The effect of vagal nerve stimulation on net fluid transport in the small intestine of the cat.

The effect of electrical vagal nerve stimulation on intestinal net fluid transport rate was studied in the small intestine of the cat. The splanchnic nerves were severed in all experiments. Absorption was quantified with a new gravimetric technique which made it possible to study fluid transport also during intestinal motility. The stimulation characteristics were varied to activate selectively low threshold fibres or low and high threshold fibres. The observations did not reveal any affects of low threshold stimulation on intestinal fluid transport whereas an inhibition was seen when also the high threshold fibres were stimulated. This inhibitory vagal mechanism could also be elicited after the administration of atropine. Atropine in itself increased "resting" net fluid absorption. The results speak against a role for vagal cholinergic mechanisms in the control of net fluid absorption. There seem, however, to be tonically active intramural cholinergic pathways and noncholinergic inhibitory vagal neurons of unknown physiological significance.