Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Abstract

Gordon IT, Dunbar MJ, Vanneste KJ, Whelan PJ. Interaction between developing spinal locomotor networks in the neonatal mouse. J Neurophysiol 100: 117-128, 2008. First published April 24, 2008 doi:10.1152/jn.00829.2007. At birth, thoracosacral spinal cord networks in mouse can produce a coordinated locomotor-like pattern. In contrast, less is known about the cervicothoracic networks that generate forelimb locomotion. Here we show that cervical networks can produce coordinated rhythmic patterns in the brain stem-spinal cord preparation of the mouse. Segmentally the C 5 and C 8 neurograms were each found to be alternating left-right, and the ipsilateral C 5 and C 8 neurograms also alternated. Collectively these patterns were suggestive of locomotor-like activity. This pattern was not dependent on the presence of thoracosacral segments because they could be evoked following a complete transection of the spinal cord at T 5 . We next demonstrated that activation of thoracosacral networks either pharmacologically or by stimulation of sacrocaudal afferents could produce rhythmic activity within the C 5 and C 8 neurograms. On the other hand, pharmacological activation of cervical networks did not evoke alternating cervical rhythmic activity either in isolated cervicothoracic or -sacral preparations. Under these conditions, we found that activation of cervicothoracic networks could alter the timing of thoracosacral locomotor-like patterns. When thoracosacral networks were not activated pharmacologically but received rhythmic drive from cervicothoracic networks, a pattern of slow bursts with superimposed fast synchronous oscillations became the dominant lumbar neurogram pattern. Our data suggest that in neonatal mice the cervical CPG is capable of producing coordinated rhythmic patterns in the absence of input from lumbar segments, but caudorostral drive contributes to cervical patterns and rhythm stability.

Endogenous extracellular serotonin modulates the spinal locomotor network of the neonatal mouse

“…A ventral laminectomy exposed the spinal cord sparing as much of the cauda equina as possible, and the ventral and dorsal roots were cut. The brainstem was transected at cranial nerve VII and then the brainstem–spinal cord was gently removed from the vertebral column (Gordon et al 2008). The cerebellum was removed by gently dissecting it away.…”

Effect of cervicolumbar coupling on spinal reflexes during cycling after incomplete spinal cord injury

“…Also in humans, the cadence of leg cycling was not affected by alterations in arm cadence, but involuntary changes in the cadence of arm cycling were seen when leg cycling cadence changed (Sakamoto et al 2007). Taken together, the interaction between cervical and lumbar spinal networks is dynamic and bidirectional, as both rostrocaudal and caudorostral effects were observed (Gordon et al 2008;Thibaudier et al 2013Thibaudier et al , 2017.…”

“…Studies in animals and humans have suggested that the lumbar cord could also regulate the excitability of the cervical cord. Lumbar central pattern generators (CPGs) in isolated neonatal rat spinal cords generated a greater influence on cervical CPGs than the other way around (Gordon et al 2008;Juvin et al 2005Juvin et al , 2012. Also in humans, the cadence of leg cycling was not affected by alterations in arm cadence, but involuntary changes in the cadence of arm cycling were seen when leg cycling cadence changed (Sakamoto et al 2007).…”

A Neonatal Mouse Spinal Cord Injury Model for Assessing Post-Injury Adaptive Plasticity and Human Stem Cell Integration

“…Some have focused, as in adult studies, on behavior and anatomy [19], [20], whereas others have begun to assess the molecular and cellular substrates of recovery, either soon after the injury, at early postnatal stages [21] or much later, in the adult [22]–[24]. The neonatal mouse spinal cord has become a popular preparation for the study of the normal spinal cord circuitry involved in locomotor pattern generation [25]–[27] and in the descending control of spinal motor and autonomic circuits [25], [28]–[32]. The neonatal mouse is amenable to a combination of molecular, genetic, anatomical, physiological, and behavioral approaches to the elucidation of neuronal network organization.…”