NEURITES GROW FASTER TOWARDS THE CATHODE THAN THE ANODE IN A STEADY-FIELD

We explanted fragments of embryonic chick dorsal root ganglia on to polylysine coated glass and cultured them in a medium containing one unit of nerve growth factor plus enough methylcellulose to give viscosities from 0.01–3,000 poise. We allowed them to grow out in the absence of a field, and then selected explants with halos of neurites which were relatively dense, relatively symmetrical, and practically free of glial cells. These selected explants were then exposed to electrical fields of up to 140 mV/mm for some hours. In media with viscosities of one poise or less, the field some times dragged the central cell mass of an explant towards the anode. However, in cases where the central cell mass did notmove, fields of 70–140 m V/mm induced that sector of each neurite halo which faced the cathode to grow out several times faster than the one facing the anode. This neurite growth response showed little or no dependence upon viscosity (although it was inhibited by movements of the central cell mass). We speculate that it is mediated by lateral electrophoresis of the receptors for nerve growth factor along the plasma membranes of the neurites. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company