The importance of nervous and humoral factors in the control of vascular resistance, blood flow distribution and net fluid absorption in the cat small intestine during hemorrhage

The influence of preganglionic (splanchnic) and postganglionic (periarterial) denervation of the cat small intestine on the changes in blood flow and net fluid absorption elicited by hemorrhage was investigated. The compiled data from a previous report indicate that hemorrhage induces a vasoconstriction and a redistribution of blood flow towards the absorptive part of the mucosa. The vasoconstriction was unaffected by a total postganglionic denervation whereas after a preganglionic denervation both the vasoconstriction and the redistribution of blood flow were abolished. We have also shown earlier that hemorrhage induced an increase in net fluid absorption as long as no ischemic mucosal lesions developed. This increase was reduced by postganglionic denervation, and was reversed into a small decrease after preganglionic denervation. On the basis of these findings it is proposed that the increase in vascular resistance, the redistribution of blood flow towards the absorptive part of the mucosa as well as the increase in net fluid absorption observed after hemorrhage all are effects mainly mediated via the splanchnic nerves. Furthermore, humoral factors are of major importance for the increase in vascular resistance observed after hemorrhage. The increase in net fluid absorption was shown to be induced both by direct nervous and by humoral factors.