[Modulating action of extracellular zinc on transient potassium currents in cerebellar granule cells in the rat]

The effect of Zn2+ 100 microM-1 mM has been studied on the kinetics of the A-current in granule cells from rat cerebellar slices using the patch-clamp technique in the whole-cell configuration. Zn2+ induced marked shifts towards positive potentials of both the activation and inactivation steady-state curves, a reduction of maximal amplitude and a slowing of the activation kinetics, leaving unaffected the inactivation time constants. These modifications cannot be explained in terms of the screening of the negative surface charges, but are probably due to a direct action on the A-channel. The alterations observed in the IA kinetics could be of physiological relevance in some neurological disorders for which significant increase of the Zn2+ levels in the cerebrospinal fluid have been described.