Effects of taurine and glycine on epileptiform activity induced by removal of Mg2+ in combined rat entorhinal cortex-hippocampal slices

Purpose: The imbalance between neuronal inhibition and excitation contributes to epileptogenesis. Inhibition in the central nervous system (CNS) is mediated by gamma-aminobutyric acid (GABA) and glycine. Recent studies indicate the expression of glycine receptor (GlyR) in hippocampus and neocortex. However, the function of GlyR in these regions is not clarified completely. The aim of this study was to investigate whether the GlyR agonists glycine and taurine promote an anticonvulsive effect. Methods: We induced epileptiform discharges by reducing extracellular Mg2+ concentration in combined rat entorhinal cortex-hippocampal slices (400 mum). Epileptiform discharges were detected by using extracellular recording techniques. Results: Seizure-like events were suppressed by taurine, exhibiting, a half-maximal inhibitory effect (IC50) Of 0.9 mM. Suppression of late recurrent discharges in the medial entorhinal cortex and recurrent short discharges in the hippocampus was obtained at an IC50 value of 1.6 and 2.1 mM, respectively. Strychnine at concentrations <1 muM abolished these effects. Likewise glycine, after an initial proconvulsant effect, suppressed epileptiform discharges. Conclusions: These findings show that GlyR agonists, in particular taurine, could serve as potential anticonvulsants and suggest an important role of GlyR in cortical function and dysfunction.