The Role of Neuronal Leak Channels in Anesthesia

<p>Volatile anesthetics (VAs) cause profound effects, including reversible lossof consciousness and immobility. The mechanism of action of VAs remains oneof the great, unsolved puzzles of neuroscience and medicine. Recent geneticstudies revealed that mutations that change anesthetic sensitivity in modelorganisms alter specific sodium (NCA or NALCN) and potassium (K2P) leakchannels that establish the neuronal resting membrane potential (RMP). Usingthe nematode, C. elegans, I tested the effect on anesthetic sensitivity ofcombining these potassium and sodium leak channel mutations in a singleanimal. I also used the light activated proteins, channelrhodopsin-2 andhalorhodopsin, to modulate the neuronal RMP in a wild type background anddetermined the effects of changing the RMP on anesthetic sensitivity.</p><p>In C. elegans, loss of a hyperpolarizing potassium leak through the K2Pchannels caused a resistance to halothane, a VA. Interestingly, gain of functionmutations in this channel or associated proteins displayed a hypersensitivity tohalothane. Combining the hyperpolarizing NCA loss of function mutation with again of function K2P mutation in a single animal caused a 17-fold increase insensitivity to halothane compared to wild type. These results suggested thathalothane might function by hyperpolarizing neuronal RMP.Halothane induced immobility is also acutely and completely reversed bychannelrhodopsin-2 based depolarization of the cholinergic neurons.Furthermore, hyperpolarizing cholinergic neurons via halorhodopsin activationincreases sensitivity to halothane. Immobility induced by isoflurane, a structurallysimilar anesthetic, is not affected by optogenetic manipulation of RMP, therebyexcluding the possibility of non-specific hyperactivity caused bychannelrhodopsin-2 activation.</p><p>These results indicate that the effects on the neuronal RMP directlyunderlie the mechanism of action of halothane. The sensitivity of C. elegans tohalothane can be altered by 25-fold through genetic or optogenetic manipulationof the RMP. The ability to reverse halothane induced immobility bydepolarization of cholinergic neurons suggests that one of the majorphysiological process that halothane perturbs to cause immobility is the neuronalRMP of cholinergic neurons. Optogenetic analysis can now be used todetermine the critical sites of anesthetic action in the mammalian central nervoussystem and provide insight into complex neuronal processes, like consciousness.</p>

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Genetics

Grantor dc:publisher

Case Western Reserve University School of Graduate Studies

Year dc:date

2012

Author dc:creator

• Singaram, Vinod Krishnan

Contributors dc:contributor

• Morgan, Philip
• Sedensky, Margaret
• Salz, Helen

• Genetics
• Neurobiology
• Neurosciences
• anesthetics
• halothane
• optogenetics
• leak channels
• reversal of anesthesia
• isoflurane
• anesthesia
• channlrhodopsin
• halorhodopsin
• NCA channels
• NALCN
• two-P domain channels, K2P

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=case1339372305

OAI identifier oai:identifier

oai:etd.ohiolink.edu:case1339372305