Association of sleep impairments and gastrointestinal disorders in the context of the visceral theory of sleep

The Mysterious Island: Insula and Its Dual Function in Sleep and Wakefulness

In the recent sleep studies, it was shown that afferentation of many cortical areas switches during sleep to the interoceptive one. However, it was unclear whether the insular cortex, which is often considered as the main cortical visceral representation, maintains the same effective connectivity in both states of vigilance, or processes interoceptive information predominantly in one state. We investigated neuronal responses of the cat insular cortex to electrical stimulations of the intestinal wall delivered during wakefulness and natural sleep. Marked increase was observed in the number of insular neurons responding to this stimulation in sleep comparing to wakefulness, and enlarged amplitudes of evoked local field potentials were found as well. Moreover, most of the cells responding to intestinal stimulation in wakefulness never responded to identical stimuli during sleep and vice versa. It was also shown that applied low intensity intestinal stimulations had never compromised sleep quality. In addition, experiments with microstimulation of the insular cortex and recording of intestinal myoelectric activity demonstrated that effective insula-to-gut propagation also happened only during sleep. On the other hand, the same insular stimulations in wakefulness led to contractions of orofacial muscles. The evoked face movements gradually disappeared in the course of sleep development. These findings demonstrate that pattern of efficient afferent and efferent connections of the insular cortex changes with transition from wakefulness to sleep.

Acute Ramelteon Treatment Maintains the Cardiac Rhythms of Rats during Non-REM Sleep

Sleep curtailment negatively affects cardiac activities and thus should be ameliorated by pharmacological methods. One of the therapeutic targets is melatonin receptors, which tune circadian rhythms. Ramelteon, a melatonin MT1/MT2 receptor agonist, has recently been developed to modulate sleep-wake rhythms. To date, the sleep-promoting effect of ramelteon has been widely delineated, but whether ramelteon treatment physiologically influences cardiac function is not well understood. To address this question, we recorded electrocardiograms, electromyograms, and electrocorticograms in the frontal cortex and the olfactory bulb of unrestrained rats treated with either ramelteon or vehicle. We detected vigilance states based on physiological measurements and analyzed cardiac and muscular activities. We found that during non-rapid eye movement (non-REM) sleep, heartrate variability was maintained by ramelteon treatment. Analysis of the electromyograms confirmed that neither microarousal during non-REM sleep nor the occupancy of phasic periods during REM sleep was altered by ramelteon. Our results indicate that ramelteon has a remedial effect on cardiac activity by keeping the heartrate variability and may reduce cardiac dysfunction during sleep.

Correlation between sleep impairment and functional dyspepsia

Objective

Sleeping habits may greatly impact the prevalence of functional dyspepsia (FD). This study examined relationships between aspects of sleep impairment and FD.

Methods

This prospective study included university student volunteers. Following enrolment, FD was diagnosed based on the Rome IV criteria, dividing participants into an FD group or controls. The FD group was further subdivided into long-term (disease course >6 months) and short-term (disease course 3–6 months) FD groups. Participants completed the Pittsburgh Sleep Quality Index (PSQI), the Rome IV Diagnostic Questionnaire for Gastrointestinal Disorders in Adults, and a visual analogue scale (VAS).

Results

Out of 418 participants in total, sleep quality, latency, and duration, habitual sleep efficiency, sleep disturbances, sleep medication use, daytime dysfunction, and PSQI scores were higher in the FD groups versus controls. Components of PSQI scores emerged as risk factors, and were higher in the long-term versus short-term dyspepsia group. Moreover, these components were positively correlated with frequency/severity of postprandial distress syndrome and early satiation. Total PSQI scores were positively correlated with VAS scores.

Conclusion

Several PSQI components are associated with FD occurrence, symptom frequency, and symptom severity.