Involvement of the autonomic nervous system in colonic contractions in conscious Suncus murinus

Abstract

AbstractBackgroundColonic motility is regulated by various factors along the gut‐brain axis; however, detailed mechanisms are unknown. This study aimed to examine the involvement of the autonomic nervous system in colonic motility. Suncus murinus (suncus) is a small laboratory mammal suitable for gastrointestinal motility studies.MethodsColonic motility and concomitant feeding and defecation behaviors in vagotomized and reserpine‐administered suncus were recorded simultaneously for 24 h. Furthermore, we performed immunohistochemistry on tyrosine hydroxylase (TH) and in situ hybridization on corticotropin‐releasing hormone (CRH) in suncus brain. Additionally, we examined c‐Fos expression in the brain using immunohistochemistry in conscious suncus with colorectal distension.Key ResultsIn vagotomized suncus, clustered giant migrating contractions (GMCs), consisting of strong contractions occurring in a short time, were observed, and the percentage of GMCs without defecation increased. The frequency of GMCs in the reserpine‐administered suncus increased during a light period (ZT0‐4, 4–8) and decreased during a dark period (ZT16‐20, 20–24) compared to a vehicle group. Additionally, the percentage of GMCs without defecation in the reserpine‐administered suncus increased. Suncus TH‐immunopositive neurons were found in the locus coeruleus (LC), as shown in rodents. In contrast, CRH mRNA‐expressing cells were not observed in a region assumed to be the Barrington's nucleus (Bar). Furthermore, colorectal distension in conscious suncus induced c‐Fos expression in LC TH neurons.Conclusions & InferencesOur results suggest that the vagus and sympathetic nerves are not required for induction of GMCs in vivo. However, they are likely to exert a modulatory role in control of GMC frequency in Suncus murinus.