Kainic Acid-Stimulated Release of Taurine and Gaba from the Rat Globus Pallidus and Substantia Nigra in Vivo

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The basal ganglia are a group of subcortical nuclei intimately involved in the control of movement. The major input to the basal ganglia arises in the cortex and is carried by the corticostriatal projection. The cortical information is processed in the striatum and then transmitted to the output nuclei of the basal ganglia, the entopeduncular nucleus and the substantia nigra pars reticulata (SNr), by either the direct or the indirect pathways. The direct pathway consists of a direct projection from the striatum to the entopeduncular nucleus or SNr, the indirect pathways consist of a striatal projection to the globus pallidus and thence to the output nuclei or to the output nuclei via the subthalamic nucleus. Striatal projection neurons, neurons of the globus pallidus, SNr and entopeduncular nucleus are GABAergic whereas those of the subthalamic nucleus use glutamate. Activation of the direct pathway leads, by virtue of its GABAergic nature, to inhibition of neurons in the entopeduncular nucleus and SNr whereas activation of the indirect pathways produces the opposite effect i.e. disinhibition (1-3) of neurons in the entopeduncular nucleus and SNr. Neurones identified as medium-size densely spiny striatonigral neurones have also been shown to accumulate exogenous taurine and release it at their terminals in the SN (4).