The interaction of anaesthetic steroids with recombinant glycine and GABAA receptors

C. J. Weir; A. T. Y. Ling; D. Belelli; J. A.W. Wildsmith; J. A. Peters; J. J. Lambert

doi:10.1093/bja/aeh125

The interaction of anaesthetic steroids with recombinant glycine and GABA_A receptors

C. J. Weir, A. T. Y. Ling, D. Belelli, J. A.W. Wildsmith, J. A. Peters, J. J. Lambert

DArcy Thompson Unit

Research output: Contribution to journal › Article › peer-review

77 Citations (Scopus)

Abstract

Background. Anaesthetic steroids are established positive allosteric modulators of GABA_A receptors, but little is known concerning steroid modulation of strychnine-sensitive glycine receptors, the principal mediators of fast, inhibitory neurotransmission in the brain stem and spinal cord. This study compared the modulatory actions of five anaesthetic pregnane steroids and two non-anaesthetic isomers at human recombinant α₁ glycine and α ₁β₂γ_2L GABA_A receptors. Methods. Recombinant α₁ glycine or α₁β₂γ_2L GABA_A receptors were expressed in Xenopus laevis oocytes and agonist-evoked currents recorded under voltage-clamp. Steroid modulation of currents evoked by GABA, or glycine, was quantified by determining the potency (EC₅₀) and maximal effect of the compounds. Results. The anaesthetics minaxolone (EC₅₀ = 1.3 μM), Org20599 (EC₅₀ = 1.1 μM) and alphaxalone (EC₅₀=2.2 μM) enhanced currents mediated by GABA_A receptors. The anaesthetics also enhanced currents mediated by glycine receptors, although with higher EC₅₀ values (minaxolone 13.1 μM; Org20599=22.9 μM and alphaxalone=27.8 μM). The maximal enhancement (to 780-950% of control) produced by the three steroids acting at the GABA_A receptor was similar, but currents evoked by glycine were potentiated with increasing effectiveness by alphaxalone (199%) <Org20599 (525%) <minaxolone (1197%). The anaesthetic isomers, 5α-pregnan-3α-ol-20-one and 5β-pregnan-3α-ol-20-one (eltanolone) enhanced GABA_A receptor-mediated currents with similar potency and efficacy, but only the former enhanced glycine, the latter causing inhibition. The non-anaesthetic steroids 5α-pregnan-3β-ol-20-one and 5β-pregnan-3β-ol-20-one modulated neither GABA_A, nor glycine, receptors. Conclusions. The data demonstrate that structure-activity relationships for steroid modulation at glycine and GABA_A receptors differ. Comparing the EC₅₀ values reported here with free plasma concentrations during steroid-induced anaesthesia indicates that a selective modulation of GABA_A receptor activity is likely to occur in vivo.

Original language	English
Pages (from-to)	704-711
Number of pages	8
Journal	British journal of anaesthesia
Volume	92
Issue number	5
DOIs	https://doi.org/10.1093/bja/aeh125
Publication status	Published - May 2004

Keywords

Anaesthetics i.v., steroid, minaxolone
GABA receptors
Glycine receptors

ASJC Scopus subject areas

Anesthesiology and Pain Medicine

Access to Document

10.1093/bja/aeh125

Cite this

@article{7b1faf2503c7407c8f0a2f88cbd6c5f0,

title = "The interaction of anaesthetic steroids with recombinant glycine and GABAA receptors",

abstract = "Background. Anaesthetic steroids are established positive allosteric modulators of GABAA receptors, but little is known concerning steroid modulation of strychnine-sensitive glycine receptors, the principal mediators of fast, inhibitory neurotransmission in the brain stem and spinal cord. This study compared the modulatory actions of five anaesthetic pregnane steroids and two non-anaesthetic isomers at human recombinant α1 glycine and α 1β2γ2L GABAA receptors. Methods. Recombinant α1 glycine or α1β2γ2L GABAA receptors were expressed in Xenopus laevis oocytes and agonist-evoked currents recorded under voltage-clamp. Steroid modulation of currents evoked by GABA, or glycine, was quantified by determining the potency (EC50) and maximal effect of the compounds. Results. The anaesthetics minaxolone (EC50 = 1.3 μM), Org20599 (EC50 = 1.1 μM) and alphaxalone (EC50=2.2 μM) enhanced currents mediated by GABAA receptors. The anaesthetics also enhanced currents mediated by glycine receptors, although with higher EC50 values (minaxolone 13.1 μM; Org20599=22.9 μM and alphaxalone=27.8 μM). The maximal enhancement (to 780-950% of control) produced by the three steroids acting at the GABAA receptor was similar, but currents evoked by glycine were potentiated with increasing effectiveness by alphaxalone (199%) A receptor-mediated currents with similar potency and efficacy, but only the former enhanced glycine, the latter causing inhibition. The non-anaesthetic steroids 5α-pregnan-3β-ol-20-one and 5β-pregnan-3β-ol-20-one modulated neither GABAA, nor glycine, receptors. Conclusions. The data demonstrate that structure-activity relationships for steroid modulation at glycine and GABAA receptors differ. Comparing the EC50 values reported here with free plasma concentrations during steroid-induced anaesthesia indicates that a selective modulation of GABAA receptor activity is likely to occur in vivo.",

keywords = "Anaesthetics i.v., steroid, minaxolone, GABA receptors, Glycine receptors",

author = "Weir, {C. J.} and Ling, {A. T. Y.} and D. Belelli and Wildsmith, {J. A.W.} and Peters, {J. A.} and Lambert, {J. J.}",

year = "2004",

month = may,

doi = "10.1093/bja/aeh125",

language = "English",

volume = "92",

pages = "704--711",

journal = "British journal of anaesthesia",

issn = "0007-0912",

publisher = "Elsevier",

number = "5",

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T1 - The interaction of anaesthetic steroids with recombinant glycine and GABAA receptors

AU - Weir, C. J.

AU - Ling, A. T. Y.

AU - Belelli, D.

AU - Wildsmith, J. A.W.

AU - Peters, J. A.

AU - Lambert, J. J.

PY - 2004/5

Y1 - 2004/5

N2 - Background. Anaesthetic steroids are established positive allosteric modulators of GABAA receptors, but little is known concerning steroid modulation of strychnine-sensitive glycine receptors, the principal mediators of fast, inhibitory neurotransmission in the brain stem and spinal cord. This study compared the modulatory actions of five anaesthetic pregnane steroids and two non-anaesthetic isomers at human recombinant α1 glycine and α 1β2γ2L GABAA receptors. Methods. Recombinant α1 glycine or α1β2γ2L GABAA receptors were expressed in Xenopus laevis oocytes and agonist-evoked currents recorded under voltage-clamp. Steroid modulation of currents evoked by GABA, or glycine, was quantified by determining the potency (EC50) and maximal effect of the compounds. Results. The anaesthetics minaxolone (EC50 = 1.3 μM), Org20599 (EC50 = 1.1 μM) and alphaxalone (EC50=2.2 μM) enhanced currents mediated by GABAA receptors. The anaesthetics also enhanced currents mediated by glycine receptors, although with higher EC50 values (minaxolone 13.1 μM; Org20599=22.9 μM and alphaxalone=27.8 μM). The maximal enhancement (to 780-950% of control) produced by the three steroids acting at the GABAA receptor was similar, but currents evoked by glycine were potentiated with increasing effectiveness by alphaxalone (199%) A receptor-mediated currents with similar potency and efficacy, but only the former enhanced glycine, the latter causing inhibition. The non-anaesthetic steroids 5α-pregnan-3β-ol-20-one and 5β-pregnan-3β-ol-20-one modulated neither GABAA, nor glycine, receptors. Conclusions. The data demonstrate that structure-activity relationships for steroid modulation at glycine and GABAA receptors differ. Comparing the EC50 values reported here with free plasma concentrations during steroid-induced anaesthesia indicates that a selective modulation of GABAA receptor activity is likely to occur in vivo.

AB - Background. Anaesthetic steroids are established positive allosteric modulators of GABAA receptors, but little is known concerning steroid modulation of strychnine-sensitive glycine receptors, the principal mediators of fast, inhibitory neurotransmission in the brain stem and spinal cord. This study compared the modulatory actions of five anaesthetic pregnane steroids and two non-anaesthetic isomers at human recombinant α1 glycine and α 1β2γ2L GABAA receptors. Methods. Recombinant α1 glycine or α1β2γ2L GABAA receptors were expressed in Xenopus laevis oocytes and agonist-evoked currents recorded under voltage-clamp. Steroid modulation of currents evoked by GABA, or glycine, was quantified by determining the potency (EC50) and maximal effect of the compounds. Results. The anaesthetics minaxolone (EC50 = 1.3 μM), Org20599 (EC50 = 1.1 μM) and alphaxalone (EC50=2.2 μM) enhanced currents mediated by GABAA receptors. The anaesthetics also enhanced currents mediated by glycine receptors, although with higher EC50 values (minaxolone 13.1 μM; Org20599=22.9 μM and alphaxalone=27.8 μM). The maximal enhancement (to 780-950% of control) produced by the three steroids acting at the GABAA receptor was similar, but currents evoked by glycine were potentiated with increasing effectiveness by alphaxalone (199%) A receptor-mediated currents with similar potency and efficacy, but only the former enhanced glycine, the latter causing inhibition. The non-anaesthetic steroids 5α-pregnan-3β-ol-20-one and 5β-pregnan-3β-ol-20-one modulated neither GABAA, nor glycine, receptors. Conclusions. The data demonstrate that structure-activity relationships for steroid modulation at glycine and GABAA receptors differ. Comparing the EC50 values reported here with free plasma concentrations during steroid-induced anaesthesia indicates that a selective modulation of GABAA receptor activity is likely to occur in vivo.

KW - Anaesthetics i.v., steroid, minaxolone

KW - GABA receptors

KW - Glycine receptors

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