The effects of combined distension of the stomach and the descending colon on coronary blood flow in anaesthetized pigs

The effects of the combined distension of the stomach and the descending colon on coronary blood flow were examined in seven α-chloralose anaesthetized pigs whilst preventing changes in heart rate and aortic blood pressure. Changes in coronary blood flow in the left circumflex or anterior descending coronary artery were assessed using electromagnetic flowmeters during distension with Ringer solution of balloons positioned 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 l always caused graded decreases in coronary blood now. The additional distension of the descending colon at a distending volume of 0.25 l augmented the response of decrease in coronary blood flow caused by the first two 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 stomach at a volume of 0.8 l was additionally performed during graded distension of the descending colon with distending volumes of 0.25, 0.35 and 0.45 l. These effects elicited by combined distension of the two viscera were not affected by the administration of propranolol, but they were abolished by subsequent administration of phentolamine. The results showed that combined distension of the stomach and the descending colon in anaesthetized pigs augmented the reflex response of coronary vasoconstriction and that the response to distension of one viscus was attenuated during increased levels of distension of the other viscus. These combined responses to distension of the two viscera involved efferent sympathetic mechanisms related to α-adrenoceptors.