clinical mode of action of antipsychotics