Functional reconnection of severed mammalian spinal cord axons with polyethylene glycol

We describe a technique using the water-soluble polymer polyethylene glycol (PEG) to reconnect the two segments of completely transected mammalian spi nal axons within minutes. This was accomplished by fusing completely severe d strips of isolated guinea pig thoracic white matter maintained in vitro i n a double sucrose gap recording chamber, The faces of the severed segments were pressed together, and PEG (MW 1,400-3,500 d; similar to 50% by weight in distilled water) was applied directly to this region through a micropip ette and removed by aspiration within 2 min. Successful fusion was document ed by the immediate restored conduction of compound action potentials throu gh the original transection and by the variable numbers of fused axons in w hich anatomical continuity was shown to be restored by high-resolution ligh t microscopy and by the diffusion of intracellular fluorescent dyes through fused axons, These data support the conclusion that some severed and subse quently PEG-fused spinal axons both demonstrate restored anatomical continu ity and also are physiologically competent to conduct action potentials. Th is work adds to our previous demonstration that PEG application can immedia tely repair severely crushed, rather than cut, spinal cord white matter, an d may lead to novel treatments for acute trauma to the central and peripher al nervous systems.