Isoflurane Suppresses the Excitability and Synaptic Transmission of Spinal Nociceptive Pathway in Rats

Abstract

Background: Isoflurane (IFL), one of the most widely used volatile anesthetics, has an anti-nociceptive effect at the spinal cord level. However, the reported spinal mechanisms of IFL analgesic action remain controversial. The aim of this study was to examine the effect of IFL on the excitability of spinal substantia gelatinosa (SG, lamina II) neurons and the synaptic transmission from primary nociceptive fibers to SG neurons.Methods: Parasagittal spinal slices with a dorsal root attached were cut from the Sprague-Dawley rats (4-6 weeks old). Whole-cell patch-clamp recordings were made from SG neurons at room temperature. Dorsal root stimulation was used to evoke excitatory postsynaptic currents (eEPSCs). Depolarizing current injection was used to display the firing pattern of action potentials. IFL was given as volume percent (3%) by passing the gas mixture (flow rate, 0.5 L/minute) into equilibrated artificial cerebral spinal fluid (ACSF) for at least 15 minutes at room temperature.Results: IFL significantly suppressed the peak amplitude of monosynaptic eEPSCs mediated by primary Aδ and C fibers. Regardless of neuron types, IFL significantly decreased the frequency of action potentials in all SG neurons tested.Conclusions: IFL may play analgesic role through inhibiting or weakening the excitability and synaptic transmission of spinal nociceptive pathway. Citation: Jie Liu, Gen-Lin Ji, Jian-Min Li, Tun Liu, Qun Wang, Ya-Nan Pu, et al. Isoflurane suppresses the excitability and synaptic transmission of spinal nociceptive pathway in rats. J Anesth Perioper Med 2015; 2: 61-5. doi: 10.24015/JAPM.2015.0010This is an open-access article, published by Evidence Based Communications (EBC). This work is licensed under the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium or format for any lawful purpose. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.