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Inhibition of a tonic inhibitory conductance in mouse hippocampal neurones by negative allosteric modulators of α5 subunit-containing γ-aminobutyric acid type A receptors: implications for treating cognitive deficits

Manzo, Marc A., Wang, Dian-Shi, Li, Winston W., Pinguelo, Arsène, Popa, Mariana O., Khodaei, Shahin, Atack, John R., Ross, Ruth A. and Orser, Beverley A. 2021. Inhibition of a tonic inhibitory conductance in mouse hippocampal neurones by negative allosteric modulators of α5 subunit-containing γ-aminobutyric acid type A receptors: implications for treating cognitive deficits. British Journal of Anaesthesia 126 (3) , pp. 674-683. 10.1016/j.bja.2020.11.032
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Abstract

Background Multiple cognitive and psychiatric disorders are associated with an increased tonic inhibitory conductance that is generated by α5 subunit-containing γ-aminobutyric acid type A (α5 GABAA) receptors. Negative allosteric modulators that inhibit α5 GABAA receptors (α5-NAMs) are being developed as treatments for these disorders. The effects of α5-NAMs have been studied on recombinant GABAA receptors expressed in non-neuronal cells; however, no study has compared drug effects on the tonic conductance generated by native GABAA receptors in neurones, which was the goal of this study. Methods The effects of five α5-NAMs (basmisanil, Ono-160, L-655,708, α5IA, and MRK-016) on tonic current evoked by a low concentration of GABA were studied using whole-cell recordings in cultured mouse hippocampal neurones. Drug effects on current evoked by a saturating concentration of GABA and on miniature inhibitory postsynaptic currents (mIPSCs) were also examined. Results The α5-NAMs caused a concentration-dependent decrease in tonic current. The potencies varied as the inhibitory concentration for 50% inhibition (IC50) of basmisanil (127 nM) was significantly higher than those of the other compounds (0.4–0.8 nM). In contrast, the maximal efficacies of the drugs were similar (35.5–51.3% inhibition). The α5-NAMs did not modify current evoked by a saturating GABA concentration or mIPSCs. Conclusions Basmisanil was markedly less potent than the other α5-NAMs, an unexpected result based on studies of recombinant α5 GABAA receptors. Studying the effects of α5 GABAA receptor-selective drugs on the tonic inhibitory current in neurones could inform the selection of compounds for future clinical trials.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Publisher: Elsevier
ISSN: 0007-0912
Date of First Compliant Deposit: 15 March 2021
Date of Acceptance: 16 November 2020
Last Modified: 16 Mar 2021 10:30
URI: http://orca.cardiff.ac.uk/id/eprint/139790

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