Linear analysis ofKconduction in snail neuron from impedance determinations

Publisher Website
Google Scholar
Abstract
The complex impedance of a soma cell membrane in an identified, isolated single neuron from Helix aspersa (snail) was measured in the frequency range 0.25 Hz to 100 Hz in order to quantify the electrical properties and kinetics of potassium conduction. Use of a synchronized Fourier-synthesized signal applied as a small perturbation during step current-source stimulation via an external suction capillary and use of an internal microelectrode to record the voltage response permitted rapid (4 sec) acquisition of a 400-point impedance function of frequency. Three types of potassium conductance were distinguishable pharmacologically in complex impedance determinations. The linear kinetic parameters of two types of K conductance, the voltage-sensitive “delayed rectifier” potassium conductance, and the Ca-activated, potassium conductance were obtained by curve fitting model admittance functions of frequency to complex admittances obtained from the reciprocal of measured steady-state impedance data. Time constants of activation of voltage-sensitive “delayed rectifier” potassium conductance are in the range between 14.7 msec at a membrane potential of −40 mV and 6.0 msec at 0 mV. The kinetics of K conductance relaxations were evident in the frequency domain functions with behavior analogous to that of a resistance-inductance (RL) circuit. The time constants of activation of Ca-activated potassium conductance lie between 108 msec at a membrane potential of −40 mV and 65.7 msec at 10 mV. At hyperpolarized voltages in high external potassium, a third type of K conductance was manifested by a small amount of rectification of inward potassium current.

This publication has 15 references indexed in Scilit: