Microinjection into an identified axon to study the mechanism of fast axonal transport.

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Abstract
Microinjection into an axon of an identified invertebrate neuron is a useful technique for analyzing the mechanism of fast axonal transport. It permits direct assessment of the effect of agents that cannot permeate the plasma membrane on the translocation of material in the axon. The actin filament depolymerizer DNase I, when injected into the axon of the Aplysia [california] neuron R2, caused a local block of fast transport of [3H]glycoprotein. Two agents that should interfere with the functioning of actin filaments without causing extensive depolymerization, the N-ethylmaleimide-modified nuclease S1 fragment of myosin (injected) and dihydrocytochalasin B (applied externally), had no effect. Actin probably plays a structural role in the axonal cytoskeleton rather than a role in transport force generation, the effect of DNase I being mediated by structural disordering of the axoplasm. Experiments were also done with inhibitors of dynein, the microtubule-associated ATPase. erythro-9-[3-(2-Hydroxynonyl)]adenine blocked transort, but vanadate was ineffective.