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. Author manuscript; available in PMC: 2012 Feb 1.
Published in final edited form as: Can J Anaesth. 2011 Jan 7;58(2):191–205. doi: 10.1007/s12630-010-9419-9

Figure 7.

Figure 7

The scheme depicts equilibrium two-state allosteric co-agonism for GABA and etomidate actions on GABAA receptors, as described by Rüsch et al (15). There are two equivalent GABA sites and two equivalent etomidate sites. Only doubly-bound states are shown, both for simplicity and because they are the most highly populated states when ligands are present. GABA binding transitions are blue, etomidate binding transitions are red, and gating (opening and closing) transitions are black. The L0 parameter describes the basal equilibrium between closed (R) and open (O) states. KG is the dissociation constant for GABA interactions with R-state receptors and KG* is the dissociation constant for GABA interactions with O-state receptors. The GABA efficacy factor, c, is defined as KG*/KG. KE is the dissociation constant for etomidate interactions with R-state receptors and KE* is the dissociation constant for etomidate interactions with O-state receptors. The anesthetic efficacy factor, d, is defined as KE*/KE.