Group II mGlu receptor agonists fail to protect against various neurotoxicinsults induced in murine cortical, striatal and cerebellar granular pure neuronal cultures

Since group II metabotropic glutamate (mGlu) receptors are a potential targ et for the amelioration of neuronal injury, we evaluated the ability of gro up II mGlu receptor agonists to attenuate toxicity induced by various insul ts in cortical, striatal and cerebellar granular (CGCs) pure neuronal cultu res. The three cultures, when maintained under serum-free, anti-oxidant ric h conditions for up to 13 days in vitro (div) were shown by immunocytochemi stry to contain a maximum of 2-7% glia. At 6, 9 and 13 div a graded pattern of injury to cortical and striatal cultures was achieved with either hydro gen peroxide (60-110 muM), staurosporine (1 muM), N-methyl-D-aspartate (NMD A, 70 muM), alpha -amino-3-hydroxy-methylisoxazole-4-propionate (AMPA, 100 muM) or kainate (100 muM) over either 4, 24 or 48 h. CGCs were similarly ex posed to low K+ (5.4 mM KCI). Cell viability was examined via phase-contras t microscopy and assessed by a 3-(4,5-dimethylthiazole-2-yl)-2.5-diphenylte trazolium bromide assay. Treatment with group II mGlu receptor agonists (1- 300 muM), 2R,4R-3-aminopyrrolidine-2,4-dicarboxylate ((2R,4R)-APDC), (2S,1' S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), (2S,2'R,3'R)-2-(2',3'-dicar boxycyclopropyl)glycine (DCG-IV) and N-acetylaspartylglutamate (NAAG) faile d to attenuate the toxicity. Pretreatment of cultures with the agonists and treatment following acute insult also failed to attenuate toxicity. Furthe r investigations demonstrated the presence of second messenger activation w hereby (2R,4R)-APDC reduced forskolin-stimulated production of cAMP in each culture. Thus, despite receptor coupling to intracellular signaling cascad es, and regardless of culture development, agonist concentration, extent an d mode of injury, group II mGlu receptor agonists were unable to protect ag ainst injury induced in cortical, striatal and cerebellar granular pure neu ronal cultures. This result is in contrast to mixed cultures of neurones an d glia and implies an important role for glia in the neuroprotective effect s of group II mGlu receptor agonists. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.