Acute repair of crushed guinea pig spinal cord by polyethylene glycol

We have studied the responses of adult guinea pig spinal cord white matter to a standardized compression within a sucrose gap recording chamber. This injury eliminated compound action potential(CAP) conduction through the les ion, followed by little or no recovery of conduction by 1 h postinjury. We tested the ability of polyethylene glycol (PEG) to repair the injured axons and restore physiological function. Local application of PEG (1,800 MW, 50 % by weight in water) for similar to 2 min restored CAP conduction through the injury as early as 1 min post PEG application. The recovery of the CAP less than or equal to 1 h was significantly greater in treated compared wit h control spinal cords (controls = 3.6% of the preinjury amplitude; PEG tre ated = 19%; P < 0.0001, unpaired Student's t-test). Stimulus-response analy sis indicated that the susceptibility for recovery was similar for all cali bers of axons after PEG application. The enhanced recovery of conduction af ter PEG treatment was associated with an early alteration in conduction pro perties relative to control spinal cords. This included increased refractor iness and sensitivity to potassium channel blockade using 4-aminopyridine ( 4-AP). Normally 4-AP enhanced the amplitude of the recovering CAPs by simil ar to 40% in control spinal cords; however this effect was nearly doubled t o similar to 72% in PEG treated spinal cords. Because severe clinical injur ies to the spinal cord (and some peripheral nerves) are both resistant to m edical treatment and usually produced by compression, we discuss the possib le clinical benefits of PEG application.