Acute and chronic effects of neuroleptics and acute effects of apomorphine and amphetamine on dopamine turnover in corpus striatum and substantia nigra of the rat brain.

The effects of chronic neuroleptic treatment on the concentrations of homovanillic acid (HVA) and 3,4-dihydroxy-phenylacetic acid (DOPAC) in the rat substantia nigra (SN) and corpus striatum (CS) were determined. Acute haloperidol and alpha-flupenthixol increased HVA and DOPAC in the CS but after chronic treatment no significant change was found compared to controls. In the SN, on the contrary, acute haloperidol reduced and subsequently increased HVA and DOPAC and alpha-flupenthixol had no significant effect, whereas chronic treatment with either neuroleptic increased the levels of the metabolites. Acute apomorphine reduced HVA and DOPAC in CS, but increased first and subsequently decreased the levels of the metabolites in the SN. Acute amphetamine reduced both metabolites in SN and DOPAC in CS, whereas striatal HVA was unaffected. The different or even reciprocal effects on DA release may suggest an independent local action of these drugs in CS and SN.