Abstract
Abnormal colonic motility may be associated with dysfunction of the autonomic nervous system (ANS). Our aim was to evaluate if associations between colonic motor patterns and autonomic neural activity could be demonstrated by assessing changes in heart rate variability (HRV) in healthy volunteers. A total of 145 colonic motor patterns were assessed in 11 healthy volunteers by High-Resolution Colonic Manometry (HRCM) using an 84-channel water-perfused catheter. Motor patterns were evoked by balloon distention, a meal and luminal bisacodyl. The electrocardiogram (ECG) and cardiac impedance were assessed during colonic manometry. Respiratory sinus arrhythmia (RSA) and root mean square of successive differences of beat-to-beat intervals (RMSSD) served as measures of parasympathetic reactivity while the Baevsky’s Stress Index (SI) and the pre-ejection period (PEP) were used as measures of sympathetic reactivity. Taking all motor patterns into account, our data show that colonic motor patterns are accompanied by increased parasympathetic activity and decreased sympathetic activity that may occur without eliciting a significant change in heart rate. Motor Complexes (more than one motor pattern occurring in close proximity), High-Amplitude Propagating Pressure Waves followed by Simultaneous Pressure Waves (HAPW-SPWs) and HAPWs without SPWs are all associated with an increase in RSA and a decrease in SI. Hence RSA and SI may best reflect autonomic activity in the colon during these motor patterns as compared to RMSSD and PEP. SI and PEP do not measure identical sympathetic reactivity. The SPW, which is a very low amplitude pressure wave, did not significantly change the autonomic measures employed here. In conclusion, colonic motor patterns are associated with activity in the ANS which is reflected in autonomic measures of heart rate variability. These autonomic measures may serve as proxies for autonomic neural dysfunction in patients with colonic dysmotility.
Highlights
Colonic motility is regulated by a multitude of control systems
The ability of the Autonomic Nervous System (ANS) to facilitate the generation of colonic motor patterns, may be related to a person’s general autonomic reactivity (Shaffer and Ginsberg, 2017), which was measured
Pre-Ejection Period (PEP) did not show any significant change in response to posture change (Figure 2D)
Summary
Colonic motility is regulated by a multitude of control systems. The colonic musculature receives rhythmic depolarization from the colonic pacemaker networks of interstitial cells of Cajal (ICC) and on-demand depolarization from the enteric nervous system (Furness, 2012; Huizinga, 2018). The extrinsic nervous system facilitates brain – colon communication, which plays a critical role in many aspects of colonic motility such as the defecation reflex (Szurszewski et al, 2002; Tache, 2003; Brookes et al, 2016). The defecation reflex starts with a sensation of urgency mediated by rectal stimulation followed by sacral sensory nerve activation. This impulse initiates activity in the sacral defecation center, which sends signals to brain stem areas and the frontal cortex, which in turn activate motor nerves from the ANS and the enteric nervous system to produce a bowel movement (Furness, 2012; Spencer et al, 2016). Attempts have been made to gain insight into brain-gut communication through analysis of heart rate variability (HRV); Irritable Bowel Syndrome (IBS) patients with constipation appear to have decreased levels of resting parasympathetic activity or increased resting sympathetic activity, suggesting that parasympathetic withdrawal with or without sympathetic activation could be an important contributing factor to constipation (Mazurak et al, 2012; Polster et al, 2018)
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