Interplay between laminar specificity and activity-dependent mechanisms of thalamocortical axon branching.
Target and activity-dependent mechanisms of axonal branching were studied in the thalamocortical (TC) projection using organotypic cocultures of the thalamus and cortex. TC axons were labeled with enhanced yellow fluorescent protein (EYFP) by a single-cell electroporation method and observed over time by confocal microscopy. Changes in the firing activity of cocultures grown on multielectrode dishes were also monitored over time. EYFP-labeled TC axons exhibited more branch formation in and around layer 4 of the cortical explant during the second week in vitro, when spontaneous firing activity increased in both thalamic and cortical cells. Time-lapse imaging further demonstrated that branching patterns were generated dynamically by addition and elimination with a bias toward branch accumulation in the target layer. To examine the relationship between neural activity and TC branch formation, the dynamics of axonal branching was analyzed under various pharmacological treatments. Chronic blockade of firing or synaptic activity reduced the remodeling process, in particular, branch addition in the target layer. However, extension of branches was not affected by this treatment. Together, these findings suggest that neural activity can modify the molecular mechanisms that regulate lamina-specific TC axon branching.
Uesaka
Naofumi
N
Neuroscience Laboratories, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
Hayano
Yasufumi
Y
Yamada
Akito
A
Yamamoto
Nobuhiko
N
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001426:Bacterial Proteins / Q000235:genetics; D002450:Cell Communication; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology* / Q000502:physiology; D018920:Coculture Techniques; D003463:Cues; D018274:Electroporation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D020439:Growth Cones / Q000502:physiology* / Q000648:ultrastructure; D008164:Luminescent Proteins / Q000235:genetics; D018613:Microscopy, Confocal; D009434:Neural Pathways / Q000166:cytology / Q000196:embryology* / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013194:Staining and Labeling / Q000379:methods; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013788:Thalamus / Q000166:cytology / Q000196:embryology* / Q000502:physiology
D001426:Bacterial Proteins; D018691:Excitatory Amino Acid Antagonists; D008164:Luminescent Proteins; D026941:Sodium Channel Blockers; C054562:yellow fluorescent protein, Bacteria