Spatiotemporal pattern of motoneuron activation in the rostral lumbar and the sacral segments during locomotor-like activity in the neonatal mouse spinal cord.
We used calcium imaging to visualize the spatiotemporal pattern of motoneuron activity during dorsal root-evoked locomotor-like bursting in the lumbosacral spinal cord of the neonatal mouse. Dorsal root stimuli elicited a tonic discharge in motoneurons on which alternating left-right rhythmic discharges were superimposed. Both the tonic and the rhythmic components could be recorded optically from populations of motoneurons labeled with calcium-green dextran. Optical and electrical recordings revealed that rhythmic signals from different parts of the lumbar (L1, L2) and sacral (S1-S3) segments rose, peaked, and decayed in a rostrocaudal sequence. This pattern gave rise to a rostrocaudal "wave" in the activation of motoneurons during each cycle of locomotor-like activity. A similar rostrocaudal delay was observed during episodes of alternation that occurred in the absence of stimulation, suggesting that this delay was not caused by the train of dorsal root stimuli. It is hypothesized that this behavior may simplify the appropriate sequencing of motoneurons during locomotion.
Bonnot
Agnès
A
Laboratory of Neural Control, Section on Developmental Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA. bonnota@ninds.nih.gov
Whelan
Patrick J
PJ
Mentis
George Z
GZ
O'Donovan
Michael J
MJ
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D005727:Ganglia, Spinal / Q000502:physiology; D066298:In Vitro Techniques; D020407:Internet; D008161:Lumbosacral Region / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000378:metabolism*; D010507:Periodicity; D013116:Spinal Cord / Q000502:physiology*; D014741:Video Recording
D005456:Fluorescent Dyes; D002118:Calcium