TY - JOUR T1 - Interplay between Laminar Specificity and Activity-Dependent Mechanisms of Thalamocortical Axon Branching JF - The Journal of Neuroscience JO - J. Neurosci. SP - 5215 LP - 5223 DO - 10.1523/JNEUROSCI.4685-06.2007 VL - 27 IS - 19 AU - Naofumi Uesaka AU - Yasufumi Hayano AU - Akito Yamada AU - Nobuhiko Yamamoto Y1 - 2007/05/09 UR - http://www.jneurosci.org/content/27/19/5215.abstract N2 - 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. ER -