The Journal of General Physiology
VISIT JCB ONLINE!
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
Published online January 28, 2008
doi:10.1085/jgp.200709871
The Journal of General Physiology, Vol. 131, No. 2, 163-181
The Rockefeller University Press, 0022-1295 $30.00
© 2008 Keramidas et al.
This Article
Right arrow Full Text
Right arrow PDF (Full Text)
Right arrow PPT slides of all figures
Right arrow Supplemental Material Index
Right arrow Alert me when this article is cited
Right arrow Citation Map
Services
Right arrow Email this article
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new content in the JGP
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Keramidas, A.
Right arrow Articles by Harrison, N. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Keramidas, A.
Right arrow Articles by Harrison, N. L.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

ARTICLE

 Agonist-dependent Single Channel Current and Gating in {alpha}4β2{delta} and {alpha}1β2{gamma}2S GABAA Receptors



Angelo Keramidas and Neil L. Harrison

CV Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021

Correspondence to Angelo Keramidas: ank2013{at}cornell.med.edu

The family of {gamma}-aminobutyric acid type A receptors (GABAARs) mediates two types of inhibition in the mammalian brain. Phasic inhibition is mediated by synaptic GABAARs that are mainly comprised of {alpha}1, β2, and {gamma}2 subunits, whereas tonic inhibition is mediated by extrasynaptic GABAARs comprised of {alpha}4/6, β2, and {delta} subunits. We investigated the activation properties of recombinant {alpha}4β2{delta} and {alpha}1β2{gamma}2S GABAARs in response to GABA and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3(2H)-one (THIP) using electrophysiological recordings from outside-out membrane patches. Rapid agonist application experiments indicated that THIP produced faster opening rates at {alpha}4β2{delta} GABAARs (β ~1600 s–1) than at {alpha}1β2{gamma}2S GABAARs (β ~ 460 s–1), whereas GABA activated {alpha}1β2{gamma}2S GABAARs more rapidly (β ~1800 s–1) than {alpha}4β2{delta} GABAARs (β < 440 s–1). Single channel recordings of {alpha}1β2{gamma}2S and {alpha}4β2{delta} GABAARs showed that both channels open to a main conductance state of ~25 pS at –70 mV when activated by GABA and low concentrations of THIP, whereas saturating concentrations of THIP elicited ~36 pS openings at both channels. Saturating concentrations of GABA elicited brief (<10 ms) openings with low intraburst open probability (PO ~ 0.3) at {alpha}4β2{delta} GABAARs and at least two "modes" of single channel bursting activity, lasting ~100 ms at {alpha}1β2{gamma}2S GABAARs. The most prevalent bursting mode had a PO of ~0.7 and was described by a reaction scheme with three open and three shut states, whereas the "high" PO mode (~0.9) was characterized by two shut and three open states. Single channel activity elicited by THIP in {alpha}4β2{delta} and {alpha}1β2{gamma}2S GABAARs occurred as a single population of bursts (PO ~0.4–0.5) of moderate duration (~33 ms) that could be described by schemes containing two shut and two open states for both GABAARs. Our data identify kinetic properties that are receptor-subtype specific and others that are agonist specific, including unitary conductance.

Abbreviations used in this paper: GABAAR, {gamma}-aminobutyric acid type A receptor; LGIC, ligand-gated ion channel; RI, rectification index; THIP, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3(2H)-one.


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?




  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents