The toe-spreading reflex of the rabbit revisited--functional evaluation of complete peroneal nerve lesions

Although a variety of electrophysiological and morphological tests are available for studying nerve regeneration in animals, these endpoints do not necessarily correlate with the return of muscle function. Recent efforts have focused on the assessment of function as the endpoint of nerve regeneration. One of the best known of these tests is the sciatic function index in rats. For rabbits, the toe-spreading reflex has been suggested as a valuable index of peroneal function. We examined the reliability and sensitivity of the toe-spreading reflex in a study of nerve regeneration of the peroneal nerve in 10 New Zealand White rabbits. Eleven weeks after the transection and immediate suturing of the peroneal nerve in both hind legs (at two slightly different sites), a toe-spreading reflex could always be elicited on that side where the level of the severed nerve was closer to the dependent muscles. Also on this hind leg the muscle weight of the peroneal target muscles was significantly higher (P = 0.031) than on the contralateral side, which corresponds well to the results of the toe-spreading reflex. The toe-spreading reflex is an excellent and sensitive indicator of the onset of motor recovery in the peroneal nerve-dependent muscles of rabbits. Even small differences in the localization of lesions in both hind legs can be differentiated with this test.