Evidence for separate sympathetic regulation of fluid absorption and blood flow in the feline jejunum.

Splanchnic nerve stimulation (SNS) in cats leads to a jejunal vasoconstriction and to an enhancement of jejunal net fluid absorption. We tested the possibility that the sympathetic fibers to the transporting epithelium might use a ganglionic transmission mechanism different from the one utilized by the jejunal vasoconstrictor nerves. The splanchnic nerves were stimulated before and after a dose of hexamethonium sufficient to entirely block the intestinal vasoconstrictor fibers. However, SNS still increased net fluid absorption in these hexamethonium-treated animals. The hexamethonium-resistant increase in fluid absorption during SNS was a neurogenic effect on the jejunal segment, as it was eliminated by mesenteric denervation and could be reproduced by stimulation of the nerves surrounding the superior mesenteric artery. These data indicate that the rate of jejunal fluid absorption may be regulated by sympathetic fibers functionally distinct from the intestinal vasoconstrictor nerves.