STIMULATION OF DOPAMINE TRANSMISSION IN THE DORSAL CAUDATE-NUCLEUS BYPARGYLINE AS DEMONSTRATED BY DOPAMINE AND ACETYLCHOLINE MICRODIALYSISAND FOS IMMUNOHISTOCHEMISTRY

The effect of pargyline on dopamine neurotransmission was investigated by transtriatal microdialysis combined with Fos immunohistochemistry. Pargyline, 75 mg/kg i.p., increased dopamine and acetylcholine output while drastically decreased dopamine deaminated metabolites. Administ ration of pargyline resulted in the appearance of Fos-positive nuclei distributed along a gradient around the dialysis probe. Pretreatment w ith the D1 antagonist SCH 23390 potentiated the effect of pargyline on dopamine output while preventing that on acetylcholine output and on Fos formation. Similarly, lack of calcium in the perfusion medium abol ished the effect of pargyline on dopamine and acetylcholine output and on Fos formation. In rats not implanted with dialysis probes pargylin e administration resulted in only rare Fos-positive nuclei in the dors al caudate. The present study indicates that pargyline stimulates dopa mine transmission in the dorsal caudate in the area around the dialysi s probe but not distant from the fibre or in unimplanted rats. This ef fect appears to reflect an interaction between the drug-induced change s and those locally elicited by the probe.