The Role Of Parafacial Zone GABAergic Neurons In Sevoflurane/Propofol-induced Anesthesia

Objective: The EEG of general anesthesia and slow-wave sleep are very similar;General anesthesia and slow-wave sleep share some neural circuits.Therefore,this experiment attempts to understand the mechanism of general anesthesia from the perspective of the neural circuits that regulate slow-wave sleep.The parafacial nucleus(PZ)GABAergic neurons are essential for the induction and maintenance of slow-wave sleep.Its downstream nerve nucleus—the parabrachial nucleus(PB)can promote arousal and recovery of awareness of general anesthesia.Therefore,we suspect that PZ GABAergic neurones may promote loss of awareness of general anesthesia by inhibiting PB.Therefore,this experiment used c-Fos staining,chemogenetic and optogenetic techniques to regulate PZ GABAergic neurons and PZ-PB GABAergic nerve pathways,aiming to study the changes in awareness caused by general anesthetics from the perspective of neural circuits mechanism.Methods:1.The changes in the activity of PZ GABAergic neurons were observed during general anesthesia: C57 adult male mice of SPF grade were randomly selected and divided into control group(n=4),experimental group(n=4)and awake group(n=4).The mice of the experimental group received c-Fos staining after 2.26% sevoflurane(or 8?g/g/min propofol)anesthesia for 2 hours;the mice of the control group received c-Fos staining after 1.5L/min air ventilation(or 8?L/g/min chyle fat intravenous injection)for 2 hours;The mice of the awake group were anesthetized with 2.26% sevoflurane(or 8?g/g/min propofol)for 2 hours.Then we waited 1.5 hours after the mice’s recovery from sevoflurane anesthesia.Finally,The mice of the awake group received c-Fos staining2.PZ GABAergic neurons were regulated by chemogenetic/optogenetic technology on general anesthesia: VGAT-Cre adult male mice were randomly selected and divided into chemogenetic control group(n=8),activation group(n=8),In the inhibition group(n=8),after activating or inhibiting PZ GABA neurons,the loss of consciousness time(LORR time),recovery time(RORR time)and the corresponding EEG changes(EEG)of the mice under general anesthesia were recorded.Optogenetics experiments were grouped and observed with chemogenetic experiments.3.The effect of optogenetic technology on the regulation of PZ-PB GABAergic nerve pathway on general anesthesia: VGAT-Cre adult male mice were randomly selected and divided into control group(n=8),activation group(n=8),inhibitory group(n =8).optogenetic virus were injected into the bilateral PZ,and placed optical fibers in the bilateral PB.After activating/inhibiting the PB-PZ GABAergic nerve pathway with light,we observed the LORR time,RORR time and EEG of mice under general anesthesia.Results:1.The expression of c-Fos in PZ GABAergic neurons increases during general anesthesia with sevoflurane and propofol.2.During sevoflurane and propofol anesthesia,activation of PZ GABAergic neurons of mice can shorten the LORR time,prolong RORR time,increase delta waves in EEG,and reduce beta waves.what’s more,inhibition PZ GABAergic neurons to obtain The opposite result.3.Optogenetics specifically activates or inhibits the PZ-PB GABAergic nerve pathway,which does not affect the LORR time,RORR time and EEG of mice during sevoflurane and propofol anesthesia.Conclusion:1.During sevoflurane and propofol general anesthesia,the activity of PZ GABAergic neurons increases in mice.2.PZ GABAergic neurons can promote the loss of consciousness caused by sevoflurane and propofol in mice.However,whether the PZ-PB GABAergic neural pathway is involved in the process of sevoflurane and propofol-induced changes in consciousness remains to be further studied.