Abstract
The depolarizing drive that maintains bursting inHelix neurons is carried by a long-lasting calcium-activated inward current. This current was studied using cell-attached and inside-out patches from the right parietal fast burster neuron ofHelix pomatia.
One population of unitary currents was inward at −50 mV and showed an increased probability of opening when Ca2+ was injected or when excised patches were bathed in solutions with 10−7 to 10−5 M free Ca2+ levels. Cell-attached patches (patch electrodes filled with 10−7 M Ca2+ Ringer) had single channel conductances near 30 pS with reversal potentials near −20 mV; excised patches had similar conductances in symmetrical Na+ solutions and reversal potentials within a few millivolts of zero. Calculations, assuming a simple spherical cell, yield a channel density of only about 1/6 μm2. The increased channel opening probability characteristically persisted well beyond the duration of transient whole-cell inward current. We conclude from this that the later phase of Ca-activated inward currents is normally masked by outward currents.
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Partridge, L.D., Swandulla, D. Single Ca-activated cation channels in bursting neurons ofHelix . Pflugers Arch. 410, 627–631 (1987). https://doi.org/10.1007/BF00581323
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DOI: https://doi.org/10.1007/BF00581323