• Vesna Tesic, Srdjan M Joksimovic, Nidia Quillinan, Kathiresan Krishnan, Douglas F Covey, Slobodan M Todorovic, and Vesna Jevtovic-Todorovic.
• Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
• Br J Anaesth. 2020 May 1; 124 (5): 603-613.

BackgroundThe most currently used general anaesthetics are potent potentiators of γ-aminobutyric acid A (GABAA) receptors and are invariably neurotoxic during the early stages of brain development in preclinical animal models. As causality between GABAA potentiation and anaesthetic-induced developmental neurotoxicity has not been established, the question remains whether GABAergic activity is crucial for promoting/enhancing neurotoxicity. Using the neurosteroid analogue, (3α,5α)-3-hydroxy-13,24-cyclo-18,21-dinorchol-22-en-24-ol (CDNC24), which potentiates recombinant GABAA receptors, we examined whether this potentiation is the driving force in inducing neurotoxicity during development.MethodsThe neurotoxic potential of CDNC24 was examined vis-à-vis propofol (2,6-diisopropylphenol) and alphaxalone (5α-pregnan-3α-ol-11,20-dione) at the peak of rat synaptogenesis. In addition to the morphological neurotoxicity studies of the subiculum and medial prefrontal cortex (mPFC), we assessed the extra-, pre-, and postsynaptic effects of these agents on GABAergic neurotransmission in acute subicular slices from rat pups.ResultsCDNC24, like alphaxalone and propofol, caused dose-dependent hypnosis in vivo, with a higher therapeutic index. CDNC24 and alphaxalone, unlike propofol, did not cause developmental neuroapoptosis in the subiculum and mPFC. Propofol potentiated post- and extrasynaptic GABAA currents as evidenced by increased spontaneous inhibitory postsynaptic current (sIPSC) decay time and prominent tonic currents, respectively. CDNC24 and alphaxalone had a similar postsynaptic effect, but also displayed a strong presynaptic effect as evidenced by decreased frequency of sIPSCs and induced moderate tonic currents.ConclusionsThe lack of neurotoxicity of CDNC24 and alphaxalone may be at least partly related to suppression of presynaptic GABA release in the developing brain.Copyright © 2020 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

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