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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 586/10/2487    most recent jphysiol.2007.148320v1 Services Email this article to a friend Similar articles in this journal 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. Related Collections Neuroscience

¹ Hotchkiss Brain Institute
² Department of Physiology & Biophysics
³ Department of Clinical Neurosciences
⁴ Department of Comparative Biology & Experimental Medicine, University of Calgary, Calgary, AB, Canada

During development, descending projections to the spinal cord are immature. Available data suggest that even though these projections are not fully formed, they contribute to activation of spinal circuitry and promote development of network function. Here we examine the modulation of sacrocaudal afferent-evoked locomotor activity by descending pathways. We first examined the effects of brainstem transection on the afferent evoked locomotor-like rhythm using an isolated brainstem–spinal cord preparation of the mouse. Transection increased the frequency and stability of the locomotor-like rhythm while the phase remained unchanged. We then made histologically verified lesions of the ventrolateral funiculus and observed similar effects on the stability and frequency of the locomotor rhythm. We next tested whether these effects were due to downstream effects of the transection. A split-bath was constructed between the brainstem and spinal cord. Neural activity was suppressed in the brainstem compartment using cooled high sucrose solutions. This manipulation led to a reversible change in frequency and stability that mirrored our findings using lesion approaches. Our findings suggest that spontaneous brainstem activity contributes to the ongoing modulation of afferent-evoked locomotor patterns during early postnatal development. Our work suggests that some of the essential circuits necessary to modulate and control locomotion are at least partly functional before the onset of weight-bearing locomotion.

(Received 22 November 2007; accepted after revision 13 March 2008; first published online 27 March 2008)
Corresponding author P. J. Whelan: HSC 2119, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N4N1, Canada. Email: whelan{at}ucalgary.ca