Effect of oxytocin on duodenal motility in female rats

ABSTRACT

Reports on the effect of oxytocin on intestinal motility have shown controversial results in human and animal studies. The aim of the study was to investigate the effect of oxytocin on duodenal motility in normal female Wistar rats in vivo and in vitro. A total of 30 adult female Wistar albino rats were divided into three groups the control group; the oxytocin-treated group [5 microg/kg body weight injected intraperitoneally for 7 days]; and the in-vitro oxytocin group, in which the effect of four doses of oxytocin [0.022, 0.11, 0.22, and 1.1 mg/bath] added to the organ bath was studied. The isometric contractile response of isolated segments of duodenum was recorded with respect to the frequency of contraction, the average duration of contraction, the average force of contraction, and the motility index. Oxytocin-treated rats showed a significant increase in the duodenum average force of contraction [P<0.05] and motility index [P<0.01] and a decrease in the frequency of contraction [P<0.05] as compared with the control group. Low doses of oxytocin administered in vitro [0.022 and 0.11 microg/bath] resulted in a significant increase in the duodenum average force of contraction [P<0.05] and motility index [P<0.05] when compared with their respective baseline values, whereas higher doses caused either insignificant changes in the motility parameters at a dose of 0.22 microg/bath or a significant decrease in the duodenum average force of contraction [P<0.01] and motility index [P<0.01] at a dose of 1.1 microg/bath when compared with their baseline values. Oxytocin treatment enhanced duodenal motility in adult female Wistar rats. Higher doses of oxytocin inhibit duodenal motility, which may be explained by an indirect mechanism