Afferent impulses in the vagal and splanchnic nerves of toad's stomach, and their role in sensory mechanism.

Abstract

The function of the vagal and splanchnic afferent system of the stomach was compared by recording afferent impulse discharge from nerve trunks or single nerve fibers during mechanical stimulation of the stomach of the toad. The results are summarized as follows:1. The receptive fields of single vagal afferent fibers were far smaller than those of splanchnic fibers. The former was localized in the cardiac portion and the latter along the lesser curvature.2. There were three groups of the nerve fibers in reference to their diameters. Vagal afferent fibers belong to the medium group and splanchnic fibers belong to small or large diameter groups.3. The adaptation of vagal mechano-receptors was rapid and that of splanchnic mechano-receptors was relatively slow in general.4. The vagal receptors were excited by passive distension and active contraction of the stomach. The splanchnic receptors responded only to extreme distension of the stomach wall and traction of stomach mesentery.5. It was found that vagal gastric mechano-receptors are situated in the mucosa or submucosa of the gastric wall and splanchnic mechano-receptors are in the serosa or subserosa.It is concluded that the function of vagal afferent fibers from gastric mechano-receptors is to signal the mechanical deviation of the gastric wall related to fullness or hunger sensations and that of splanchnic receptors is to signal pain or other sensation.