Compartmentalization of GABAergic Inhibition by Dendritic Spines

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Science  10 May 2013:
Vol. 340, Issue 6133, pp. 759-762
DOI: 10.1126/science.1234274

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Dendritic Precision Strikes

The effects of excitatory synaptic inputs are considered to be highly compartmentalized because of the biophysical properties of dendritic spines. Individual inhibitory synapses, however, are thought to affect dendritic integration in a more extended spatial region. Combining optogenetic stimulation of dendrite-targeting γ-aminobutyric acid—mediated interneurons with two-photon calcium imaging in postsynaptic pyramidal cell dendrites, Chiu et al. (p. 759) challenge this latter view. The findings suggest that the effect of an inhibitory synapse can be as compartmentalized as that of an excitatory synapse, provided that the synapses are localized on spine heads.


γ-aminobutyric acid–mediated (GABAergic) inhibition plays a critical role in shaping neuronal activity in the neocortex. Numerous experimental investigations have examined perisomatic inhibitory synapses, which control action potential output from pyramidal neurons. However, most inhibitory synapses in the neocortex are formed onto pyramidal cell dendrites, where theoretical studies suggest they may focally regulate cellular activity. The precision of GABAergic control over dendritic electrical and biochemical signaling is unknown. By using cell type-specific optical stimulation in combination with two-photon calcium (Ca2+) imaging, we show that somatostatin-expressing interneurons exert compartmentalized control over postsynaptic Ca2+ signals within individual dendritic spines. This highly focal inhibitory action is mediated by a subset of GABAergic synapses that directly target spine heads. GABAergic inhibition thus participates in localized control of dendritic electrical and biochemical signaling.

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