Anisotropic and restricted diffusion of water in the sciatic nerve: A H-2 double-quantum-filtered NMR study

The signals of water in the different compartments of rat sciatic nerve are resolved in the H-2 double-quantum-filtered NMR spectrum, due to their dif ferent quadrupolar splittings and relaxation rates, This resolution allowed the independent measurement of the water diffusion coefficients in the dif ferent compartments. The water diffusion in all three compartments, the end oneurium, the epineurium and the axon was found to be anisotropic, Parallel to the nerve fiber the average intraxonal water diffusion coefficient was 1.11 x 10(-5) cm(2)/sec, while in the perpendicular direction the diffusion is heavily restricted. The average perpendicular diffusion coefficient ran ged from 0.29 x 10(-5) cm(2)/sec to 0.05 x 10(-5) cm(2)/sec for diffusion t imes of 7 msec and 50 msec, respectively, Assuming restricted diffusion in nonpermeable cylinders, intra-axonal mean diameters of 6.0, 7.4 and 9.0 mu m were obtained for nerves taken from three different rats. (C) 1999 Wiley- Liss, Inc.