Rat motor neuron plasticity induced by dorsal rhizotomy

The control of peripheral structural plasticity of motor neurons by primary sensory neurons was studied in rat extensor digitorum longus (EDL) muscle. Polyinnervation of muscle fibers, sprouting and the motor neuron periphera l field size following L4 dorsal root cutting were evaluated using three di fferent approaches: intracellular recording of end plate potentials, histoc hemical demonstration of sprouting and polyinnervation and in vivo recordin g of nerve-evoked twitch. Nodal sprouting was found in rhizotomized rats bu t not in controls and consistently muscle polyinnervation appeared. The mus cle portion innervated by L3 ventral root was relatively reduced and that i nnervated by L5 was relatively enlarged: a trend to caudal shift of muscle innervation arose in rhizotomized rats. A control of motor neuron plasticit y by primary sensory neurons is suggested. (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.