2019 Fiscal Year Research-status Report
Direct Optogenetic Investigation of Cortical Excitability and Connectivity in Slow Wave Sleep
| Project/Area Number |
18K06849
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| Research Institution | University of Tsukuba |
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Principal Investigator |
Vogt Kaspar 筑波大学, 国際統合睡眠医科学研究機構, 准教授 (80740034)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | sleep / cortex / response / LFP / single unit / spike / Channelrhodopsin |
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| Outline of Annual Research Achievements |
Optogenetic stimulation of thalamocortical afferents to the cortex results in an excitatory response followed by an inhibitory pause. This can be observed both in the local field potential and in the number of action potentials generated. Surprisingly, this biphasic response is much larger in non-rapid eye movement (NREM) sleep than when the animal is awake. Responses during rapid eye movement (REM) sleep are between waking and NREM, but closer to waking.
The time for the response to change between waking and NREM is 1-2 minutes, much faster than homeostatic plasticity processes, but compatible with neuromodulatory changes that we know occur in these transitions. Waking and REM sleep are characterized by high cholinergic tone, whereas NREM sleep is characterized by very low cholinergic activity. We therefore hypothesize that changes in cholinergic tone modulate the cortical response.
Interestingly, large responses also had a longer excitatory phase. This matches results from other researchers, who found this phenomenon when they decreased feedforward inhibition experimentally. We therefore hypothesize that the reduced cholinergic activity in the cortex during NREM sleep results in a loss of feedforward inhibition and contributes to the increased responses.
These results were presented at international conferences and published in the journal Scientific Reports.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
We were able to successfully complete our first set of recordings, analyze the data and publish the results.
We have now started to implement an in-vitro strategy to test some of the neuropharmacological hypotheses that we developed from our findings.
We wanted to test more pathways and so far have not been able to record many animals.
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| Strategy for Future Research Activity |
We will attempt to perform more in-vivo recordings on other cortical pathways to test, whether the increased responses in sleep are universally found in the brain, or only for specific pathways.
We have started in-vitro experiments to test the hypothesis that cholinergic modulation causes the increased response of the cortex during sleep.
We will use adeno-associated viruses to transfect cortical pathways with channelrhodopsin. Later, acute brain slices will be obtained and cortical neurons will be patched in-vitro and their reaction to optogenetic activation of the labelled pathways will be recorded. We will then use pharmacological tools to investigate the role of the cholinergic system in controlling these responses. Cholinergic agonists will mimic waking and cholinergic antagonists will mimic the NREM state.
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| Causes of Carryover |
Travel expenses were lower than expected due to the Covid-19 situation. Experiments also progressed a bit more slowly due to this fact. Some consumables and miscellaneous costs were therefore not incurred.
We are planning to finish in-vivo recordings of ChR2 expressing mice (ongoing) and we are setting up in-vitro recordings in acute brain slice preparations.
Both will require purchase of mice and consumables for molecular biology (virus generation) and for pharmacological agents.
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Research Products
(3 results)
