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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Colon, Diffusion Chambers, Culture, Dose-Response Relationship, Drug, Drug Synergism, Estradiol, Female, Gastrointestinal Motility, Hormone Antagonists, Magnesium, Muscle Contraction, Muscle, Smooth, Oxytocin, Progesterone, Rabbits, Receptors, Oxytocin, Tetrodotoxin, Vasotocin.
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Are the inhibitory effects of oxytocin on distal colonic contractile activity in rabbits enhanced by ovarian steroids? Context: To study the effects of oxytocin on isolated rabbit distal colon and the regulation of ovarian steroids by its action. Muscle strips parallel to either the circular or the longitudinal fibres were excised and suspended in tissue chambers containing 5 mL Krebs solution (37 degrees C) and bubbled continuously with 95% O(2) and 5% CO(2). The effects of oxytocin on isometric spontaneous contractile responses were recorded. The effects of atosiban, tetrodotoxin, Mg(2+), progesterone and oestradiol on the oxytocin-induced response were also examined. Oxytocin (1, 10 and 100 nmol L(-1)) dose dependently decreased the area under the contraction curve of distal colonic smooth muscle strips. The oxytocin receptor antagonist atosiban blocked the oxytocin (10 nmol L(-1))-caused responses in a dose-dependent manner. Tetrodotoxin (10 micromol L(-1)) had no effect on the oxytocin-induced response. Mg(2+)-free Krebs solution attenuated the oxytocin-induced response, but oestradiol (0.1 micromol L(-1)) or progesterone (0.1 micromol L(-1)) increased the oxytocin-induced response.
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These results suggest that oxytocin inhibits the contractile motility of the distal colon, which is regulated by Mg(2+) and ovarian steroids. Final Decision: yes