| Sleep deprivation (SD) caused by the state of continuing work can interfere with people's cognitive function and work capacity. And it has been considered as an important problem by modern preventive medicine and a lot of industries (such as aviation, marine, rescue, transportation, medical care, etc.). Multiple studies have been demonstrated that SD damaged cognitive function, resulting in learning and memory disability, unresponsive, distraction, disorientation, hallucinations, etc. However, the mechanisms by which SD impairs cognitive function are not clear. As a brain specific protein, Ng is involved in learning and memory process, and plays as central role in signal transduction and synaptic plasticity of the main aspects of regulation. In this study, we have observed the changes of Ng in the process of impairing cognitive function by SD and determined weather Ng exerts important functions in the signal transduction pathway.This study conducted in rats after 24h, 48h and 72h SD. Open field test (OFT) was used to observe the changes of nervous behavior of the rats before and after SD. Electrophysiological brain stereotactic method was used to test long-term potentiation (LTP) in dentate gyrus (DG) of the rats. An in-depth study in the relationship between Ng signal transduction pathway and SD damages cognitive function was done through real-time fluorescence quantitative PCR, Western blot, immunohistochemical techniques. It has been reported that Ng is one of the target genes regulated by retinoic acid (RA)-the active metabolite of VA and thyroid hormone (Triiodothyronine, T3). RA and T3 regulate the expression of gene through their corresponding nuclear receptor. Therefore we observated the roles of RA and T3 in protecting the damagment of cognitive function by SD in this study, and confirmed the important role of Ng in the peocess of SD damaged cognitive function. The results of this study may help to clarify the mechanisms in impairmentof cognitive function by SD furtherly and might provide theorical reference in preventing measures. The main findings are as follows:1. Observation the effects of SD to neurobehavior and cognitive function.Male Wistar rats were used in this study. After adapted to environment for one week, the animals were randomly divided into three groups: 24h, 48h and 72h experimental group. Each group was divided into sleep deprivation group (SD group) and control group (C group) (n=8 for each group). SD model was established by sleep deprivation box.The number of rearing was increased significantly after 24h and 48h SD (P <0.05) in OFT, and the number of crossing was in upward trend, indicating that spontaneous behavior and exploration activity was increased of rats, the excitement of central nervous system was enhanced, and showing early anxiety symptoms. With the sleep deprivation period was extended to 72h, the number of crossing was reduced obviously (P <0.05), showing that the excitement of the nervous system was switched from enhancement to inhibition.The amplitude of population spike (PS) was no significant difference between SD group and C group (P> 0.05) before high-frequency stimulation (HFS). The PS in the three SD groups were significantly lower than those of the C groups respectively (P <0.05), which indicated that the function of hippocampus was damaged by SD, likely through restraining the synaptic plasticity and excitability of neurons.2. Involvement of Ng and signal transduction pathways in the effects of SD on the cognitive function.The expression of NR1 mRNA in hippocampus of SD group was lower than that of C group after 24h and 48h SD,and significantly lower after 72h SD (P<0.05); The expression of NR2A mRNA of SD group was lower than that of C group after 48h SD,and significantly lower after 72h SD (P<0.05); The expressions of NR2B mRNA in hippocampus after 24h, 48h and 72h SD weren't changed. The expressions of NR1 and NR2A mRNA in prefrontal cortex weren't changed after 24h SD, and were lower than those of C groups after 48h and 72h SD,in which the expression of NR2A was significantly lower after 72h SD(P<0.05); The expressions of NR2B mRNA in prefrontal cortex after 24h, 48h and 72h SD weren't changed either. These indicaded the expressions of NR1 and NR2A mRNA were down regulated by SD. The levels of Ng mRNA in the hippocampus of 24h, 48h and 72h SD groups were lower obviously (P <0.05), also the expression of PKC and CaMKâ…¡mRNA were lower distinctly after 48h and 72h SD (P <0.05). Besides, The levels of Ng, PKC,CaMKâ…¡mRNA in prefrontal cortex of SD group were lower after 24h and 48h SD,and significantly lower only after 72h SD (P <0.05). The results were shown that the expressions of Ng, PKC and CaMKâ…¡in the hippocampus and prefrontal cortex were lower obviously. And the extent of reduction was more obvious with the time of SD extended. Ng has been implicated in the modulation of postsynaptic signal transduction pathways and synaptic plasticity.The levels of Ng expression in the hippocampus were lower significantly after 24h, 48h and 72h SD (P <0.05). The Ng protein expression level of prefrontal cortex in 72h SD group was striking decreased compared with C group coordinately (P<0.05).3. Effects of increase the expression of Ng on alleviating the impairment of cognitive function by SD.Experimental animals were randomly divided into four groups: 72h C group, 72h SD+NaCl group, 72h SD + RA group and 72h SD + T3 group. RA or T3 was injected intraperitonealy one day before SD in the intervention groups (150 g / kg). 1 times / day, continuing four days.The expressions of Ng protein in hippocampus and prefrontal cortex of 72hSD + RA and 72hSD + T3 groups were significantly higher than that of 72h SD group (P <0.05). There was no significant difference between them and C group. The number of rearing was in upward trend and the number of crossing was increased obviously (P <0.05) in OFT after administration of RA and T3. The amplitude of PS was significantly higher (P <0.05; P <0.01), and there was no significant difference between them and C group.In short, SD might affect signal transduction pathway in which Ng as the upstream regulation of important brain regions. This may damage learning and memory function. Thus, Ng might be a potential target for curative therapeutic attempts to improve cognitive function and working efficiency, and protect the health of the professional population. |
