Segal_1992_Brain.Res_587_83

The effects of acetylcholine (ACh) on changes in [Ca]i produced by the glutamate agonist N-methyl-D-aspartate (NMDA) were measured in cultured rat hippocampal neurons loaded with the fluorescent calcium indicator Fluo-3 in a confocal laser scanning microscope. NMDA produced a dose-dependent reversible rise in [Ca]i. ACh had a smaller and less consistent effect on [Ca]i but could cause a marked enhancement of the reactivity of neurons to NMDA. This effect was reversed by the presence of the muscarinic antagonist atropine. AMPA, another glutamate agonist which causes a rise in [Ca]i by activating voltage gated calcium influx was less affected by ACh. Caffeine, which releases calcium from intracellular stores also enhanced reactivity of these neurons to NMDA. It is suggested that ACh can enhance reactivity to NMDA by releasing calcium from internal stores.