Histological Confirmation of the Bilateral Effect of Unilateral Nerve Injury Detected by 2 H NMR

spectra of injured, control and contralateral rat sciatic nerves. At a creation time of τ=1ms two pairs of quadrupolar split satellites are observed in the control nerve with splittings of about 200 Hz and 500 Hz, which are tentatively assigned to water at the endoneurium and the myelin compartments. The ratio of the intensities of the 200 Hz satellites to the 500 Hz ones was 0.87±0.05 (n=10). Four days after the injury at the proximal end of the sciatic nerve, the intensity ratio for same two pairs of satellites was 1.38±0.30 (n=9). The reduction of the signal associated with the myelin agrees with the damage to the myelin seen in the TEM image (x3000) of the injured nerve. The uninjured contralateral nerve shows very different spectrum than that of the control. The intensity of the 200 Hz satellites is greatly reduced and the ratio between the split signals is 0.38±0.09 (n=7). The TEM image of the contralateral nerve supports this finding, as a much smaller amount of collagen fibers are observed in the endoneurium. Although the myelin layer in the TEM image of the contralateral nerve is different from that of the control, its amount appears to be similar. In another set of experiments, the sciatic nerve was cut in the center of the nerve rather than at the upper end. The resulted damage to the distal part of the injured nerve assessed from the ratio of the two satellites was more significant (1.62±0.22, n=5). No effect on the spectrum of to either the proximal part of the injured nerve (1.03±0.13, n=5) or the contralateral nerve (0.91±0.08, n=5) was observed. Discussion: The assignment of the 500 Hz split signal to the water in the myelin layer is supported by the reduction in both the level of this signal in DQF spectrum and that of myelin tissue in the TEM, in the injured nerve relative to the control. Similarly, the 200 Hz split signal is a reliable representative of the endoneurium component, as seen in the injured nerve as well as in the contralateral nerve. This conclusion is also supported by the MRI experiments that were performed on bovine optic and porcine sciatic nerves. The level of the 200 Hz split signal is barely observed in the spectrum of the optic nerve compared to the sciatic spectrum. This result is in agreement with the smaller amount of endoneurium observed by