Isoflurane prevents transitions to tonic and burst firing modes in thalamic neurons.
We used patch-clamp whole-cell techniques to assess the effects of a volatile anaesthetic on thalamic firing modes in rat brain slices. Isoflurane application in clinical concentrations (0.5-2%) reversibly prevented voltage-dependent transitions to repetitive spike and burst firing modes in ventrobasal neurons. In voltage-clamp studies, isoflurane increased leak conductance, which shunted tonic and burst firing. Isoflurane also blocked the low-threshold Ca(2+)-current underlying the burst mode of firing, by increasing leak current and depressing membrane Ca(2+)-channel activity. We suggest that the mechanism of anaesthesia is distinct from sleep, although both states critically involve excitabilities of thalamic neurons.
Ries
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CR
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
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D000818:Animals; D001143:Arousal / Q000187:drug effects; D004594:Electrophysiology; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D013788:Thalamus / Q000166:cytology / Q000187:drug effects*
D013779:Tetrodotoxin; D007530:Isoflurane