Effects of Aminooxyacetic Acid and Baclofen on the Catalepsy and on the Increase of Mesolimbic and Striatal Dopamine Turnover Induced by Haloperidol in Rats

Effects of aminooxyacetic acid (AOAA) and baclofen on the catalepsy and on the increase of mesolimbic and striatal dopamine turnover induced by haloperidol were studied in rats. AOAA (25 mg/kg intraperitoneally) which increases the cerebral concentration of δ–aminobutyric acid (GABA) and baclofen (10 mg/kg intraperitoneally), a structural analogue of GABA, did not induce catalepsy by themselves but potentiated the catalepsy caused by haloperidol (0.1 mg/kg subcutaneously). AOAA and baclofen did not alter the haloperidol–induced striatal homovanillic acid increase. AOAA and baclofen decelerated the dopamine disappearance caused by α–methyl–p–tyrosine (αMT) both in mesolimbic nuclei and striatum. Haloperidol accelerated the αMT–induced dopamine disappearance in these structures. AOAA and baclofen prevented this stimulatory effect of haloperidol on the dopamine turnover. These results support the earlier suggestions that GABAergic pathways have an inhibitory effect on the mesolimbic and striatal dopaminergic pathways.