Rectal distension modulates canine gastric tone and accommodation

Rectal distension affects upper GI myoelectrical activity and motility. The aim of this experiment was to investigate the effect of rectal distension on gastric tone, accommodation, and the underlying mechanism. Seven healthy dogs were surgically prepared and studied. Gastric tone and accommodation were assessed with a barostat. In Experiment 1, the effect of rectal distension on gastric tone and accommodation was evaluated; in Experiment 2, rectal distensions with various volumes were randomly applied and its effects on gastric tone were evaluated; and in Experiment 3, the role of the cholinergic pathway in distension-induced gastric relaxation was assessed. The results showed the following. (1) Rectal distension exerted an inhibitory effect on gastric tone, and this response was distension volume-dependent. (2) Postprandial gastric volume was similar in the control (468.6 ± 24.7 ml) and the distension study (463.2 ± 17.5 ml). However, rectal distension increased the preprandial gastric volume, and subsequently decreased the extent of gastric accommodation (139.3 ± 34.7 ml), which was significantly lower than that of the control (383.2 ± 26.3 ml; P < 0.001). (3) An intravenous bolus of atropine increased the astric volume from the baseline of 89.4 ± 12.6 ml to 161.5 ± 9.8 ml (P < 0.01), and subsequent rectal distension further increased this volume, but the overall change was comparable between the control (297.6 ± 18.7 ml) and the atropine study (312.1 ± 21.9 ml; P > 0.05). In conclusion, rectal distension inhibits gastric tone in a volume-dependent manner and impairs gastric accommodation. Atropine dose not block the effect of rectal distension on proximal gastric tone, suggesting that the observed effect may not be mediated by cholinergic pathway.