The Founction And Mechanism Of The NAergic Circuit From Locus Coeruleus To Ventrolateral Preoptic Area In Regulating Sleep-Wake

Sleep is an extremely important physiological function to maintain human life,and it is essential to the organism.The normal sleep-wake cycle helps to adapt to daily life and works,and the rapid transition from sleep to wakefulness can also avoid unexpected and dangerous events.With the progress and development of society,the widespread use of electronic products and the state of high-intensity work and study have led to the somnipathy,and somnipathy have always been a topic of high concern in the society.Somnipathy is the manifestation of abnormal sleep quantity and abnormal behavior during sleep,as well as the alternating disorder of normal rhythm between sleep and arousal.The maintenance and transition of sleep-wake is regulated by the central nervous system.Decoding the neural network of sleep-wake regulation is particularly important for the treatment of somnipathy and the improvement of sleep quality.For many years,studies have shown that the nuclei of monoaminergic cells in the brainstem play an important role in promoting arousal,including the locus ceruleus(LC)where noradrenergic(NAergic)neurons are concentrated.According to the classical'flip-flop switch'model,it is believed that the arousal-promoting monoaminergic cells send inhibitory outputs to the sleep-related brain area of the hypothalamus,especially the center of sleep regulation-ventrolateral preoptic area(VLPO),thus promoting arousal.However,the specific regulatory role of this pathway has not been confirmed,and the specific types of neurons involved and the regulatory mechanism are unclear.In this study,cortical electroencephalograph(EEG)recording was used to detect different sleep states of mice;cortical EEG combined with optrode recording was used to detect the activity of various types of neurons in different sleep states;virus tracer technique was used to determine the anatomical projection between different nuclei;optogenetic and chemogenetic methods were used to activate or inhibit specific types of neurons in different brain regions so as to observe the effects on sleep-wake behavior.The types of receptors acting on different neurons were recorded and detected by in vitro patch clamp,so as to reveal the mechanism of sleep-wake regulation.Studies have shown that the activity of NAergic neurons in the LC was increased during wakefulness and decreased during sleep(non-rapid eye movement(NREM)sleep and rapid eye movement(REM)sleep),inhibition of LC-NA neurons can promote sleep.And LC-NA neurons have extensive downstream and project directly to VLPO.Activation of the circuit of NAergic^LC-VLPOpromoted the transition from sleep to arousal and maintained arousal,but inhibiting this pathway did not reduce arousal or induce sleep.Optrode recording in the VLPO showed that the NAergic pathway of LC-VLPO that activated could record three different response neurons in the VLPO.one group was excited neurons,which were mainly increased during wakefulness,known as wake-active neurons;another group of inhibited neurons increased firing during sleep,it was considered to be sleep-active neurons;and a small number of neurons did not have a significant response.Through in vitro patch clamp combined with optogenetic recordings,it was found that neurons with low-threshold spik(LTS)characteristics in the VLPO could be inhibited by LC-NA neurons,while most of neurons without low-threshold spik(non-LTS)characteristics could be excited by LC-NA neurons.In addition,different types of adrenoceptor antagonists were perfused into VLPO involved brain slices.It was found that the inhibitory effect by NA on LTS neurons in the VLPO was mediated by?₂receptors,while the excitatory effect on non-LTS neurons was mediated by?₁and?receptors.In summary,our results demonstrate that the NAergic pathway of LC-VLPO plays an important role in arousal promotion,and the synergistic effect is produced by inhibition of sleep-active neurons of VLPO through?₂-receptors and activation of wake-active neurons of VLPO through?₁-receptors and?-receptors.