Effects of CPAP treatment on electroencephalographic activity in patients with obstructive sleep apnea syndrome during deep sleep: Preliminary findings of a cross-sectional study

Study objectives: To investigate whether electroencephalographic (EEG) activities during non-rapid eye movement sleep stage 3 (N3) in obstructive sleep apnea syndrome (OSAS) patients were changed with continuous positive airway pressure (CPAP) treatment.Methods: A cross-sectional study of EEG activity during N3 sleep was conducted in 15 patients with moderate to severe OSAS without and with CPAP treatment compared to 15 normal controls. The amplitude, and absolute and relative power of delta, theta, alpha and beta waves as well as the absolute power ratio of slow to fast EEG waves (i.e., absolute power of delta and theta waves/absolute power of alpha and beta waves) and the spectral power density of 0-30 Hz EEG activities were analyzed.Results: CPAP significantly increased N3 sleep, the absolute and relative powers, amplitudes of delta and theta waves, and absolute power ratio of slow to fast EEG waves, but decreased relative alpha and beta powers during N3 sleep. However, there were no significant differences in those parameters between the OSAS patients with CPAP treatment and normal controls.Conclusions: CPAP prolongs N3 sleep and increases the power and amplitude of slow EEG waves during N3 sleep, which indicates an improvement in sleep quality and further provides evidence for recommendation of CPAP treatment for OSAS patients.

Cellular Effects of Rhynchophylline and Relevance to Sleep Regulation

Uncaria rhynchophylla is a plant highly used in the traditional Chinese and Japanese medicines. It has numerous health benefits, which are often attributed to its alkaloid components. Recent studies in humans show that drugs containing Uncaria ameliorate sleep quality and increase sleep time, both in physiological and pathological conditions. Rhynchophylline (Rhy) is one of the principal alkaloids in Uncaria species. Although treatment with Rhy alone has not been tested in humans, observations in rodents show that Rhy increases sleep time. However, the mechanisms by which Rhy could modulate sleep have not been comprehensively described. In this review, we are highlighting cellular pathways that are shown to be targeted by Rhy and which are also known for their implications in the regulation of wakefulness and sleep. We conclude that Rhy can impact sleep through mechanisms involving ion channels, N-methyl-d-aspartate (NMDA) receptors, tyrosine kinase receptors, extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K)/RAC serine/threonine-protein kinase (AKT), and nuclear factor-kappa B (NF-κB) pathways. In modulating multiple cellular responses, Rhy impacts neuronal communication in a way that could have substantial effects on sleep phenotypes. Thus, understanding the mechanisms of action of Rhy will have implications for sleep pharmacology.

Sex differences in brain oscillatory activity during sleep and wakefulness in obstructive sleep apnea

Epidemiological studies consistently show a male predominance in obstructive sleep apnea (OSA). Hormonal differences, breathing control, upper airway anatomy and fat distribution have been proposed as causes of gender differences in OSA. Clinical manifestations are accentuated in men, although white matter structural integrity is affected in women. To the best of our knowledge, no previous studies have explored gender differences in the electrical brain activity features of OSA. Polysomnography was performed on 43 patients with untreated OSA (21 women, 22 men), and power spectral density (1-50 Hz) was compared between groups across sleep and wakefulness at two levels of OSA severity. Severe versus moderate OSA showed decreased power for fast frequencies (25-29 Hz) during wakefulness. OSA men displayed decreased power of a large frequency range (sigma, beta and gamma) during sleep compared with women. Comparisons of men with severe versus moderate OSA presented significantly decreased sigma power during non-rapid eye movement (NREM) sleep, but significantly increased delta activity during REM sleep. Meanwhile, women with severe versus moderate OSA showed no significant power differences in any condition. These findings indicated a different evolution of brain oscillations between OSA men and women with significant impairment of brain activity related to cognitive processes. Our study emphasizes the importance of understanding the differential effects of sleep disorders on men and women in order to develop more precise diagnostic criteria according to gender, including quantitative electroencephalogram (EEG) analysis tools.

Altered postnatal development of cortico-hippocampal neuronal electric activity in mice deficient for the mitochondrial aspartate-glutamate transporter

The deficiency in the mitochondrial aspartate/glutamate transporter Aralar/AGC1 results in a loss of the malate-aspartate NADH shuttle in the brain neurons, hypomyelination, and additional defects in the brain metabolism. We studied the development of cortico/hippocampal local field potential (LFP) in Aralar/AGC1 knockout (KO) mice. Laminar profiles of LFP, evoked potentials, and unit activity were recorded under anesthesia in young (P15 to P22) Aralar-KO and control mice as well as control adults. While LFP power increased 3 to 7 times in both cortex and hippocampus of control animals during P15 to P22, the Aralar-KO specimens hardly progressed. The divergence was more pronounced in the CA3/hilus region. In parallel, spontaneous multiunit activity declined severely in KO mice. Postnatal growth of hippocampal-evoked potentials was delayed in KO mice, and indicated abnormal synaptic and spike electrogenesis and reduced output at P20 to P22. The lack of LFP development in KO mice was accompanied by the gradual appearance of epileptic activity in the CA3/hilus region that evolved to status epilepticus. Strikingly, CA3 bursts were poorly conducted to the CA1 field. We conclude that disturbed substrate supply to neuronal mitochondria impairs development of cortico-hippocampal LFPs. Aberrant neuronal electrogenesis and reduced neuron output may explain circuit dysfunction and phenotype deficiencies.