USE OF A VIBRATING ELECTRODE TO MEASURE CHANGES IN CALCIUM FLUXES ACROSS THE CELL-MEMBRANES OF OXIDATIVELY CHALLENGED APLYSIA NERVE-CELLS

A self-referencing and non-invasive Ca2+-sensitive vibrating electrode was used to assess the effects of hydrogen peroxide-induced oxidative challenges on the efflux and influx of calcium across the plasma memb rane of single nerve cells cultured from abdominal ganglion of Aplysia californica. A reduced net efflux of Ca2+ from the cell soma occurred immediately after the addition of hydrogen peroxide (0.0025 mM, 0.005 mM or 0.01 mM) to the culture medium, indicating damage to the cell m embrane or Ca2+ transport mechanism. There then followed a marked effl ux, the extent and duration of which was related to the concentration of hydrogen peroxide used and which may reflect compensatory activity by the Ca2+ regulatory mechanisms in the plasmalemma. No morphological changes were observed in cells challenged with 0.0025 mM hydrogen per oxide and the enhanced rate of Ca2+ efflux rapidly decreased to pre-ex posure values. Sustained and enhanced Ca2+ effluxes from those cells e xposed to 0.005 mM or 0.01 mM hydrogen peroxide were also consistent w ith regulatory pumping of Ca2+ out of the cell although contraction an d blebbing of neurites and swelling of the soma may indicate that a pr oportion of the efflux arose from release of Ca2+ from disrupted intra cellular stores. The vibrating electrode is a useful additional techni que for the study of the pathogenesis of neurological conditions, as i onic fluxes across single nerve cells exposed to physiologically-relev ant concentrations of free radicals can be monitored non-invasively fo r prolonged periods.