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Br J Anaesth. 2005 Jun;94(6):784-90. Epub 2005 Mar 18.

Effects of isoflurane and xenon on Ba2+-currents mediated by N-type calcium channels.

Author information

1
Department of Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College London, Chelsea and Westminster Campus, 369 Fulham Road, London SW10 9NH, UK.

Abstract

BACKGROUND:

Isoflurane and xenon are inhalation general anaesthetics with differing clinical profiles and contrasting synaptic actions. Both agents have been shown to depress excitatory synaptic responses. Whether this is via pre-synaptic or post-synaptic mechanisms has not been determined clearly. N-type calcium channels are a putative pre-synaptic target for these agents. We tested whether N-type calcium channels were sensitive to isoflurane and xenon and whether there was any stereoselectivity in the effect of isoflurane.

METHODS:

We used patch-clamp electrophysiology on isolated HEK293 cells stably expressing N-type calcium channels to investigate the effects of isoflurane and xenon on barium currents mediated by N-type calcium channels.

RESULTS:

Racemic isoflurane caused a concentration-dependent reduction (11-35%) in the peak current through the N-type channels in the concentration range 0.15-1.22 mM. In the clinically relevant concentration range the inhibition was small. At an isoflurane concentration of 0.31 mM (equivalent to 1 MAC), the peak N-type current was inhibited by 14 (1)%. The optical isomers of isoflurane were found to be equally potent at inhibiting currents through N-type channels. The inert gas anaesthetic xenon was found to have no measureable effect on N-type channels at a concentration of 3.4 mM (approximately 1 MAC).

CONCLUSIONS:

These results suggest that N-type calcium channels are not the targets mediating general anaesthesia with these two inhalation agents.

PMID:
15778267
DOI:
10.1093/bja/aei126
[Indexed for MEDLINE]
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