On the Mechanism of Nerve Galvanotropism

¹ Department of Physiology, Marischal College, University of Aberdeen, Aberdeen AB9 1AS, Scotland

The mechanism whereby nerves turn towards the cathode in a small applied electric field has been investigated. The distribution of filopodia on the growth cone is suggestive of a pivotal role in orientation. However, nerves denuded of all filopodia by treatment with cytochalasin D continued to grow and to turn towards the cathode. Nerves treated with neuraminidase showed robust galvanotropic responses, which may call into question the role of cell surface receptor redistribution in orientation. The calcium channel blocker cobalt inhibited orientation, while simultaneous treatment of nerves with cobalt and the calcium ionophore A23187 resulted in nerves turning towards the anode; a reversal of galvanotropism. Localized entry of calcium, predominantly on one side of the growth cone, may underlie galvanotropism.