Chemically modified Na + channels exhibit a characteristic bursting state much shorter than in DPI-modified Na + channels, a difference not consistent with the hypothesis of common kinetic properties in noninactivating Na + channels.Īldrich, R.W., Corey, D.P., Stevens, C.F. The underlying deactivation process is strongly voltage sensitive but, in contrast to slow Na + inactivation, responds to a voltage shift in the positive direction with a retardation in kinetics. Despite removal of inactivation, open probability progressively declined during membrane depolarization. Of the two substates observed, one of them is remarkable in that it is mostly attained from full-state openings and is very short living in nature the voltage-independent lifetime was close to 2 msec. Chemically modified Na + channels retain an apparently normal unitary conductance (12.8☐.5 pS). Also, burst duration depended apparently exponentially on voltage and increased when shifting the membrane in the positive direction, but there was no evidence for two bursting states. Channel modification by bromate (10 mmol/liter) and glutaraldehyde (0.5 mmol/liter) also included the occurrence of two open states. In contrast to normal Na + channels under control conditions, iodate-modified Na + channels attain two conducting states, a short-lasting one with a voltage-independent lifetime close to 1 msec and, likewise tested between −50 and +10 mV, a long-lasting one being apparently exponentially dependent on voltage. Iodate (10 mmol/liter) removed Na + inactivation and caused repetitive, burst-like channel activity after treating the cytoplasmic channel surface.

Elementary Na + currents were recorded at 19☌ during 220-msec lasting step depolarizations in cell-attached and inside-out patches from cultured neonatal rat cardiocytes in order to study the modifying influence of iodate, bromate and glutaraldehyde on single cardiac Na + channels.

Mv anemona