GLUTAMATE RECEPTOR-MEDIATED CALCIUM SURGES IN NEURONS DERIVED FROM P19 CELLS

Retinoic acid-treated murine Pig embryonal carcinoma cells differentiate into cells with neuronal morphology that display typical neuronal markers. In this study, the presence of glutamate receptors linked to Ca2+-signaling mechanisms on these neurons was demonstrated by testing the effects of glutamate agonists and antagonists on the intracellular calcium ion concentration ([Ca2+](i)). Glutamate (1 mM) induced either sustained or transient increases in [Ca2+](i). The sustained glutamate-induced increase in [Ca2+](i) was mimicked by NMDA (40 mu M). The NMDA-triggered [Ca2+](i) response was abolished by incubating the cells in Ca2+-free medium or by pretreating them with Mg2+ (2 mM) or MK-801 (0.1 mu M). These responses were unaffected by the non-NMDA antagonist CNQX(10 mu M), but they required glycine (3-30 mu M). Kainate (40 mu M) and AMPA (40 mu M) did not affect [Ca2+](i). Without external Ca2+, glutamate triggered transient, sometimes oscillating, increases in [Ca2+](i). These responses were mimicked by the metabotropic agonist trans-(1S, 3R)-1-amino-1,3-cyclopentanedicarboxylic acid (300 mu M). These results suggest that neurons derived from P19 embryonal carcinoma cells have NMDA and metabotropic, but not AMPA/kainate receptors, which are linked to Ca2+-signaling mechanisms. These cells could provide a consistent and reproducible model with which to study neuronal differentiation, neurotoxicity, and glutamate receptor-signaling mechanisms.