WHOLE-CELL MEMBRANE CURRENT AND MEMBRANE RESISTANCE DURING HYPOXIC SPREADING DEPRESSION

IN rat hippocampal tissue slices we recorded extracellular potential (V(o)) and whole-cell patch clamp current of CA1 pyramid cells. During hypoxic spreading depression (SD)-like depolarization, the holding current (I(h)) increased sharply. Membrane 'slope' resistance (R(m)) decreased to 10-67% (mean 39%) of the resting value. The SD-related membrane current (I(SD)) reversed near zero mV. With voltage dependent K+ and Na+ currents blocked by Cs+ and QX-314, shifts of I(h) and decrease of R(m) during SD were not suppressed. We conclude that hypoxic SD of CA1 pyramidal cells is associated with a large non-selective inward current through yet to be identified membrane mechanisms, which cannot fully explain the SD-related V(o) shift.