EMG changes in rat hind limb muscles following bilateral deafferentation

Bilateral section of dorsal roots was performed in 9 adult rats in order to ascertain whether the tendency to extension, the appearance of spontaneous electromyographic (EMG) activity in extensor muscles and other symptoms of postdenervation hypersensitivity after unilateral deafferentation are not due to the sensory inflow from the contralateral limb. EMG activity from the soleus (SOL) and tibialis anterior (TA) muscles was bilaterally recorded before and at various periods after deafferentation by a previously implanted electrode array. The postural activity in both SOL muscles disappeared after the operation. One to two days later, however, spontaneous tonic EMG activity, similar to that found in the SOL after unilateral deafferentation, appeared in these bilaterally deafferented muscles. The tonic spontaneous EMG activity in hind limb extensor muscles after deafferentation is apparently due to hypersensitivity of spinal neurones to supraspinal influences, since this activity completely disappears after myelotomy. The paradoxical inhibitory EMG response to stretch of the deafferented SOL frequently appeared 1-2 weeks after bilateral dorsal rhizotomy. The performance of movement was highly atactic after bilateral deafferentation. However, the basic locomotor EMG pattern persisted, although simultaneous activation of homonymous muscles was also occasionally recorded.