Effects And Mechanisms Of Sleep Development And Rapid Eye Movement Sleep Deprivation In Infant On Adult Behavior

The theory of "sleep ontogenetic development" holds that early sleep development is crucial for the maturation of brain structure and function.It is necessary for the development of the central nervous system,sensory and motor systems in fetuses and newborns,and it is indispensable for the creation of memory and long-term memory neural circuits,as well as for maintaining brain plasticity throughout life.Sleep deprivation in early human life can lead to adult emotional disorders(such as anxiety,depression,and autism),cognitive disorders(such as attention and psychology),and diseases such as obesity.In humans,obtaining clinical neonatal EEG data is difficult due to lack of parental support,which hinders related research.In animal studies,research on neonatal rats has been fragmented due to issues such as feeding and thermoregulation during the lactation period,resulting in fragmented sleep records.So far,it has been established that both humans and animals predominantly exhibit rapid eye movement(REM)sleep during early life,with non-rapid eye movement(NREM)sleep gradually emerging with development.However,the specific details of the composition and development of early life sleep structure,as well as the role of early life REM sleep and its reduction in affecting adult sleep structure,emotional behavior,neuronal development,and neurotransmitter changes,remain unclear.Therefore,in this study,we plan to:(1)build a combined multi-channel sleep recording system for pre-weaning life support in juvenile rats;(2)use this system to record and analyze sleep development,spectral changes,and circadian rhythms in rats from postnatal days P11-P75;(3)deprive rats of REM sleep during critical developmental stages P8-P21 using clomipramine(CLO),and evaluate changes in their adult sleep and emotional behavior,as well as changes in the morphology of serotoninergic neurons in the dorsal raphe nucleus and neurotransmitter content in the brain.This is intended to address the technical difficulties and scientific questions mentioned above.Results:(1)In newborn rats reared in our self-designed combined multi-channel sleep recording system for pre-weaning life support,the maximum feeding rate of the feeding tube gradually increased(from 0.250 ml/min to 0.625 ml/min)and the total amount of formula milk fed per day also increased gradually(from 6.0 ml/day to 12.0ml/day)as postnatal age increased from P9 to P16.The incubator temperature for maintaining stable sleep behavior of the pups gradually decreased(from 36°C to 30°C).There were no significant differences in body weight gain and hair growth between artificially reared animals and those nursed by their mothers at each postnatal age.(2)The ontogenetic features of sleep-wake states displayed that the proportion of REM was 57% and 59% and NREM sleep was 5.2% and 4.9 respectively,in dark and light phase at P11,and then REM sleep progressively decreased and NREM sleep increased with age.At P75,REM sleep in dark and light phase respectively,reduced to6.3% and 6.9%,while NREM correspondingly increased to 37% and 58%.Wakefulness from P11 to P75 in dark phase increased from 37% to 56%,but the change in light phase was not obvious.Awakening,NREM,and REM sleep,the amplitudes of the EEG waves during these three sleep phases gradually increase with postnatal age,reaching a stable level around P15-P16.The EEG,EMG,and EOG waveforms during sleep-wake cycles become more similar to those of adults.The circadian rhythm of sleep-wake cycles forms around P17-P18.In mice,there is a unique neck muscle electromyographic burst(Twitch)that occurs with accompanying limb and tail muscle twitches during sleep,under a background of extremely low electromyographic activity.The frequency of Twitch behavior decreases with increasing postnatal age,and Twitch behavior disappears completely after P23 in rats.REM sleep decreases significantly,and NREM sleep gradually increases with age.The number of fragments during dark and light periods decreases gradually,while the duration of fragments increases significantly.The transition between Wake and REM sleep dominates at P11,then decreases sharply,and eventually disappears in rats older than P30.From P11-P12,the total energy of Wake,NREM,and REM fragments is mainly concentrated in the 1-6 Hz range.The spectral power of Wake from P11-P75 increases significantly,mainly in the1-8 Hz range.The increase in delta waves(1-2 Hz)in NREM sleep is most significant.The development of theta rhythms during REM sleep is unique,with a significant increase in frequency bands from 4-5 Hz at P13 to 7-8 Hz at P75,showing an increasing trend in both energy and frequency.Although the absolute values of energy in different frequency bands increase during development,the percentage of delta spectral power decreases,while the percentage of theta spectral power increases.(3)Deprivation of REM sleep in P8-P21 neonatal mice with CLO drugs results in an increase in REM sleep in adult(P75)rats.The main characteristics are an increase in the number of REM sleep fragments,especially long fragments(>160s,320 s,>320s),and sleep disorders characterized by disrupted circadian rhythm of sleep-wake cycles and fragmented sleep.It also results in depression-like behaviors in adulthood,including increased immobility time in forced swimming test,decreased swimming and climbing time,and decreased preference for sucrose in sucrose preference test.Neurotransmitter analysis in adult rats fed with CLO during infancy(P75)compared to control group animals showed a significant decrease in the levels of histamine,serotonin,norepinephrine,dopamine,and glutamate,and a significant increase in the levels of gamma-aminobutyric acid(GABA)and tryptophan.Sholl analysis results showed that the total number of intersections in the CLO group decreased significantly(from 60 ± 12 to 50 ± 9,P < 0.05)compared to the control group.The total dendritic length of 5-HT neurons in the median raphe nucleus was significantly lower in the CLO group than in the control group(670.09 ± 26.76 vs.5554.61 ± 21.18,P < 0.05).The increase in primary branches(274.18 ± 28.33 vs.280.17 ± 32.35,P > 0.05)and the decrease in main trunk/secondary branch length(323.41 ± 28.91 vs.245.71 ± 34.18,72.20 ± 19.58 vs.37.66 ± 16.69,P > 0.05)did not reach statistical significance.Conclusion: Our self-designed and constructed neonatal rat life support combined with multi-channel sleep recording system effectively supports the growth and development process of pre-weaning neonatal rats.With increasing age,REM sleep decreases,while NREM sleep increases and dominates the sleep duration in the later stage of development.Overall energy expenditure shows a gradual increase with age.During the developmental process,the percentage of delta power decreases,while the percentage of theta power increases.Deprivation of REM sleep in neonatal rats can lead to adult-like depressive behavior and sleep disorders,possibly due to alterations in the morphological development of serotonin neurons and significant reduction in monoamine neurotransmitter levels due to the absence of REM sleep during early life.