The cell line M213-2O CL-4 was derived from cell line M213-2O and further modified to express human glutamate decarboxylase (hGAD-67), the enzyme that synthesizes GABA. Brain transplants of this cell line in animal models of epilepsy have been shown to modulate seizures. However, the mechanisms that underlie such actions are unknown. The purpose of the present study was to characterize this cell line and its responsiveness to several depolarizing conditions, in order to better understand how these cells exert their effects. Intracellular GABA levels were 34-fold higher and GAD activity was 16-fold higher in clone M213-2O CL-4 than in M213-2O. Both cell lines could take up [³H]GABA in vitro, and this uptake was prevented by nipecotic acid. By combining GABA release measurements and calcium imaging in vitro, we found that high extracellular K(+), zero Mg(2+), or glutamate activated M213-2O CL-4 cells and resulted in GABA release. The response to glutamate appeared to be mediated by AMPA/NMDA-like receptors. High KCl-induced GABA release was prevented when a Ca(2+)-free Krebs solution was used, suggesting an exocytotic-like mechanism. These results indicate that the cell line M213-2O CL-4 synthesizes, releases, and takes up GABA in vitro, and can be activated by depolarizing stimuli.

The herbicide atrazine (ATR) has a potential toxic effect on the neuronal circuits of the brain, specifically on two major dopaminergic pathways: the nigrostriatal and mesolimbic circuits. In this work, we repeatedly exposed adult male Sprague-Dawley rats to 6 injections of 100 mg ATR/kg of body weight (for two weeks) and one saline injection two days after ATR administration. Locomotor activity was assessed for 15 minutes and/or 2 hours after ATR or saline injection and 2 months after the final ATR administration. The specific binding of [3H]-SCH23390 to D1-DA receptors and that of [3H]-Spiperone to D2-DA receptors in the dorsal and ventral striatum were assessed 2 days and 2 months after ATR treatment. ATR administration resulted in immediate, short- and long-term hypoactivity and reduced specific binding of [3H]-SCH23390 in the dorsal striatum of rats evaluated 2 months after the last ATR injection. The specific binding of [3H]-SCH23390 in the ventral striatum and the specific binding of [3H]-Spiperone in the dorsal and ventral striatum remained unchanged at 2 days or 2 months after ATR treatment. These results, together with previous findings of our group, indicate that the nigrostriatal system is a preferential target for ATR exposure.