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The importance of fetal/neonatal REM sleep
Insights
Early life rapid-eye movement (REM) sleep is crucial for normal brain development. REM deprivation in infant rats led to lasting behavioral and cognitive deficits in adulthood, highlighting risks from medications affecting sleep.
Area of Science:
- Neuroscience
- Developmental Biology
- Behavioral Science
Background:
- Behavioral state emergence is key in development.
- Newborn rats exhibit immature central nervous system (CNS) development and poorly organized sleep states.
- Infant rat sleep shows high motor activation and rapid eye movements (REM), with increased neuronal activation.
Purpose of the Study:
- To investigate the functional significance of REM sleep during early development.
- To determine the long-term effects of REM sleep deprivation in early life on adult brain and behavior.
Main Methods:
- Rat pups were deprived of REM sleep between 1 to 3 weeks of age.
- Adult rats were tested for behavioral and cognitive functions after early-life REM deprivation.
- Studies also involved instrumental, surgical, and pharmacological methods to suppress REM sleep.
Main Results:
- Chronic REM sleep suppression in early development induced hyperactivity, hyperanxiety, and attentional deficits in adult rats.
- Reduced sexual performance and smaller cerebral cortical size were observed in REM-deprived adults.
- Similar adverse effects on brain and behavior were found across different methods of REM suppression.
Conclusions:
- REM sleep plays a critical role in normal brain and behavioral development.
- Reduced REM sleep or disturbed monoamine activity during early life poses significant risks.
- Caution is advised regarding medications or conditions impacting REM sleep and monoamine activity in prenatal and early postnatal life.
Abstract:
The emergence of behavioral states is one of the most significant aspects of development. The rat is very immature at birth and in some structural and functional aspects of CNS (central nervous system) development it is comparable to a 7-month-old human fetus. At this stage of development synchronization of different state criteria is poorly organized. Infant rats spend very little time in wakefulness and, once asleep, they still display a very high level of motor activation, with frequent rapid eye movements and uncoordinated myoclonic jerks. Although it is questioned whether the activated state of sleep in the newborn rat is comparable to rapid-eye movement sleep (REM) in adults, it has been shown that the CNS displays an increased level of endogenous neuronal activation even in very immature animals during this state. To study the functional significance of REM in early life, rat pups were deprived of this state from 1 to 3 wk of age and tested as adults. In the rat, chronic suppression of REM by interfering with monoamines during early development induced hyperactivity, hyperanxiety, attentional distractability, sleep disturbances, reduced sexual performance and reduced cerebral cortical size. In studies using instrumental, surgical or other pharmacological treatments to suppress REM similar effects on the development of brain and behavior were found. Taken together, these findings point to a role for REM during early development, so that more attention should be given to the potential hazards of medicines (and/or pathologic conditions) which induce reduced levels of REM and or disturbed monoamine activities in the brain during late prenatal and early postnatal life.