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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

Table 1.

Functional Characteristics of Wild-Type and Mutant GABAA Receptors Activated with GABA +/- Etomidate

Receptor Spontaneous Activation* GABA EC50 (μM) GABA Efficacy† Etomidate EC50 (μM) Etomidate Efficacy‡ Left-Shift Ratio (CNTL/ETO)
α1β2γ2L <0.001 26 0.9 36 0.4 20
α1M236Wβ2γ2L 0.16 2.0 0.99 12 0.97 1.7
α1β2M286Wγ2L 0.04 6.6 1.0 NA <0.001 1.1
α1β2N265Sγ2L <0.001 27 0.93 78 0.03 2.3
α1β2N265Mγ2L <0.001 32 0.84 NA <0.001 0.95
*

Spontaneous activation is estimated using picrotoxin to block constitutively active receptors in the absence of agonists. The picrotoxin-sensitive current was normalized to the maximum GABA current.

†

GABA efficacy is estimated using positive allosteric modulators (etomidate or alphaxalone) to enhance the maximum current elicited by high GABA concentrations. We assume that the combination of high GABA plus allosteric enhancer activates all receptors.

‡

Etomidate efficacy is the maximum current elicited by etomidate, normalized to the maximum current elicited with GABA.