DISTAL TIBIAL MONONEUROPATHY IN DIABETIC AND NONDIABETIC RATS REARED ON WIRE CAGES - AN EXPERIMENTAL ENTRAPMENT NEUROPATHY

Using electrophysiological recordings, we studied a distal tibial mono neuropathy that involves the hind foot of rats reared in cages with wi re grid flooring. In an initial set of experiments, serial sciatic-tib ial motor conduction recordings were made in smaller or larger rats re ared in cages with wire grid or sawdust flooring. Electrophysiological features of the neuropathy were loss in the amplitude of the distal t ibial nerve M potential recorded over hind limb foot muscles, temporal dispersion of the potential, often into multiple peaks, and a prolong ed distal latency of the response. The changes in M amplitude were mor e apparent in larger rats with a greater body weight. In a second seri es of experiments we studied sciatic-tibial conduction over 16 weeks i n nondiabetic rats and rats rendered diabetic with streptozotocin rais ed and wire grid or plastic flooring. Tibial mononeuropathy developed in both wire grid-reared groups, but there was evidence that it appear ed earlier in diabetic rats. Electrophysiological changes of distal mo noneuropathy also obscured the expected slowing of sciatic-tibial moto r conduction velocity from diabetics. Tibial mononeuropathy in rats re ared on wire grid flooring may be a useful animal model of human entra pment neuropathy but its presence can confound studies of experimental neuropathy. Rats used in studies of experimental neuropathy should be housed in plastic cages with sawdust or shavings flooring.