Electrophysiological study of hepatic vagal projection to the medulla.

Medullary projection of the hepatic branch of vagus was examined electrophysiologically. Analysis of compound field potentials elicited by the hepatic vagal stimulation revealed that this nerve branch projects dominantly in the left side of the medulla. Afferent neurons in the solitary tract nucleus were identified by the electrical stimulation of the nerve branch. A collision test was also employed to separate the afferent from the efferent. Some afferent neurons which innervate the liver were responsive to the portal infusion of isotonic glucose solution, hypertonic saline and water. Their response patterns were almost similar to those of the hepatic afferent nerves.