Gastro-intestinal tension receptors with unmyelinated afferent fibres in the vagus of the cat.

Abstract

1. Electrical activity was recorded in single afferent C fibres dissected from the cervical vagus of the cat. The receptors were distension‐sensitive endings in the œsophagus, stomach or small intestines. The latency of the response to distension was largely due to the time taken for the impulses to travel from the receptor to the recording electrodes.2. The rate of discharge of impulses was much higher when distension with the same volume of fluid was rapid than when distension was slow. This was seen most clearly when only short lengths of the intestine were distended. It is suggested that the effect is partly due to smooth muscle tone.3. Contraction of smooth muscle at the site of the receptor set up a discharge of impulses in the afferent fibre, and this response was not dependent on changes in intraluminal pressure. It was concluded that the receptors were tension‐signalling devices “in series” with the contractile elements in the smooth muscle.4. The receptors were unaffected by removal of the mucosa and submucosa, and probably lay in the muscularis externa of the stomach or intestines.5. The receptors were excited by intravenous injection of phenyl‐diguanide and adrenaline and by acetylcholine poured over the opened viscus. They were unaffected by 0·1N HCl. The difficulty of interpreting the action of ACh was pointed out.