Axonal regeneration with functional restoration in the vestibulospinal tract in young rats

The present study examined regeneration and restoration of function of the mammalian central vestibular system in the infant rat. The lateral vestibulospinal tract (LVST) of rats was completely transected unilaterally by a ventral approach. After a postoperative interval of one day to three months, the LVST was examined by anterograde transport of wheat-germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) and retrograde transport of fluorescent dye. Twelve of the 22 LVST-transected rats showed successful regeneration. The regenerated fibers formed a compact fiber bundle, which sent terminals to their normal targets. The contribution of the regenerated fibers to functional recovery was estimated by analyzing the locomotor capacity of the transected rats. The locomotor movements were measured on the surface of a digitizer table by attaching a miniature resonance coil to the abdomen of the rats. Rats which shows normal locomotor movements represented a marked regeneration of LVST fibers. In contrast, rats with poorly-controlled locomotor movements showed unsuccessful regeneration. These results suggest that, contrary to previous thought, regeneration and functional restoration of the central vestibular system in young rats does occur.