Document Detail

Cell death of motoneurons in the chick embryo spinal cord. X. Synapse formation on motoneurons following the reduction of cell death by neuromuscular blockade.
MedLine Citation:
PMID:  2754434     Owner:  NLM     Status:  MEDLINE    
Chronic treatment of chick embryos with neuromuscular blocking agents, such as curare, rescues motoneurons from naturally occurring cell death. In the present study, embryos treated with curare from E6 to E9 had 35% more motoneurons than controls on E10 and 42% more than controls on E16. Previous studies have shown that several aspects of motoneuron differentiation occur normally in curare-treated embryos. We report here that dendrite growth and arborization is also unaltered on E10 and E16 following curare treatment. A quantitative analysis of afferent synapses on motoneurons shows that the packing density of both axosomatic and axodendritic synapses is also normal on E10 in curare-treated embryos, despite the greater number of motoneurons present. This indicates that the interneurons that provide presynaptic input to motoneurons are able to compensate for the increased number of synaptic sites made available by curare treatment. However, by E16 the packing density of synapses is reduced by about half. Because motoneurons and their dendrites continue to grow between E10 and E16, the further increase in synaptic sites made available in curare-treated embryos apparently exceeds the compensatory capacity of presynaptic interneurons on E16. One can conclude from these results that the increased survival of motoneurons in curare-treated embryos is not owing to an increase in afferent synapses. Motoneurons in these embryos continue to survive in the face of either no change (E10) or a reduction (E16) in the number of axodendritic and axosomatic synapses. Therefore, increased motoneuron survival in this situation is very likely regulated primarily by motoneuron-target interactions.
A Okada; S Furber; N Okado; S Homma; R W Oppenheim
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurobiology     Volume:  20     ISSN:  0022-3034     ISO Abbreviation:  J. Neurobiol.     Publication Date:  1989 Jun 
Date Detail:
Created Date:  1989-09-05     Completed Date:  1989-09-05     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0213640     Medline TA:  J Neurobiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  219-33     Citation Subset:  IM    
Department of Anatomy, Nihoun University, Tokyo, Japan.
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MeSH Terms
Axons / drug effects,  ultrastructure
Cell Survival / drug effects
Chick Embryo
Dendrites / drug effects,  ultrastructure
Microscopy, Electron
Motor Neurons / cytology,  drug effects,  physiology*
Reference Values
Spinal Cord / cytology,  drug effects,  embryology*
Synapses / drug effects,  physiology*
Tubocurarine / pharmacology*
Grant Support
Reg. No./Substance:

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