Maturation of nerve conduction velocity and the evoked muscle potential in the dog.

Maximum nerve conduction velocity (NCV) of motor fibers in the ulnar nerve was measured in dogs ranging in age from 12 hours after birth to 32 weeks and older. The evoked muscle potential (EMP) resulting from ulnar nerve stimulation was recorded from an interosseous muscle and measured for latency, duration, and amplitude. There was a sharp increase in NCV from 6.3 +/- 0.28 m/s (mean +/- SEM) in dogs from 12 hours to 1 week of age to 59.04 +/- 1.41 m/s in dogs 32 weeks and older. The latency of the EMP, resulting from stimulating the ulnar at either a proximal or a distal site, decreased markedly after birth to 4 to 5 weeks and then more gradually until 10 to 12 weeks. In dogs between 10 to 12 weeks and 32 weeks and older, latency increased but was never as high as in the newborn. Duration of the EMP followed a similar pattern. Amplitude increased sharply with age, resulting in a final 14- to 18-fold increase by 32 weeks and older.