Involvement of sympathetic function in the sleep-related change of gastric myoelectrical activity in rats

Abstract

SUMMARYThe gastric myoelectrical activity (GMA) fluctuates across sleep-wake states as a result of modulation by the brain-gut axis. The role of the autonomic nervous system in this phenomenon, however, was not elucidated fully. Through simultaneous recording and subsequent continuous power spectral analysis of electroencephalogram, electromyogram, electrocardiogram and electrogastromyogram (EGMG) in 16 freely moving Wistar rats, the sleep-wake states of the animals were defined and indices of cardiac autonomic regulation and GMA were calculated. We found that both cardiac autonomic regulation and GMA fluctuated through sleep-wake cycles. Correlation analysis further revealed significant correlations between EGMG power and each of the R-R interval, high-frequency power, low-frequency power, very-low-frequency power, low-frequency power to high-frequency power ratio and normalized low-frequency power of heart rate variability with respect to their trend of change across different sleep-wake states. These results suggest that the sleep-wake-related change of GMA was related to sympathovagal balance. The sympathetic nerve may play a more important role in the central modulation of GMA than perceived previously.k e y w o r d s brain-gut axis, gastric myoelectrical activity, heart rate variability, rat, sleep

The influence of autonomic interventions on the sleep-wake-related changes in gastric myoelectrical activity in rats

“…In this study, the range of the EGMG dominant frequency was similar to that reported in previous studies, 26,43 in which the sleep–wake states of the study subjects were not defined. In our previous study using Wistar rats, however, the frequency of gastric slow wave was slightly but significantly lower during QS 20 . This phenomenon was not observed in this study and might be ascribed to the different strain of rat used.…”

“…Fluctuations in EGMG power across the various sleep–wake states were observed in all four experimental groups, but the extent and pattern were different. In the Sham group, the power during AW was significantly higher than during the other two states, while the power during PS was significantly higher than during QS, as was reported in our previous study 20 . Either vagotomy or chemical sympathectomy alone did not abolish this pattern of change as it was preserved in both the TV and Sham + 6‐OHDA groups.…”

“…In our previous research, we studied the correlation between cardiac autonomic activity and electrogastromyogram (EGMG) power across sleep–wake transitions in freely moving rats. The results suggested that the sleep–wake‐related fluctuations in EGMG power were under the joint modulation of the both limbs of the ANS 20 . The result was inferential, however, and more substantial evidence is required to elucidate the underlying mechanisms.…”

“…On the day after completion of the injections, the rats underwent the operation needed for the future sleep studies. The details of the surgical procedure have been described previously 20–22 . In brief, each rat was anesthetized with intraperitoneal pentobarbital (50 mg kg −1 ) and placed in a standard stereotaxic apparatus where electrodes for parietal electroencephalogram (EEG) and nuchal electromyogram (EMG) were implanted.…”

“…Power spectral analysis was then accomplished by fast Fourier transformation after application of the Hamming window. For each 16‐s time segment, the power of the EMG spectrogram (200–500 Hz) and the power of the EGMG spectrogram (0.067–0.1 Hz) were quantified by the method of integration 20,26 . Power spectral analysis was also used to determine the EGMG dominant frequency.…”