When a cell membrane is attached to an inert surface, ionic current may flow from the bath along the narrow cleft between membrane and surface into the cell kept at constant potential. This current modifies the voltage across the membrane due to the voltage-drop in the cleft. As a result the conductance of voltage-gated ion channels is affected. By positive feedback, smooth gating is transformed into switching with bistability, hysteresis and memory as shown by cable theory. Self-gating in cell adhesion is triggered by minute modulations of the attachment or of the intracellular potential.
Fig.3: Profile of the membrane conductance gJM in a circular junction with a radius aJ=10 µm for three distances between membrane and surface. At dJ=5.5 nm the membrane is in a state of high conductance. At dJ=6.5 nm there are two stable stationary states. At dJ=7.5 nm the membrane is in a state of low conductance. The parameters are: Maximum conductance g0=100mS/cm2, gating charge qG=2e0, reversal voltage V0=+50mV, gating voltage VG=0mV, intracellular voltage VM=-50mV, specific resistance Ro0=100MWcm.
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