Striatal extracellular levels of dopamine and its metabolites during kainate-induced limbic seizures in freely-moving rats measured by brain microdialysis

To investigate the role of brain dopaminergic systems in epilepsy, striatal extracellular levels of dopamins (DA) and its metabolites (3,4-dihydroxyphenylacetic acid : DOPAC and homovanillic acid : HVA) were measured during kainate-induced limbic seizures in freely-moving rats, using brain microdialysis. DA and its metabolites were measured by high performance liquid chromatography. Systemic injection of kainate (10mg/㎏, i. p.), which caused stable limbic seizures, significantly decreased the levels of DA and its metabolites. Intrahippocampal injection of kainae (2.5nmol), which also caused limbic seizures, significantly decreased only the DA levels, while DOPAC and HVA levels were unchanged. Similar to the results of the systemic injectjon, intrastriatal perfusion of kainate (10(-2) or 10(-6) M) significantly decreased the levels of DA, DOPAC and HVA in a dose-dependent manner. These findings indicate that, during kainate-induced limbic seizures, DA release was significantly reduced in the striatum. In conclusion, the hypofunction of striatal dopaminergic systems is related to the initiation and progress in epileptic seizures.

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