Conduction velocity in peripheral nerve of foetal, newborn and adult sheep.

Measurements have been made of conduction velocity in tibial and peroneal divisions of the sciatic nerve in foetal, newborn and adult sheep. Foetal age ranged from 91 days after mating to term, at 145 days. Measurements on foetuses used chronically implanted electrodes in 6 animals and direct nerve recordings in two acute preparations. For chronic recordings, two pairs of stimulating electrodes were placed as far apart along the nerve as possible and recording electrodes measured the electromyogram of the lateral gastrocnemius muscle. In the nerve recordings stimulating electrodes were placed at several different sites and the latency of the nerve action potential at each site was plotted against electrode separation. Values of maximum conduction velocity in foetal tibial nerve ranged from 24 m/s at 91 days to 60 m/s at term. Conduction velocity increased by 0.6 m/s per day. In the newborn lamb conduction velocity was more than half of the adult value of 96 m/s, indicating the relative maturity of the sheep at birth compared with other mammals.