Identification of CNS neural circuitry involved in the innervation of C7 spinal nerve: a viral transsynaptic tracing study

ObjectiveContralateral C7 spinal nerve transfer is a useful operation for the treatment of brachial plexus root avulsion. The recovery of the independent function at the ipsilateral side, however, depends on neural circuitry reorganization in the central nervous system (CNS). This study tried to locate the CNS neuronal elements involved in the innervation of C7 spinal nerve.MethodPseudorabies virus (PRV, TK/gG-, 2 Ld), which expressed green fluorescent protein (GFP), was injected into the left C7 spinal nerve in 20 adult Sprague Dawley rats. After rats survived for 6 h, 12 h, 24 h and 36 h, the CrC7 segments of the spinal cord and brain were processed using a polyclonal immunohistochemical antibody against PRV.ResultsPRV-labeled neurons were found mainly in gray matter of the C1-C7 segments of the spinal cord and at the following structures of the brain: lateral vestibular nucleus, lateral paragigantocellular nucleus, A5 cells, red nucleus, primary and secondary motor cortexes, primary and secondary somatosensory cortexes. Although located bilaterally, the PRV-labeled neurons existed predominantly in the ipsilateral side of the spinal cord and the contralateral side of the brain at 6-12 h after injection (p.i.). The number of PRV-labeled neurons in the CNS was increasing with rat’s survival time and the distribution of these neurons turned bilateral with no obvious dominance to either side at 24 h and 36 h (p.i.).ConclusionBy use of transsynaptic tracing technique with PRV, the anatomically connected set of neurons, which modulates the activity of C7 spinal nerve, is located successfully in the CNS.