Motor impairment after unilateral hind limb deafferentation in young rats

Unilateral section of dorsal roots L2-L6(S1) was performed in 45 rats during the early postnatal period (2 to 12 days postnatally). There was a high mortality rate, especially in the youngest age groups. Behavioural observations (9 rats) and chronic EMG recordings (4 rats) in both soleus and tibialis anterior muscles after implantation of the recording array at the age of 3-4 months led to the following findings: a) the deafferented hind limbs exhibited a tendency to extension similar to that after deafferentation in adult animals; b) there was spontaneous EMG activity in the deafferented soleus muscle; c) the paradoxical reaction of deafferented extensor muscles to stretch could occasionally be demonstrated; d) although the performance of walking was highly atactic, the EMG pattern of ambulation appeared to be normal. These results indicate that deafferentation performed in rats at an early postnatal period evokes similar symptoms as deafferentation in adult animals. Furthermore, early unilateral dorsal root section performed before the maturation of an adult-like pattern of walking does not prevent the development of a normal EMG pattern of ambulation.