Comparison of Spinal Anesthetic Effect between Emulsified Isoflurane and Emulsified Nonimmobilizer F6

Abstract

Background: Our previous study found that emulsified isoflurane (EI) produced subarachnoid anesthesia in dogs. The spinal effect of isoflurane might account for its immobility action. 1, 2-dichlorohexafluorocyclobutane (F6) is a nonimmobilizer that is incapable of causing immobility, it is therefore interesting to know whether there are different spinal anesthetic actions between emulsified F6 and isoflurane and their underlying mechanisms. Methods: EI and emulsified F6 were intrathecally injected into rats, and motor and sensory functions were evaluated. Sodium channel currents were recorded from spinal neurons. The effect of EI and emulsified F6 on sodium channel was examined. Results: EI produced subarachnoid anesthesia (median effective concentration [EC50] at 3.65%). Duration of actions of 8% EI was similar to 1% lidocaine. Emulsified F6 did not produce spinal anesthesia at 2% (5 folds of its predicted EC50). Meanwhile, EI inhibited sodium channel currents with median inhibitory concentration (IC50) at 0.81 ± 0.09 mmol/L and hyperpolarized voltage-dependent inactivation of sodium channel (from-57.5±2.4 to-66.3±1.8 mV, P<0.01). Emulsified F6 slightly inhibited sodium channel currents and no effect was found to the channel gating. Conclusions: Neither spinal anesthetic action nor effect to sodium channel was observed for nonimmobilizer F6, while EI inhibited spinal neurons sodium channels at clinically relevant concentrations and produced spinal anesthesia.

S1PR3 Mediates Itch and Pain via Distinct TRP Channel-Dependent Pathways

“…Within this population, we observed several subsets of itch-and pain-sensing neurons that have been described previously (Caterina et al, 2000;Jordt et al, 2004;Bautista et al, 2006;Imamachi et al, 2009;Liu et al, 2009;Wilson et al, 2011;. For example, previous studies have shown that the MrgprA3 ϩ subpopulation of TRPA1 ϩ neurons is required for many forms of non-histaminergic acute and chronic itch (Liu et al, 2009;Wilson et al, 2011;Han et al, 2013;Reddy et al, 2015;Zhu et al, 2017). In keeping with our hypothesized role for S1P in itch, 80% of chloroquine-responsive MrgprA3 ϩ neurons responded to S1P (Fig.…”