Anomalous potassium channel-gating rates as functions of calcium and potassium ion concentrations.
With near normal monovalent ionic concentrations, the rate of increase of the potassium conductance after a depolarizing voltage-clamp step is slowed when the external calcium concentration is increased. This trend in the rise-time with changes in calcium is reversed when the axointernal potassium concentration is reduced (150 mM) and the periaxonal concentration is increased (50 mM); that is, the rise-time decrease with increasing calcium concentration. Furthermore, the degree of sigmoidality of the K-conductance time-course always increase when the rise-times increase for a given test potential. In the case of calcium surface-charge screening, these effects may be caused by a shifted distribution of K-ions within the channels following the altered ion gradient, and by a consequent shift in the reciprocal electrostatic interactions between the ionic charges and channel-gate charges.
D000818:Animals; D001369:Axons / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D049832:Decapodiformes; D007473:Ion Channels / Q000378:metabolism*; D008433:Mathematics; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*
D007473:Ion Channels; D011188:Potassium; D002118:Calcium