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Journal of Experimental Biology 58,15-28 (1973)
Published by Company of Biologists 1973

Potassium Movements in a Central Nervous Ganglion of Limnaea Stagnalis (L.) (Gastropoda:Pulmonata)

D. B. SATTELLE ¹

¹ A.R.C. Unit of Invertebrate Chemistry and Physiology, Department of Zoology, Cambridge

1. Resting potentials and action potentials recorded from in situ, intact and desheathed giant neurones of the right parietal ganglion of Limnaea stagnalis are of similar magnitude. Ganglionic potential profiles reveal the absence of a sheath potential. It is concluded that the extra-neuronal fluid has a similar ionic composition to the blood (bathing medium).

2. A 34 mV decade potassium slope is obtained for both intact and de-sheathed neurones. Depolarization of the neuronal membrane takes place rapidly in intact preparations, and the de-sheathing procedure significantly increases the rate of depolarization.

3. A reduction in temperature from 23 to 8°C only slightly prolongs the time-course of depolarization of an intact neurone. When the concentration of potassium in the fluid bathing the surface of an intact ganglion is elevated, the concentration of this cation at the neuronal surface changes exponentially with time. It is suggested therefore that diffusion along the extracellular channels is the mechanism and pathway for the movement of potassium ions through the right parietal ganglion of Limnaea stagnalis.