Aspartate-induced changes in extracellular free calcium in 'in vitro' hippocampal slices of rats.
Extracellular free calcium ([Ca2+]0) and neuronal activity were measured with double-barreled Ca2+-selective/reference microelectrodes in the CA1 field of rat hippocampal slices during stimulation of Schaffer collaterals and during iontophoretic application of the excitatory amino acid aspartate (Asp). Baseline [Ca2+]0 was 1.5 mM. Repetitive stimulation and aspartate application caused decreases in [Ca2+]0 (delta Ca), which were largest in the pyramidal cell layer. During iontophoretic application of GABA, aspartate often failed to induce significant alterations in [Ca2+]0. Mg2+ (9 mM) and Ni2+ (3mM) when added to the perfusion medium reduced aspartate-dependent delta Ca by 15 and 70% respectively. In tetrodotoxin (10(-6) M) containing Ringer the aspartate-induced delta Ca were about 10% smaller. These findings suggest that the decreases in [Ca2+]0 are mainly due to a postsynaptic Ca2+ entry through selective Ca2+ conductances.
D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D046508:Culture Techniques; D005110:Extracellular Space / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009532:Nickel / Q000494:pharmacology; D051381:Rats; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D007473:Ion Channels; D001224:Aspartic Acid; D008345:Manganese; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D009532:Nickel; D008274:Magnesium; D002118:Calcium