Cyclic alternating pattern in infants with congenital hypothyroidism.

Congenital hypothyroidism is defined as thyroid hormone deficiency present at birth which is crucial for brain development. Recently, the cyclic alternating pattern, a rhythm present in electroencephalography recordings in non-Rapid eye movement sleep, has been related to brain development and cognition in different pediatric conditions. Therefore, we evaluated the cyclic alternating pattern rate in infants with congenital hypothyroidism, thyroxine supplementation, and healthy controls. The parameters of the cyclic alternating pattern were evaluated in 19 healthy infants (10 female, mean age 25.5 ±â€¯15.5 months) and 21 infants diagnosed with congenital hypothyroidism (19 female, mean age 24.3 ±â€¯19.0 months). We considered the transient electro-cortical activations (phase A of the cycle) in non-Rapid eye movement sleep and the subdivisions of the A phase in: A1, A2 and A3, based on their frequency content. All subjects were subjected to polysomnography recording in a standard laboratory setting. Sleep data were stored computer following the International 10-20 System. Data showed that congenital hypothyroidism infants exhibited higher frequency of central apnea, hypopnea, and arousals in comparison to controls. Particularly, central apnea index decreased with age in the control group but not in congenital hypothyroidism group. Regarding to cyclic alternating pattern measurements, congenital hypothyroidism infants exhibit a higher frequency in the percentage of A3 subtype (electroencephalographic desynchrony) and conversely a lower percentage of A1 subtype (electroencephalographic synchrony), than healthy infants. An important finding of this study is the positive correlation between A1 mean duration and age, which is bigger in control group than in congenital hypothyroidism group (time duration in control group (0.52 s/month) versus congenital hypothyroidism group (0.1 s/month). Infants with congenital hypothyroidism showed an increase of A3 subtype, of central apnea, and of arousals. The reduction of percentage and mean duration of A1 subtype could be a valuable indicator of sleep development in patients with congenital hypothyroidism and healthy infants.

REM sleep loss and recovery regulates blood-brain barrier function.

The functions of rapid eye movement (REM) sleep have remained elusive since more than 50 years. Previous reports have identified several independent processes affected by the loss and subsequent recovery of REM sleep (hippocampal neurogenesis, brain stem neuronal cell death, and neurotransmitter content in several brain regions); however, a common underlying mechanism has not been found. We propose that altered brain homeostasis secondary to blood-brain barrier breakdown may explain all those changes induced by REM sleep loss. Therefore, the present report aimed to study the consequences of REM sleep restriction upon blood-brain barrier permeability to Evans blue. REM sleep restriction was induced by the multiple platform technique; male rats were REM sleep restricted 20h daily (with 4h sleep opportunity) during 10 days; control groups included large platform and intact rats. To study blood-brain barrier permeability Evans blue was intracardially administered; stained brains were sliced and photographed for optical density quantification. An independent experiment was carried out to elucidate the mechanism of blood-brain breakdown by transmission electron microscopy. REM sleep restriction increased blood-brain barrier permeability to Evans blue in the whole brain as compared to both control groups. Brief periods of sleep recovery rapidly and effectively restored the severe alteration of blood-brain barrier function by reducing blood-to-brain transfer of Evans blue. The mechanism of blood-brain barrier breakdown involved increased caveolae formation at brain endothelial cells. In conclusion, our data suggest that REM sleep regulates the physical barrier properties of the blood-brain barrier.

Role of sleep in the regulation of the immune system and the pituitary hormones.

Sleep is characterized by a reduced response to external stimuli and a particular form of electroencephalographic (EEG) activity. Sleep is divided into two stages: REM sleep, characterized by muscle atonia, rapid eye movements, and EEG activity similar to wakefulness, and non-REM sleep, characterized by slow EEG activity. Around 80% of total sleep time is non-REM. Although it has been intensely studied for decades, the function (or functions) of sleep remains elusive. Sleep is a highly regulated state; some brain regions and several hormones and cytokines participate in sleep regulation. This mini-review focuses on how pituitary hormones and cytokines regulate or affect sleep and how sleep modifies the plasma concentration of hormones as well as cytokines. Also, we review the effects of hypophysectomy and some autoimmune diseases on sleep pattern. Finally, we propose that one of the functions of sleep is to maintain the integrity of the neuro-immune-endocrine system.