TAURINE INFUSED INTRASTRIATALLY ELEVATES, BUT INTRANIGRALLY DECREASESSTRIATAL EXTRACELLULAR DOPAMINE CONCENTRATION IN ANESTHETIZED RATS

In the present study we infused taurine (50, 150 or 450 mM, 2 mu l/min for 4 h) into the dorsal striatum or into the substantia nigra via mi crodialysis probe and estimated the extracellular concentrations of do pamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in the dorsal striatum of anaesthetised rats . Intrastriatal infusion of taurine elevated striatal dopamine at all concentrations studied. At the 450 mM concentration taurine elevated t he extracellular dopamine 10-fold, but only in the first 30 min sample after starting the taurine infusion. At 50 and 150 mM taurine elevate d dopamine throughout the 4 h infusion maximally up to 3-4-fold the co ntrol level. Extracellular DOPAC was increased by 150 and 450 mM tauri ne (up to about 150-160% of the control level), whereas at all three c oncentrations taurine decreased HVA to about 85% of the control; howev er, the decrease caused by 450 mM taurine was short-lasting. At all th ree concentrations taurine infused into the substantia nigra decreased the extracellular dopamine in the ipsilateral striatum to about 40-50 % of the control, and increased extracellular DOPAC and HVA maximally to about 150% and 170% of the control, respectively. These results sho w that the effects of taurine on the concentrations of extracellular d opamine and its metabolites depend on its administration site on nigro striatal dopaminergic neurons. It elevates the extracellular dopamine when given into the striatum, but when given into the cell body region of the nigrostriatal dopaminergic pathway it decreases the extracellu lar dopamine in the ipsilateral striatum.