A Study Of The Effect Of Maternal Sleep Deprivation On Emotional And Congnitive Function In Offspring And Its Mechanism

PART 1 Effects of sleep deprivation during pregnancy on the emotional and cognitive function in offspringsObjective:To investigate the effects of maternal sleep deprivation during different gestational periods on the emotional and cognitive functions in offsprings, gentle handling method was used to establish sleep deprivation model of pregnancy rats, and the behavioral tests were performed in young adult offspring rats (6-8 weeks).Methods:The pregnant Sprague-Dawley rats were randomly divided into four groups:control group, early maternal sleep deprivation group, middle maternal sleep deprivation group and late maternal sleep deprivation group. Sleep deprivation was carried out from 12 am to 6 pm each day with gentle handling for one week. All behavioral experiments were performed in young adult offspring rats aged 6-8 weeks. The anxiety-like behavior was tested with elevated plus maze and novelty-suppressed feeding test. Next, using forced swimming experiment, we tested the influence of maternal sleep deprivation on depressive-like behavior. Finally, the spatial learning and memory was assessed in the Morris water maze paradigm.Results:The offspring rats subjected to maternal sleep deprivation exhibited increased anxiety, as reflected by a decrease in entries and time in open arms during the elevated plus maze test and an increase in the latency to feeding during novelty-suppressed feeding test, compared with controls. During forced swimming test, the offspring rats subjected to maternal sleep deprivation displayed obvious depressive-like behavior since the latency to immobility significantly reduced and the immobility time significantly increased. In the Morris water maze test, the offspring rats subjected to maternal sleep deprivation exhibited markedly impairments of spatial learning and memory, as reflected by longer time in searching hidden-platform during spatial learning and less time spent in platform-located quadrant during spatial memory retrieval.Conclusion:Maternal sleep deprivation increased anxiety-and depressive-like behaviors and impaired spatial learning and memory in offspring rats.PART 2 A Study of the effect of maternal sleep deprivation on learning and memory ability in offspring and its mechanismObjective:To investigate the cellular mechanism underlying learning and memory impairment caused by maternal sleep deprivation, hippocampal neurogenesis and synaptic plasticity were examined in the present study.Methods:Immunofluorescent assay method:Firstly, the offspring rats (14 days old) were treated with BrdU (50mg/kg, i.p.) once a day for 7 consecutive days. Four weeks after the last BrdU administration, the animals were deeply anesthetized and transcardially perfused with 4% paraformaldehyde in 100 mM phosphate buffer. Immunofluorescent assay was conducted on 30μm coronal sections. To evaluate the survival of mature neurons in dentate gyrus of hippocapus, immunofluoresent double-labeling of brain sections with BrdU and NeuN (a neuronal marker) was used. To evaluate the survival of astrocytes, immunofluorescent double-labelings of brain sections with BrdU and GFAP (an astrocyte marker) was used. Secondly, the young adult offspring rats (6 weeks) were administered BrdU (100mg/kg,i.p.) three times in 24-h intervals. Twenty-four hours after last BrdU injection, the animals were deeply anesthetized and transcardially perfused with 4% paraformaldehyde buffer. Immunofluorescent assay was conducted on 30-μm coronal sections. Immunofluorescent assay was used to evaluate the cell proliferation in dentate gyrus of hippocapus. To observe newborn neurons, we used the early neuronal marker doublecortin (DCX) to stain the immature neurons. In addition, we used immunofluorescent double-labelings of brain sections with BrdU and either NeuN or GFAP to evaluate the proliferation of neuron or astrocyte, respectively.Electrophysiological experimental method:Firstly, we used in vivo electrophysiological recordings to examine the synaptic plasticity including hippocampal CA1 long-term potentiation (LTP) and long-term depression (LTD) in young adult offspring rats (aged 5-7 weeks). LTP and LTD were induced by high frequency stimulation (HFS) and low frequency stimulation (LFS), respectively. Secondly, acute hippocampal slices were prepared from the offspring rats (aged 5-7 weeks) for miniature excitatory postsynaptic currents (mEPSC).Results:Immunofluorescent assay results:We found that maternal sleep deprivation significantly reduced the Brdu+/NeuN+ cells, while Brdu+/GFAP+ cells remained unchanged. Furthermore, the number of DCX-expressing immature neurons was dramatically reduced in the DG of offspring rats subjected to maternal sleep deprivation. These results indicate that maternal sleep deprivation impairs adult hippocampal neurogenesis through reducing the neuronal survival and proliferation.Electrophysiological experimental results:maternal sleep deprivation significantly reduced hippocampal LTP and facilitated hippocampal LTD in offsprings. In addition, maternal sleep deprivation dramatically decreased mEPSC amplitude and frequency.Conclusion:These results suggested that neurogenesis impairment and the alteration of synaptic plasticity in the hippocampus may be one of the mechanisms underlying cognitive deficit caused by maternal sleep deprivation.