ATTENUATION OF HIGH VOLTAGE-ACTIVATED CA2-DOWN IN RAT HIPPOCAMPAL CA1PYRAMIDAL CELLS BY NAF( CURRENT RUN)

Calcium currents in CA1 neurons from rat hippocampus were studied with the whole-cell, patch-clamp technique. Under control conditions high- voltage-activated (HVA) calcium currents activated from membrane poten tials of -80 mV and -40 mV underwent ''run-down''. The rate of run-dow n of the current activated from -40 mV was significantly attenuated by inclusion of the G-protein activator NaF (1 mM) in the pipette and al so irreversibly attenuated by brief batch application of NaF (10 mM). This effect was significantly reduced by inclusion of high (10 mM) eth yleneglycoltetraacetate (EGTA) concentrations in the pipette, suggesti ng an involvement of calcium-dependent processes. It is suggested that activation of guanine nucleotide-binding proteins by NaF leads to a l ong-lasting attenuation of HVA calcium current run-down in hippocampal CA1 cells.