Subthreshold and near‐threshold membrane currents in lobster stretch receptor neurones.

Abstract

The ionic currents in the slowly and rapidly adapting stretch receptor neuron of the lobster were investigated with respect to their nature and stationary kinetics in sub- and near-threshold voltage regions using electrophysiological and pharmacological techniques. In both neurons the currents identified were: a tetrodotoxin-sensitive Na current; a tetraethylammonium and 4-aminopyridine-sensitive K current; a Co (or Mn)-sensitive Ca-dependent K current; an ouabain-sensitive pump current and a remaining leak current carried mainly by Na, K and Cl. In suprathreshold voltage regions the balance between the individual membrane currents leads to the formation of a stationary negative conductance (negative slope in the voltage dependence of the ionic current) in the slowly, but not in the rapidly adapting cell. During prolonged suprathreshold stimulation a stationary low frequency impulse firing is possible in the slowly adapting cell, whereas in the rapidly adapting cell it is not.