Loss and spontaneous recovery of forelimb evoked potentials in both the adult rat cuneate nucleus and somatosensory cortex following contusive cervical spinal cord injury

Abstract

Varying degrees of neurologic function spontaneously recovers in humans and animals during the days and months after spinal cord injury (SCI). For example, abolished upper limb somatosensory potentials (SSEPS) and cutaneous sensations can recover in persons post-contusive cervical SCI. To maximize recovery and the development/evaluation of repair strategies, a better understanding of the anatomical locations and physiological processes underlying spontaneous recovery after SCI is needed. As an initial step, the present study examined whether recovery of upper limb SSEPs after contusive cervical SCI was due to the integrity of some spared dorsal column primary afferents that terminate within the cuneate nucleus and not one of several alternate routes. C5-C6 contusions were performed on male adult rats. Electrophysiological techniques were used in the same rat to determine forelimb evoked neuronal responses in both cortex (SSEPS) and the cuneate nucleus (terminal extracellular recordings). SSEPs were not evoked 2 days post-SCI but were found at 7 days and beyond, with an observed change in latencies between 7 and 14 days (suggestive of spared axon remyelination). Forelimb evoked activity in the cuneate nucleus at 15 but not 3 days post-injury occurred despite dorsal column damage throughout the cervical injury (as seen histologically). Neuroanatomical tracing (using 1% unconjugated cholera toxin B subunit) confirmed that upper limb primary afferent terminals remained within the cuneate nuclei. Taken together, these results indicate Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access

Multi-limb acquisition of motor evoked potentials and its application in spinal cord injury

“…While there have been many studies which use either MEPs (Cao et al, 2005;García-Alías et al, 2006;Beaumont et al, 2009) or SSEPs (Nagai et al, 2006;Onifer et al, 2007a;Nakashima et al, 2008;Saadoun et al, 2008;Agrawal et al, 2009b) to characterize SCI, fewer studies use both methods and record MEPs and SSEPs from the same rat before and after SCI. Concurrent measurement of SSEPs and MEPs is possible using the set-up described in this paper.…”

Plasticity After Spinal Cord Injury: Relevance to Recovery and Approaches to Facilitate It

“…The contributions of plasticity to functional return and recovery are hard to discriminate from other possible processes including the recovery from spinal shock and the effect of spontaneous remyelination of spared, but demyelinated axons (eg, see [4]). As for spinal shock, the neuronal mechanism is only vaguely known and could involve the breakdown of membrane potentials, excessive neurotransmitters levels, and the loss of neuromodulators regulating the excitability in the spinal cord [5].…”

The efficacy of antioxidants in functional recovery of spinal cord injured rats: an experimental study

“…Attempts to overcome local barriers by grafting peripheral nerve bridges, Schwann cells or olfactory ensheathing cells [10][11][12] have led to regenerative fiber growth and in some instances to behavioral recovery in animal models of SCI, although the mechanistic understanding of this recovery remains incomplete because of the complexity of these interventions. Varying degrees of neurologic function spontaneously recovers in humans and animals during the days and months after SCI [13]. Several animal models of SCI have been developed in recent years, which have significantly advanced our understandings of pathophysiology of this condition [14].…”