Laser-induced reconnection of severed axons

After their axons have been severed, nerve cells can achieve functional recovery either by regrowth of the injured cells or by direct repair of the injured cell at the site of injury. Direct repair of a severed axon promises the advantages of preserving the viability and existing connections of the axon distal to the injury. We report here the first successful axon reconnection in the earthworm (Lumbricus terrestris) medial giant axon (MGA) in vitro system (1) by the application of well-focused 15 nsec, 5 to 50 muJ/pulse, 308 nm laser pulses. Axon reconnection is documented by light and electron microscopy, as well as by transfer of the iontophoretically injected fluorescent dye, Lucifer Yellow, across the reconnected MGA segments.