Tonically Active Inhibition Selectively Controls Feedforward Circuits in Mouse Barrel Cortex
| Autor: | Molly M. Huntsman, Scott M. Paluszkiewicz, Peijun Li, Esther Krook-Magnuson |
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| Rok vydání: | 2008 |
| Předmět: |
Male
Patch-Clamp Techniques Physiology Action Potentials Neural Inhibition In Vitro Techniques Inhibitory postsynaptic potential Tonic (physiology) Mice Thalamus medicine Animals Patch clamp GABA Agonists Cerebral Cortex Neurons GABAA receptor Chemistry Lysine General Neuroscience Dose-Response Relationship Radiation Isoxazoles Articles Barrel cortex Receptors GABA-A Electric Stimulation Mice Inbred C57BL medicine.anatomical_structure Cerebral cortex Excitatory postsynaptic potential Female Nerve Net Neuroscience |
| Zdroj: | Journal of Neurophysiology. 100:932-944 |
| ISSN: | 1522-1598 0022-3077 |
| DOI: | 10.1152/jn.01360.2007 |
| Popis: | Tonic inhibition mediated by extrasynaptic γ-aminobutyric acid type A (GABAA) receptors is a powerful conductance that controls cell excitability. Throughout the CNS, tonic inhibition is expressed at varying degrees across different cell types. Despite a rich history of cortical interneuron diversity, little is known about tonic inhibition in the different classes of cells in the cerebral cortex. We therefore examined the cell-type specificity and functional significance of tonic inhibition in layer 4 of the mouse somatosensory barrel cortex. In situ hybridization and immunocytochemistry showed moderate δ-subunit expression across the barrel structures. Whole cell patch-clamp recordings additionally indicated that significant levels of tonic inhibition can be found across cell types, with differences in the magnitude of inhibition between cell types. To activate tonic currents, we used 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP, a superagonist at δ-subunit–containing GABAA receptors) at a concentration that did not affect synaptic decay kinetics. THIP produced greater shifts in baseline holding current in inhibitory cells (low-threshold spiking [LTS], 109 ± 17 pA; fast spiking [FS], 111 ± 15 pA) than in excitatory cells (39 ± 10 pA; P < 0.001). In addition to these differences across cell types, there was also variability within inhibitory cells. FS cells with faster action potentials had larger baseline shifts. Because FS cells are known mediators of feedforward inhibition, we tested whether THIP-induced tonic conductance selectively controls feedforward circuits. THIP application resulted in the abolishment of the inhibitory postsynaptic potential in thalamic-evoked disynaptic responses in a subset of excitatory neurons. These data suggest multiple feedforward circuits can be differentiated by the inhibitory control of the presynaptic inhibitory neuron. |
| Databáze: | OpenAIRE |
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