Modulation of Sodium Channel Activity in Frog Ventricular Cells by Guanidyl-side Armed Cyclam

Yakehiro Masuhide

Hiroshima Journal of Medical Sciences

[PISSN] 0018-2052

[EISSN] 2433-7668

[NCID] AA00664312

The mechanism underlying the Na channel blocking action of guanidyl-side armed cyclam (G-cyclam) was studied using conventional patch-clamp methods. G-cyclam applied to the cytoplasmic surface of the membrane reduced the amplitude of single Na channel currents without inducing a flickering block. This effect was enhanced by depolarization and was fully reversible upon washout of the drug. The relationship between the concentration of G-cyclam and the reduction of unitary current could be expressed mathematically assuming one-to-one stoichiometry. During maximal suppression of the single channel current by G-cyclam approximately 40% of the current remained. Low concentration of G-cyclam (3×10-4M) prolonged, while higher concentration (3×10-3M) shortened the mean open time suggesting the involvement of two processes in the Na channel blocking action of this agent. It appears that low concentration of G-cyclam induce rapid and frequent transition between open and less conductive state resulting in a reduced current, and higher concentration make the channel nonconductive with slower single channel kinetics.

Sodium channel

Polyamine

Frog ventricular cells

Block

Medical sciences [ 490 ]

eng

Hiroshima University Medical Press

[ISSN] 0018-2052

[NCID] AA00664312

[PMID] 1338064