ABSTRACT
Rapid axonal depolarization follows the elevation of [K+]o in the Ringer bathing the surfaces of the connectives of both intact and desheathed cerebro-visceral connectives of Anodonta cygnea. Potassium movements between the blood or medium bathing the surface of the connectives and the axonal membranes can be accounted for in terms of a first-order diffusion process. No visible structural barriers to prevent free movements of materials through the neural lamella and the extracellular spaces can be detected in electron micrographs of the cerebro-visceral connectives. In desheathed preparations fast action potentials are conducted in sodium-free (dextran) Ringer. Mechanisms of axonal function and ionic regulation in this and other inverte-brate central nervous tissues are discussed in the light of these observations.
