REFLEX CORONARY VASOCONSTRICTION CAUSED BY GALLBLADDER DISTENSION IN ANESTHETIZED PIGS

Background Gallbladder distension in anesthetized pigs reflexly increa ses heart rate and arterial pressure by means of afferent vagal pathwa ys and efferent sympathetic mechanisms. The effect of such distension on the coronary circulation is unknown. The present study was undertak en to determine whether gall-bladder distension primarily causes refle x changes in left circumflex blood flow.Methods and Results In 21 pigs anesthetized with sodium pentobarbitone (16) or alpha-chloralose (5), left circumflex blood flow was measured with an electromagnetic flowm eter. A balloon positioned within the gallbladder was distended with v olumes of Ringer's solution equal to the volumes of bile previously wi thdrawn (mean vol: 62 mL; mean gallbladder pressure: 12 mm Hg). Heart rate and arterial pressure were kept constant by atrial pacing and by a pressurized reservoir connected to the left femoral artery. Gallblad der distension always caused a decrease in circumflex blood flow. In 6 of the 16 sodium pentobarbitone-anesthetized pigs, this decrease was graded by step increments of distension. In 5 of these 16 pigs, the de crease in circumflex blood flow was not affected by atropine. In 10 of these 16 pigs, including those given atropine, the response was not a ffected by propranolol but was abolished by subsequently giving phento lamine. Cervical vagotomy abolished the coronary vasoconstriction in t he remaining 6 pigs. In the 5 alpha-chloralose-anesthetized pigs, the response was not significantly affected by cutting the splanchnic nerv es but was abolished by subsequent cervical vagotomy. Conclusions The present study showed that innocuous distension of the gallbladder in a nesthetized pigs caused a reflex coronary vasoconstriction that involv ed efferent sympathetic mechanisms related to alpha-adrenoceptors and afferent vagal pathways.