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This Article Full Text Full Text (PDF) All Versions of this Article: 586/6/1623    most recent jphysiol.2007.148361v1 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 Cowley, K. C. Articles by Schmidt, B. J. PubMed PubMed Citation Articles by Cowley, K. C. Articles by Schmidt, B. J. Related Collections Neuroscience

¹ Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3J7

We recently showed that propriospinal neurons contribute to bulbospinal activation of locomotor networks in the in vitro neonatal rat brainstem–spinal cord preparation. In the present study, we examined whether propriospinal neurons alone, in the absence of long direct bulbospinal transmission to the lumbar cord, can successfully mediate brainstem activation of the locomotor network. In the presence of staggered bilateral spinal cord hemisections, the brainstem was stimulated electrically while recording from lumbar ventral roots. The rostral hemisection was located between C1 and T3 and the contralateral caudal hemisection was located between T5 and mid-L1. Locomotor-like activity was evoked in 27% of the preparations, which included experiments with staggered hemisections placed only two segments apart. There was no relation between the likelihood of developing locomotor-like activity and the distance separating the two hemisections or specific level of the hemisections. In some experiments, where brainstem stimulation alone was ineffective, neurochemical excitation of propriospinal neurons (using 5-HT and NMDA) at concentrations subthreshold for producing locomotor-like activity, promoted locomotor-like activity in conjunction with brainstem stimulation. In other experiments, involving neither brainstem stimulation nor cord hemisections, the excitability of propriospinal neurons in the cervical and/or thoracic region was selectively enhanced by bath application of 5-HT and NMDA or elevation of bath K⁺ concentration. These manipulations produced locomotor-like activity in the lumbar region. In total, the results suggest that propriospinal neurons are sufficient for transmission of descending locomotor command signals. This observation has implications for regeneration strategies aimed at restoration of locomotor function after spinal cord injury.

(Received 16 November 2007; accepted after revision 28 January 2008; first published online 31 January 2008)
Corresponding author B. J. Schmidt: Department of Physiology, Room 406, Basic Medical Sciences Bldg, University of Manitoba, 730 William Avenue, Winnipeg, Manitoba, Canada R3E 3J7.  Email: brian{at}scrc.umanitoba.ca