Reflex regional vascular responses during passive gastric distension in cats

The increase in systemic vascular resistance during gastric distension in cats may result from variable vasomotor responses in several parallel regional vascular beds. Accordingly, in 23 anesthetized cats the stomach was passively distended with a balloon while systemic hemo-dynamics were monitored. Regional vascular responses were determined during control periods and during gastric distension either by injection of radioactive microspheres (15 cats) or by constant perfusion of vascularly isolated organs (8 cats). During distension, mean arterial pressure and systemic vascular resistance increased by 32 and 28%, respectively. Regional flow measurements indicated no significant alterations in any of the organs examined. Calculated regional vascular resistances indicated vasoconstriction in the kidneys (53%), small intestine (31%), and large intestine (37%) that was reversed by alpha-adrenergic blockade with phentolamine. Constant-flow perfusion studies confirmed the regional vasoconstriction in the renal, superior mesenteric, and hindlimb circulations. These studies suggest a regional heterogeneity of vasomotor response during passive gastric distension in cats that includes no change in vascular resistance in some organs and alpha-adrenergic vasoconstriction in others.