Endogenous oxytocin excites phasic contraction of gallbladder in rabbits through oxytocin receptor.
These experiments were performed to study the effect of oxytocin (OT) and it's specific receptor on gallbladder motility in rabbits. The fasted New Zealand white rabbits (2.0-2.5 kg) were anaesthetized by urethane (1 g/kg). The gallbladder pressure was recorded continuously to monitor the gallbladder motility. Systemic OT (0.01, 0.02, 0.04 mg/kg, iv) did not affect the gallbladder pressure, but dose-dependently increased the frequency of phasic contraction. Five min after OT administration (0.04 mg/kg, iv), the strength of phasic contraction increased to 0.23 +/- 0.08 mmHg/min (P < 0.01, n = 6). The gallbladder motility returned to normal 15 min later after OT treatment. Intravenous injection of atosiban (0.04 mg/kg, iv), an OT receptor antagonist, decreased the strength of gallbladder phasic contraction but did not affect gallbladder pressure. Pretreatment of atosiban (0.04 mg/kg, iv) completely abolished the systemic OT effect on gallbladder. Vasopressin (VP) (0.1 - 0.5 IU/kg, iv) dose-dependently decrease the gallbladder pressure but did not affect the phasic contraction. MK-329 (0.4 mg/kg, iv), the CCK-A receptor antagonist, L-365, 260 (0.4 mg/kg, iv), the CCK-B receptor antagonist and atropine (0.2 mg/kg, iv), the M receptor antagonist, did not affect the OT effect on gallbladder motility. We suggest that endogenous OT regulates gallbladder phasic contraction through specific OT receptor. This effect is independent of the peripheral CCK and M receptors.
Liu
Chuan-Yong
CY
Institute of Physiology, Medical School of Shandong University, Jinan, Shandong, PR China. liucy@sdu.edu.cn
Liu
Jing-Zang
JZ
Xie
Dong-Ping
DP
Liu
Pei-Yi
PY
Wang
Paulus S
PS
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D005260:Female; D016473:Gallbladder Emptying / Q000187:drug effects / Q000502:physiology*; D006727:Hormone Antagonists / Q000494:pharmacology; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010121:Oxytocin / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors; D018045:Receptors, Oxytocin / Q000037:antagonists & inhibitors / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology; D014668:Vasotocin / Q000031:analogs & derivatives* / Q000494:pharmacology
D006727:Hormone Antagonists; D018727:Muscarinic Antagonists; D011949:Receptors, Cholecystokinin; D018045:Receptors, Oxytocin; D014662:Vasoconstrictor Agents; C047046:atosiban; D014667:Vasopressins; D010121:Oxytocin; D001285:Atropine; D014668:Vasotocin