Nerve orientation may involve a biasing of the distribution of tension at the growth cone. Chemical and electrical guidance cues cause more filopodia to appear on one side of the growth cone and this may determine turning behaviour. In a small applied electric field, filopodia predominate on the cathodal side of the growth cone and nerves turn towards the cathode. Removing all filopodia by treatment with cytochalasin D did not prevent nerves from continued slow growth and nerves still oriented towards the cathode. It is concluded that nerves can perform some types of orienting behaviour in the complete absence of filopodia.

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