Restitution of functional neural connections in chick embryos assessed in vitro after spinal cord transection in Ovo.
Functional neural reconnection is not common after spinal cord transection in the CNS of adult higher vertebrates but has been demonstrated in embryonic avian and neonatal mammalian CNS. Chick brainstem spinal cord preparations from nontransected controls and embryos transected at the cervical level on embryonic days (E) 8, 9, or 10 in ovo were assessed in vitro between E12 and E20 for their ability to produce and maintain episodic motor activity (EMA) using electrophysiological, voltage sensitive dye and anatomical tract-tracing techniques. After 3 to 4 days recovery, cycle-by-cycle coupling of EMA between segments separated by a transection was absent or inconsistent, although otherwise normal bouts of locally stimulated and spontaneous EMA were routinely observed restricted to segments of a cord separated by a transection site. After 5-7 days recovery in ovo the cross-transection coordination during bouts of EMA approached that of nontransected controls. The delay between the initiation of EMA in cervical segments to its initiation in lumbosacral segments caudal to a transection was an indicator of reconnection strength. The delay shortened from 0.5 to a few seconds after 3 days of recovery to around 150 ms (i.e., normal) after 5 days of recovery. We conclude that the reconnection of spinal central pattern generators for EMA across the transection was served mainly by axons which established connections with local circuits after extending 1-3 segments through a transection. Propriospinal axons that originated within 1-3 segments rostral to the transection then served to serially initiate EMA in distal caudal segments.
Sholomenko
G N
GN
Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., V5A 1S6, Canada.
Delaney
K R
KR
D000818:Animals; D001933:Brain Stem / Q000166:cytology* / Q000196:embryology*; D002642:Chick Embryo; D004396:Coloring Agents; D003714:Denervation; D004558:Electric Stimulation; D004594:Electrophysiology; D006735:Horseradish Peroxidase; D007552:Isotonic Solutions / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways; D010063:Ovum; D012032:Refractory Period, Electrophysiological / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology* / Q000196:embryology* / Q000601:surgery; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D004396:Coloring Agents; D007552:Isotonic Solutions; C037692:Tyrode's solution; D006735:Horseradish Peroxidase