Fig. 7. The mGluR5 antagonist MPEP inhibits low [Mg2+]o-induced PI incorporation in the CA1 regions of rat hippocampal slices.
Hippocampal slices were exposed to normal [Mg2+]o or low [Mg2+]o DMEM solution (See METHODS) for 24 h in the absence or presence of mGluR antagonists such as MPEP (50 µM) and LY367385 (100 µM). The viability of neuronal cells was assessed by PI incorporation after 30 min exposure to the red fluorescent dye, PI. PI incorporation was shown as a percentage of 70% ethanol-induced maximal PI. (A) Bar graph shows PI incorporation in non (control: normal [Mg2+]o, n = 12; low [Mg2+]o, n = 14)-, MPEP (normal [Mg2+]o, n = 7; low [Mg2+]o, n = 6)- and LY367385 (normal [Mg2+]o, n = 6; low [Mg2+]o, n = 6)-treated groups in the CA1 and CA3 regions. Exposure to normal [Mg2+]o DMEM solution induced a basal PI incorporation. Exposure to low [Mg2+]o DMEM solution significantly increased PI incorporation in the CA1 and CA3 regions. MPEP significantly decreased the low [Mg2+]o-induced PI incorporation in the CA1 region. However, MPEP or LY367385 did not affect the low [Mg2+]o-induced PI incorporation in the CA3 region. (B) Representative phasecontrast photomicrographs showing rat hippocampal slices 24 h after exposure to normal [Mg2+]o or low [Mg2+]o DMEM solution in the absence or presence of mGluR antagonists. Data are expressed as means ± SEM. mGluR, metabotropic glutamate receptor; MPEP, 6-Methyl-2-(phenylethynyl) pyridine; [Mg2+]o, extracellular Mg2+ concentration; PI, propidium iodide; DMEM, Dulbecco’s modified eagle media. **p < 0.01 relative to respective control, ##p < 0.01 relative to normal [Mg2+]o. Scale bars: 100 μm.
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