Synaptic patterns of thalamocortical afferents in mouse barrels at postnatal day 11.
This study focuses on the synaptic output patterns of thalamocortical axons in mouse barrel cortex at postnatal day (P) 11. Axons were labeled by biotinylated dextran amine transported anterogradely following injection in vivo into the ventrobasal thalamus. Labeled axons in the posteromedial barrel subfield were examined by light and electron microscopy and then reconstructed in three dimensions to assess the spatial distribution of their synapses. Thalamocortical axons form asymmetrical synapses, both at varicosities and along cylindrical portions of the axons; usually, only one synapse occurs per site, contrasting with the case in the adult, in which multiple synapses are typical. At P11, varicosities without synapses are common. As in adult barrels, approximately 80% of synapses formed by thalamocortical axons are with dendritic spines; 20% are with dendritic shafts. The similarity in the distribution of thalamocortical synapses onto spines vs. dendrites in developing and mature barrels indicates that adult synaptic patterns already are specified at a very early stage of thalamocortical synaptogenesis.
Lev
Dmitri L
DL
Department of Morphology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel.
Weinfeld
Elizabeth
E
White
Edward L
EL
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001710:Biotin / Q000031:analogs & derivatives*; D002454:Cell Differentiation / Q000502:physiology*; D048429:Cell Size / Q000502:physiology; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure*; D003911:Dextrans; D005456:Fluorescent Dyes; D007091:Image Processing, Computer-Assisted; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure*; D013003:Somatosensory Cortex / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D020651:Ventral Thalamic Nuclei / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure
D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D001710:Biotin