Vagal afferent discharge from mechanoreceptors in different regions of the ferret stomach.

1. The rate and volume of gastric filling was estimated in conscious ferrets by measuring the amount of milk they would drink after an overnight fast. The mean volume was 94.5 +/- 7.5 ml. at a rate of 13.0 +/- 0.74 ml./min. An intragastric infusion rate of 10 ml./min to a total of 50 ml. was selected as a standard distension stimulus. 2. Action potentials were recorded from single gastric afferent fibres in the cervical vagus. All but two of thirty-six afferent units were tonically active when the stomach was deflated. 3. Afferent fibres arising from receptors in the antrum showed modulation in phase with spontaneously occurring antral contractions. Afferent fibres from the corpus and fundus, however, discharged at irregular rates between 0.35 and 7.5 Hz with no correlation with the intragastric pressure rises associated with the antral contractions. 4. Inflation of the stomach with 50 ml. 0.9% NaCl at a rate of 10 ml./min stimulated antral motility and the rhythmic afferent discharge from the antrum was enhanced Receptors in the corpus and fundus increased their rate of discharge with increasing gastric volumes. Receptors in the region between the antrum and the corpus had the property of both types so that they responded to both distension and contractions. 5. On distension with 0.9% NaCl, fluid is distributed unevenly in the stomach. 80% was accommodated in the corpus and fundus, the remainder of the fluid entering the antrum. 6. The tension was measured in strips of stomach wall taken from corpus and antrum. For equal increments of stretch the development of tension was greater in the antral than in corpus strips. This physical property together with neurally mediated receptive relaxation of the corpus is the reason for the fluid distribution described above. 7. It is concluded that the properties of the tension receptor are determined by their site in the stomach. Those in the body and fundus signal the degree of distension and those in the antrum signal information concerning the amplitude, rate and duration of antral contractions.