A nervous mechanism for descending inhibition in guinea-pig small intestine.

1. Intracellular recordings were made from neurones in the myenteric plexus of guinea-pig small intestine under conditions in which these neurones received synaptic input from an adjacent segment of intestine.2. Most long synaptic pathways in the myenteric plexus were found to lead in an anal direction.3. Such pathways could be excited by either distension or transmural electrical stimulation of the intestinal segment.4. Similar stimuli evoked inhibitory junction potentials in the circular muscle layer but only on the anal side of the stimulated region of intestine.5. The results are discussed in relation to the concept of descending inhibition (Bayliss & Starling, 1899).