THE DEVELOPMENTAL SKELETAL GROWTH IN THE RAT FOOT IS REDUCED AFTER DENERVATION

It has long been known that bone is innervated. In recent years it has been suggested that the local nerves may influence the growth and met abolism of bone by way of neuropeptides. The transient local presence of nerve-containing cartilage canals just before formation of secondar y ossification centres in rat knee epiphyses seems to support that vie w. The purpose of the present study was to see if denervation affects the developmental growth of metatarsal bones in the rat hindfoot. We m ade sciatic and femoral neurectomies in 7- day-old rat pups and examin ed the hindfeet at various times after surgery. Immunohistochemical an alysis showed that denervation was complete. Radiographic examination revealed that the metatarsal bones were significantly shorter in dener vated hindfeet 30 days after denervation (average relative shortening 9.9+/-2.3%). Measurements of total foot length showed that denervated feet were subnormally sized already five days postoperatively, before the onset of secondary ossification. The timing of the latter was not affected by denervation. Control rats subjected to tenotomies exhibite d normal metatarsal bone lengths. On the basis of these results we sug gest that the local nerves may influence the growth of immature bones but do not affect secondary ossification.