Electrically mediated regeneration and guidance of adult mammalian spinal axons into polymeric channels
Section snippets
The implant
The constant-current (d.c.) implant consisted of two components: the stimulator and a hollow silicone rubber guidance channel containing an active negative electrode (the cathode) or a sham electrode within its center.
The stimulator was similar to previously reported designs11., 15., 17. using one 3-V Lithium Cell (Ray o Vac 1225 BR) connected to a constant-current source (National Semiconductor LM 334 Z), which regulates the d.c. output, and a one-eighth-watt resistor to set the total current
General procedure
Animals tolerated the surgical procedures well, and the minor mortality was not significantly different between the experimental and control groups. All stimulator units were functional at the time of their removal (the battery would not be exhausted for another week or more of continuous operation). Although both ends of the tube were visually confirmed to be imbedded in the parenchyma of the spinal cord at surgery, in five cases (four control, one experimental), one end worked out of the cord
Discussion
This report demonstrates that a weak electric field imposed within a damaged adult guinea-pig spinal cord can both induce the regeneration of axons, and guide their growth, into the ends of a hollow silicone rubber tube inserted into the dorsal half of the cord. This is because a pair of electrodes produced a d.c. voltage gradient within the injured spinal cord, with the cathode located within the experimental tubes. This negative electrode drew current into the open ends of the tubes,
Acknowledgements
I dedicate this work to the memory of Professor Melvin Cohen of Yale University, mentor and friend. I gratefully acknowledge the expert technical assistance of Aaron Harbath for stimulator fabrication, Debra Bohnert for expert surgery and preparation of the tissues for analysis and viewing, and Andrea Street and Jenifer Sanson for manuscript preparation. David Williams provided the artwork used in the Experimental Procedures section. This work was supported by a grant from the Public Health
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