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1: J Neurosci. 2009 Apr 15;29(15):5032-43. Links
Type A GABA-receptor-dependent synaptic transmission sculpts dendritic arbor structure in Xenopus tadpoles in vivo. Shen W, Da Silva JS, He H, Cline HT.
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Theemergence of dendritic arbor structure in vivo depends on synapticinputs. We tested whether inhibitory GABAergic synaptic transmissionregulates Xenopus optic tectal cell dendritic arbor development in vivoby expressing a peptide corresponding to an intracellular loop (ICL) ofthe gamma2 subunit of type A GABA receptors (GABA(A)R), which isrequired to anchor GABA(A) receptors to the postsynaptic scaffold.Enhanced green fluorescent protein (EGFP)-tagged ICL (EGFP-ICL) wasdistributed in a punctate pattern at putative inhibitory synapses,identified by vesicular GABA transporter immunoreactive puncta. ICLexpression completely blocked GABA(A)R-mediated transmission in 36% oftransfected neurons and significantly reduced GABA(A)R-mediatedsynaptic currents relative to AMPA receptor-mediated synaptic currentsin the remaining transfected neurons without altering releaseprobability or neuronal excitability. Further analysis ofICL-expressing neurons with residual GABA(A)R-mediated inputs showedthat the capacity of benzodiazepine to enhance GABAergic synapticresponses was reduced in ICL-expressing neurons, indicating that theywere likely depleted of gamma2 subunit-containing GABA(A)R. Neuronsexpressing a mutant form of ICL were comparable to controls. In vivotime-lapse images showed that ICL-expressing neurons have more sparselybranched dendritic arbors, which expand over larger neuropil areas thanEGFP-expressing control neurons. Analysis of branch dynamics indicatedthat ICL expression affected arbor growth by reducing rates of branchaddition. Furthermore, we found that decreasing GABAergic synaptictransmission with ICL expression blocked visual experience dependentdendritic arbor structural plasticity. Our findings establish anessential role for inhibitory GABAergic synaptic transmission in theregulation of dendritic structural plasticity in Xenopus in vivo.
PMID: 19369572 [PubMed - in process] |
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