The role of the autonomic nervous system (ANS) in control of colonic motility is unclear. Measurement of heart rate variability may provide diagnostic information for patients with colonic dysmotility. We explored relationships between the cardiac output of the ANS through heart rate variability (HRV) and colonic motor patterns with or without sensation during high-resolution colonic manometry (HRCM) Ten healthy volunteers (33 ± 12 yrs; 6 male) received HRV testing in response to body position changes (supine, sitting, standing, walking). 4 weeks later HRCM was performed with synchronized HRV recording. The parasympathetic and sympathetic reactivities were evaluated by Respiratory Sinus Arrhythmia (RSA) and the Pre-Ejection Period (PEP) respectively. Colonic motor patterns were recorded at baseline and under provoking conditions: balloon distension, a meal and luminal bisacodyl To assess general parasympathetic and sympathetic tone, body position change from supine condition to walking showed a decline in RSA from 6.7 ± 0.8 to 5.4 ± 0.7 (P<0.05), suggesting a decrease in parasympathetic activity; the PEP did not show significant change from 123.2 ± 20.0 to 113.3 ± 16.5 (P>0.05). Colonic motor complexes, multiple high amplitude pressure waves (HAPWs) with or without simultaneous pressure waves (SPWs)(n=47), were induced by balloon distention or luminal bisacodyl. During their occurrence, RSA was increased from 6.7 ± 1.2 to 7.5 ± 1.1 (P<0.001) and PEP was increased from 110.5 ± 15.3 to 116.3 ± 14.2 (P<0.0001), suggesting increased parasympathetic tone and decreased sympathetic tone. No significant autonomic change was observed during the occurrence of isolated HAPWs or SPWs. During HAPWs associated with SPWs and internal anal sphincter relaxation (n=30), RSA increased from 6.3 ± 1.1 to 6.8 ± 1.1 (P=0.005) and PEP did not show significant change (118.2 ± 11.1 to 121.4 ± 10.1; P=0.022), suggesting increased parasympathetic tone. In terms of the appreciable sensation (urge, discomfort, pain) during the occurrence of the motor pattern, both groups (109 out of 159 motor patterns with sensation and 50 out of 159 without sensation) showed increased RSA (from 6.4 ± 1.2 to 7.1 ± 1.2 and from 6.5 ± 1.2 to 6.9 ± 0.9, respectively; P<0.0001) and increased PEP (from 113.19 ± 14.90 to 115.5 ± 13.9, from 116.9 ± 10.43 to 119.32 ± 12.1, respectively; P<0.0001). There was no significant difference in RSA or PEP changes between these two groups (P>0.05), suggesting that is was motor activity that induced autonomic changes. Colonic motor complexes and HAPWs associated with SPWs, but not isolated HAPWs or SPWs, are associated with increased parasympathetic tone and decreased sympathetic tone, measured as increased RSA and PEP respectively. The associated sensation is not reflected in ANS changes. A colonic motor complex (2 high amplitude pressure waves (HAPWs) associated with 2 simultaneous pressure waves (SPWs) and IAS relaxation) was associated with an increase in RSA and a decrease in heart rate. CIHRHamilton Academic Health Sciences Organization and the Canadian Foundation of Innovation Evans Leadership Fund