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    Biophys J. 1992 Jul;63(1):162-8.

    Cadmium block of calcium current in frog sympathetic neurons.

    Source

    Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106.

    Abstract

    Cd2+ blocks whole-cell calcium currents in frog sympathetic neurons by 50% at approximately 300 nM. Strong depolarizations rapidly reverse that blockade (tau = 1.3 ms at +120 mV). Reblocking follows bimolecular kinetics (rate = 1.2 x 10(8) M-1 s-1) at voltages where channels are mostly open (0 to +30 mV). The unblocking rate is approximately 50 s-1, so the dissociation constant calculated from the rate constants is approximately 400 nM. Steady-state block is strong at -80 mV, so closed channels can also be blocked. However, reblocking is extremely slow (tau = 1-2 s) at voltages where the channels are mostly closed. The rates for Cd2+ entry and exit are greater than 100-fold lower for closed channels than for open channels, and closed channels appear to be closed at both ends.

    PMID:
    1330026
    [PubMed - indexed for MEDLINE]
    PMCID:
    PMC1262133
    Free PMC Article

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