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Journal of Experimental Biology 149,79-94 (1990)
Published by Company of Biologists 1990

Unitary K⁺ Currents in Growth Cones and Perikaryon of Identified Helix Neurones in Culture

K. A. GREEN ¹, G. B. POWELL ², and A. COTTRELL ²

¹ Department of Biology and Preclinical Medicine, Bute Medical Building, St Andrews University, St Andrews, Fife KY16 9TS, Scotland
² Department of Biology and Preclinical Medicine, Bute Medical Building, St Andrews University, St Andrews, Fife KY16 9TS, Scotland

Unitary potassium (K⁺) currents of several different conductances have been recorded from the growth cones of isolated Cl neurones from Helix aspersa. The isolated neurones were maintained in culture for up to 1 week. Similar unitary currents were recorded in the growth cones of other isolated Helix neurones.

The activity of one type of unitary K⁺ current recorded from the growth cones of the Cl neurone and other neurones was very similar to that described for the S-channel of the perikarya of Aplysia sensory neurones. Another type of unitary K⁺ current showed fast flickering and reduced amplitude when the membrane was held at large positive potentials, which is suggestive of channel block by some agent.

The conductances of the K⁺ channels in the growth cones of isolated Cl neurones were generally smaller than those recorded in this and in previous studies from the perikarya of Cl neurones in situ. However, unitary K⁺ currents recorded from the perikaryon of the Cl neurone, and from other identified neurones, in culture also had lower conductances than those recorded in situ. The mean resting potential of the isolated neurones was smaller than those from neurones in situ. This and other results suggested that reduced intracellular K⁺ concentration in the isolated neurones might be an important factor in deciding the conductance of the recorded channels.

Key words: K⁺ channels, growth cones, multiple conductances, Helix neurones

Accepted on October 25, 1989