• V S Eckle, U Rudolph, B Antkowiak, and C Grasshoff.
• Experimental Anaesthesiology Section, Department of Anaesthesiology and Intensive Care, Eberhard-Karls-University, Tübingen, Germany veit-simon.eckle@uni-tuebingen.de.
• Br J Anaesth. 2015 Mar 1;114(3):491-8.

BackgroundSurgical interventions like skin incisions trigger withdrawal reflexes which require motor neurones and local circuit interneurones in the spinal ventral horn. This region plays a key role in mediating immobilizing properties of the GABAergic anaesthetic propofol. However, it is unclear how propofol modulates GABA(A) receptors in the spinal ventral horn and whether tonic or phasic inhibition is involved.MethodsOrganotypic spinal cord tissue slices were prepared from mice. Whole-cell recordings were performed for quantifying effects of propofol on GABA(A) receptor-mediated phasic transmission and tonic conductance.ResultsPropofol increased GABAergic phasic transmission by a prolongation of the decay time constant in a concentration-dependent manner. The amount of the charge transferred per inhibitory post-synaptic current, described by the area under the curve, was significantly augmented by 1 µM propofol (P<0.01). A GABA(A) receptor-mediated tonic current was not induced by 1 µM propofol but at a concentration of 5 µM (P<0.05).ConclusionsPropofol depresses ventral horn interneurones predominantly by phasic rather than by tonic GABA(A) receptor-mediated inhibition. However, the present results suggest that the involvement of a tonic inhibition might contribute to the efficacy of propofol to depress nociceptive reflexes at high concentrations of the anaesthetic.© The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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