Effects of intranigral injection of taurine and GABA on striatal dopamine release monitored voltammetrically in the unanaesthetized rat.

Linear sweep voltammetry with carbon-paste electrodes was used to detect changes in the extracellular concentration of homovanillic acid (HVA) in the striatum of unanaesthetized rats; under the present experimental conditions, changes in the HVA signal were used as an index of striatal dopamine release. The effects of unilateral intranigral infusion of saline, sucrose, taurine, GABA and the putative taurine-receptor antagonist, 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide (TAG), on the HVA signal were monitored in the striatum on the two sides of the brain. Both taurine and GABA caused an increase in the extracellular concentration of HVA which was significantly greater in the striatum on the side of the injection compared with the contralateral side. The effect of TAG varied between animals. The results are discussed in terms of the role of taurine as a possible neuromodulator in the substantia nigra and in the light of the suggestion that different pathways are involved in taurine- and GABA-induced contraversive circling.