Layer- and cell-type-specific tonic GABAergic inhibition of pyramidal neurons in the rat visual cortex
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NEUROSCIENCE
Layer- and cell-type-specific tonic GABAergic inhibition of pyramidal neurons in the rat visual cortex Hyun-Jong Jang & Kwang-Hyun Cho & Myung-Jun Kim & Shin Hee Yoon & Duck-Joo Rhie
Received: 25 April 2013 / Revised: 11 June 2013 / Accepted: 12 June 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Tonic inhibition mediated by persistent activation of +-aminobutyric acidA (GABAA) receptors by ambient GABA plays a crucial role in the regulation of network excitability and neuronal signal processing. Varying degrees in the strength of tonic inhibition were detected across different cell types throughout the brain. Since sensory information flows through cortical layers in a specific order, the characteristics of tonic inhibition in different cortical layers are of interest. Therefore, we examined the properties of tonic inhibition in pyramidal neurons (PyNs) throughout the rat visual cortex. Layer 2/3 PyNs and burst-spiking PyNs in layers 5 and 6 showed prominent tonic GABAA currents. Tonic GABAA currents in layer 4 star PyNs and regular-spiking PyNs in layers 5 and 6 were much weaker. The magnitude of tonic currents correlated well with the inhibition of spike generation. The amplitude of tonic GABAA currents measured with bicuculline and gabazine, the two different GABAA receptor blockers, did not differ. The differences in the expression levels of extrasynaptic GABAA receptors might be the major contributor to the differences in tonic GABAA currents among cell types. Furthermore, α5 subunits might contribute significantly to tonic currents in infragranular burst-spiking PyNs, especially in layer 5. These results suggest that ambient GABA might exert differential effects on the neuronal integration in a layer- and cell-type-specific manner and thus
Electronic supplementary material The online version of this article (doi:10.1007/s00424-013-1313-1) contains supplementary material, which is available to authorized users. H.
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