PT  - JOURNAL ARTICLE
AU  - Allison L. Germann
AU  - Spencer R. Pierce
AU  - Ariel B. Burbridge
AU  - Joe Henry Steinbach
AU  - Gustav Akk
TI  - Steady-State Activation and Modulation of the Concatemeric <em>α</em>1<em>β</em>2<em>γ</em>2L GABA<sub>A</sub> Receptor
AID  - 10.1124/mol.119.116913
DP  - 2019 Sep 01
TA  - Molecular Pharmacology
PG  - 320--329
VI  - 96
IP  - 3
4099  - http://molpharm.aspetjournals.org/content/96/3/320.short
4100  - http://molpharm.aspetjournals.org/content/96/3/320.full
SO  - Mol Pharmacol2019 Sep 01; 96
AB  - The two-state coagonist model has been successfully used to analyze and predict peak current responses of the γ-aminobutyric acid type A (GABAA) receptor. The goal of the present study was to provide a model-based description of GABAA receptor activity under steady-state conditions after desensitization has occurred. We describe the derivation and properties of the cyclic three-state resting-active-desensitized (RAD) model. The relationship of the model to receptor behavior was tested using concatemeric α1β2γ2 GABAA receptors expressed in Xenopus oocytes. The receptors were activated by the orthosteric agonists GABA or β-alanine, the allosteric agonist propofol, or combinations of GABA, propofol, pentobarbital, and the steroid allopregnanolone, and the observed steady-state responses were compared with those predicted by the model. A modified RAD model was employed to analyze and describe the actions on steady-state current of the inhibitory steroid pregnenolone sulfate. The findings indicate that the steady-state activity in the presence of multiple active agents that interact with distinct binding sites follows standard energetic additivity. The derived equations enable prediction of peak and steady-state activity in the presence of orthosteric and allosteric agonists, and the inhibitory steroid pregnenolone sulfate.SIGNIFICANCE STATEMENT The study describes derivation and properties of a three-state resting-active-desensitized model. The model and associated equations can be used to analyze and predict peak and steady-state activity in the presence of one or more active agents.