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The Journal of Neuroscience, April 15, 2009, 29(15):5032-5043; doi:10.1523/JNEUROSCI.5331-08.2009

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Development/Plasticity/Repair
Type A GABA-Receptor-Dependent Synaptic Transmission Sculpts Dendritic Arbor Structure in Xenopus Tadpoles In Vivo

Wanhua Shen,^1,2 * Jorge Santos Da Silva,^1 * Haiyan He,^1,2 and Hollis T. Cline^1,2

¹Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, and ²The Scripps Research Institute, La Jolla, California 92037

Correspondence should be addressed to Hollis T. Cline, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037. Email: cline{at}scripps.edu

The emergence of dendritic arbor structure in vivo depends on synaptic inputs. We tested whether inhibitory GABAergic synaptic transmission regulates Xenopus optic tectal cell dendritic arbor development in vivo by expressing a peptide corresponding to an intracellular loop (ICL) of the 2 subunit of type A GABA receptors (GABA_AR), which is required to anchor GABA_A receptors to the postsynaptic scaffold. Enhanced green fluorescent protein (EGFP)-tagged ICL (EGFP-ICL) was distributed in a punctate pattern at putative inhibitory synapses, identified by vesicular GABA transporter immunoreactive puncta. ICL expression completely blocked GABA_AR-mediated transmission in 36% of transfected neurons and significantly reduced GABA_AR-mediated synaptic currents relative to AMPA receptor-mediated synaptic currents in the remaining transfected neurons without altering release probability or neuronal excitability. Further analysis of ICL-expressing neurons with residual GABA_AR-mediated inputs showed that the capacity of benzodiazepine to enhance GABAergic synaptic responses was reduced in ICL-expressing neurons, indicating that they were likely depleted of 2 subunit-containing GABA_AR. Neurons expressing a mutant form of ICL were comparable to controls. In vivo time-lapse images showed that ICL-expressing neurons have more sparsely branched dendritic arbors, which expand over larger neuropil areas than EGFP-expressing control neurons. Analysis of branch dynamics indicated that ICL expression affected arbor growth by reducing rates of branch addition. Furthermore, we found that decreasing GABAergic synaptic transmission with ICL expression blocked visual experience dependent dendritic arbor structural plasticity. Our findings establish an essential role for inhibitory GABAergic synaptic transmission in the regulation of dendritic structural plasticity in Xenopus in vivo.

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Received Nov. 5, 2008; revised Feb. 12, 2009; accepted March 12, 2009.

Correspondence should be addressed to Hollis T. Cline, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037. Email: cline{at}scripps.edu

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				C. Mason The Development of Developmental Neuroscience J. Neurosci., October 14, 2009; 29(41): 12735 - 12747. [Full Text] [PDF]

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