Effects of general anesthetics on molecular dynamics and conformation of neuronal receptor channel protains - Molecular mechanism of general anesthesia -

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1)Effects of inhalational anesthetics on recombinant GABA_A receptors and NMDA receptors expressed in Xenopus oocyte : Different combinations of GABA_A receptor subunits (α1β2 and α1β2γ2s) and NMDA receptor (ζ1ε1) were injected to Xenopus oocyte followed by incubation at 20℃ for >48h. The electrophystological recordings were made by using the two electrode-voltage champ technique. Volatile anesthetics potentiated GABA-induced current in dose dependent manners in the α1β2 and α1β2γ2s receptors, but xenon (Xe), nitrous oxide (N_2O) showed no significant potentiation. On the contrary, volatile anesthetics did not affect NMDA-induced current in the ζ1ε1 receptor, Xe and N_2O depressed it dose-dependently.2)Effects of Xe and N_2O on the human neuronal (α_7)_5 nAch receptor expressed in Xenopus oocyte : At clinically relevant concentrations, Xe and N_2O reversibly inhibited the ACh-induced currents of the (α_7)_5 nAch receptor in a concentration-dependent manner. The inhibitory actions of both anesthetics at the (α_7)_5 nAch were non-competitive and voltage-independent.3)Effects of inhalational anesthetics on human-cloned 5-HT_3 receptor expressed in Xenopus oocyte : Inhalational anesthetics produced deverse effects on the 5-HT_3 receptor. Both halothane and isoflurane enhanced 5-HT_3 receptor function in a concentration-dependent manner. Sevoflurane inhibited the 5-HT-induced current noncopmetitively, whereas Xe and N_2O inhibited the 5-HT_3 receptor competitively. The results suggest that inhalational anesthetics acts on neuronal receptors in the specific manner.