title: Cell type-specific GABA A receptor-mediated tonic inhibition in mouse neocortex.
abstract: Activity of extrasynaptic GABA A receptors mediating tonic inhibition is thought to play an important role for the excitability of the mammalian cerebral cortex. However, little is known about the cell type-specific expression of tonic inhibition in particular types of cortical interneurons. Here, we used transgenic mice expressing green fluorescent protein (GFP) in somatostatin-positive (SOM) interneurons and investigated tonic inhibition in SOM interneurons versus pyramidal cells in neocortical layers 2/3. In brain slices, pyramidal cells showed a tonic current of 66 +/- 19 pA in response to the delta-subunit selective GABA A agonist THIP (1 microM). On the other hand, tonic inhibition was absent in SOM interneurons (8 +/- 1 pA) in response to THIP. As opposed to pyramidal cells, SOM interneurons were also insensitive to the delta-subunit preferring neurosteroid allotetrahydrodeoxycorticosterone (THDOC) (100 nM) and to elevated endogenous GABA levels in the slice. Finally, SOM interneurons received only 45% of the phasic charge transfer during GABA A receptor-mediated synaptic activity compared with pyramidal cells. Altogether, our study indicates that SOM interneurons receive relatively weak inhibitory input and cannot be brought under the influence of tonic inhibition.
authors.affiliation: Synaptic Physiology Laboratory, Institute of Physiology and Biophysics, University of Aarhus, Aarhus, Denmark.
authors.forename: Irina
authors.initials: I
authors.lastname: Vardya
authors.forename: Kim R
authors.initials: KR
authors.lastname: Drasbek
authors.forename: Zita
authors.initials: Z
authors.lastname: Dósa
authors.forename: Kimmo
authors.initials: K
authors.lastname: Jensen
mesh_terms: D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D004347:Drug Interactions; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D007555:Isoxazoles / Q000494:pharmacology; D051379:Mice; D019579:Neocortex / Q000166:cytology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000145:classification* / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011930:Reaction Time / Q000187:drug effects; D011963:Receptors, GABA-A / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D000777:Anesthetics; D018755:GABA Agonists; D018756:GABA Antagonists; D007555:Isoxazoles; D011963:Receptors, GABA-A; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D005680:gamma-Aminobutyric Acid; C015542:gaboxadol