Cell type-specific GABA A receptor-mediated tonic inhibition in mouse neocortex.
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.
Vardya
Irina
I
Synaptic Physiology Laboratory, Institute of Physiology and Biophysics, University of Aarhus, Aarhus, Denmark.
Drasbek
Kim R
KR
Dósa
Zita
Z
Jensen
Kimmo
K
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
D000777:Anesthetics; D018755:GABA Agonists; D018756:GABA Antagonists; D007555:Isoxazoles; D011963:Receptors, GABA-A; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D005680:gamma-Aminobutyric Acid; C015542:gaboxadol