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

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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.