The present study demonstrated that it is possible to measure the endogenous extracellular dopamine (DA) and its metabolite dihydroxyphenylacetic acid (DOPAC), endogenous extracellular 5-hydroxytryptamine (5HT), its metabolites 5-hydroxyindoleacetic acid (5HIAA), 5-hydroxytryptophol (5HTOL) and its precursor 5-hydroxytryptophan (5HTP) simultaneously from the striatum of freely moving rats using intracerebral dialysis combined with high performance liquid chromatography (HPLC) with electrochemical detector (ECD).

Basal extracellular levels of DA, DOPAC, 5HTP, 5HT, 5HIAA and 5HTOL in the striatum were estimated to be 18.89 ±. 2.23 (pg/25 μl/60 min), 7.25 ± 0.32 (ng/25 μl/60 min), 13.35 ± 3.01 (pg/25 μl/60 min), 5.32 ± 0.92 (pg/25 μl/60 min), 2.41 ± 0.08 (ng/25 μl/60 min) and 7.69 ± 0.45 (pg/25 μl/60 min), respectively. Pargyline (75 mg/kg i.p.) and tryptophan (100 mg/kg i.p.) increased the 5HT level in the striatum perfusates by 3-fold, whereas DOPAC and 5HIAA levels decreased by approximately 20% and 8%, respectively. In addition, DA and 5HTOL levels were not changed.

This method is suitable for monitoring dopaminergic and serotonergic activities dynamically.