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This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 100/1/117    most recent 00829.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Gordon, I. T. Articles by Whelan, P. J. PubMed PubMed Citation Articles by Gordon, I. T. Articles by Whelan, P. J.

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada

Submitted 25 July 2007; accepted in final form 13 April 2008

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 C₅ and C₈ neurograms were each found to be alternating left-right, and the ipsilateral C₅ and C₈ 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 T₅. We next demonstrated that activation of thoracosacral networks either pharmacologically or by stimulation of sacrocaudal afferents could produce rhythmic activity within the C₅ and C₈ 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.