The Arousal Effects And Neural Circuits Of Neuropeptide S Through Paraventricular Nucleus Of The Thalamus

Neuropeptide S(NPS)is an endogenous neuromodulator composed of 20 amino acids.NPS activates Gs and Gq proteins and increase intracellular Ca²⁺and c AMP levels through its receptor(NPSR)to produce cellular excitatory effects.NPS mainly distributed in the K?lliker-Fuse(KF)nucleus and pericoerulear area(peri-LC)in mice brain,while NPSR is widely distributed in the whole brain,including the olfactory cortex,subiculum complex of hippocampal formation,amygdala,hypothalamus and paraventricular thalamus(PVT).Existing studies show that central administration of NPS can promote arousal,anxiolytic-like behavior and enhance olfactory function,however,the mechanism of NPS to promote arousal is still unclear.PVT is a newly identified important arousal regulatory nucleus,in which highly expressed of NPSR and a large number of NPS nerve fibers.Therefore,this study proposed the scientific hypothesis that"NPS-NPSR system may promote arousal by activating PVT".In this study,electroencephalogram(EEG)/electromyography(EMG)were used to analyze the effect of NPS on sleep-wake state by PVT administration in mice.Then,using immunofluorescence labeled of NPSR in PVT and analysis of EEG/EMG records after combined PVT injection of NPS and its receptor antagonist[D-Val⁵]NPS to determine whether NPS plays an arousal promoting role through its receptor in PVT neurons.Finally,virus retrograde tracing combined with fluorescence in situ hybridization(FISH)dual labeling were used to reveal the neural circuitry of NPS on arousal promoting by PVT.Results:(1)Compared with the injection of saline into the PVT nucleus,NPS(0.05-0.5 nmol)dose-dependently increased the sleep latency,increased W episode duration,and decreased NREM and REM episode number in mice;(2)Abundant NPSR immunoreactive neurons can be found in the PVT.Meanwhile,the arousal promoting effects of 0.05 nmol NPS were completely antagonized by its selective receptor antagonist[D-Val⁵]NPS at 2 nmol.(3)The dual labeling results by retrograde tracing and FISH labeled NPS precursor m RNA showed that both NPS neurons in the KF nucleus and peri-LC projected into PVT,in which 83.19%±4.08%neurons were from the KF nucleus and 16.44%±4.44%neurons were from peri-LC.Conclusion:NPS activates PVT neurons through its receptors to promote arousal,and the NPS neurons that project to PVT are mainly from the KF nucleus.