THE EFFECTS OF COMBINED DISTENSION OF THE STOMACH AND THE DESCENDING COLON ON CORONARY BLOOD-FLOW IN ANESTHETIZED PIGS

The effects of the combined distension of the stomach and the descendi ng colon on coronary blood flow were examined in seven alpha-chloralos e anaesthetized pigs whilst preventing changes in heart rate and aorti c blood pressure. Changes in coronary blood flow in the left circumfle x or anterior descending coronary artery were assessed using electroma gnetic flowmeters during distension with Ringer solution of balloons p ositioned in the viscera. In a first set of studies, graded distension of the stomach with distending volumes of 0.8, 1.1 and 1.4 1 always c aused graded decreases in coronary blood flow. The additional distensi on of the descending colon at a distending volume of 0.25 1 augmented the response of decrease in coronary blood flow caused by the first tw o levels of gastric distension, but it did not have any further effect when added to the higher level of gastric distension. Similar results were obtained in a second set of studies in which distension of the s tomach at a volume of 0.8 1 was additionally performed during graded d istension of the descending colon with distending volumes of 0.25, 0.3 5 and 0.45 1. These effects elicited by combined distension of the two viscera were not affected by the administration of propranolol, but t hey were abolished by subsequent administration of phentolamine. The r esults showed that combined distension of the stomach and the descendi ng colon in anaesthetized pigs augmented the reflex response of corona ry vasoconstriction and that the response to distension of one viscus was attenuated during increased levels of distension of the other visc us. These combined responses to distension of the two viscera involved efferent sympathetic mechanisms related to alpha-adrenoceptors. (C) 1 997 Elsevier Science B.V.