The Spinal Transmission of Proprioceptive Reflexes and the Postnatal Development of Conduction Velocity in Different Hindlimb Nerves in the Kitten

Abstract

Abstract The postnatal development of the conduction velocity in different nerves of the hindlimb has been investigated in the kitten from birth to 4 months of age. It is found that the different fibre systems which have about the same conduction velocity at birth, with reference to conduction velocity, develop at different rates. Thus the large muscle afferents and efferents develop faster than the large fibres of the skin nerves and the latter faster than the gamma efferents. The conduction velocities reach adult values 3.5‐4 months after birth. It is also shown that proprioceptive reflexes can be mediated by arcs of two neurons in the newborn kitten. Furthermore the reflex time for the two‐neuron arc attains adult values when the conduction velocity of the fastest muscle afferents reaches 30 m/sec, which occurs around 20 days postnatally.