Generation of Ca2+ Signal in NMDA Receptors of Rat and Rabbit Hippocampus in Vivo

The role of Ca2+ in neurotransmission and intraneuronal signal transduction under normal conditions, and its involvement in acute and chronic neurodegenerations has been presented in detail in many recent reviews (1–3). Regulatory and neurotoxic increases in intracellular Ca2+ concentration ([Ca2+]i) may result from influx of extracellular Ca2+ to neurones, which in vivo leads to corresponding decrease in extracellular Ca2+ concentration ([Ca2+]e) and/or from its mobilisation from intracellular stores. Failure of Ca2+ extrusion from the cell via ATP-driven Ca2+ pump and the Na+/Ca2+ antiporter may also participate in this process (4, 5).