Role of vagal and splanchnic nerves for gastric motility changes in response to chemical stimulation of canine gastric mucosa.

The reflex control of gastric motility induced by chemical stimulation to a canine gastric mucosa was electromyographically studied in anesthetized dogs. In splanchnicectomized dogs, the instillation of 5 ml of HCl solution with various pHs (pH 1-4) evoked a decrease in electrical control activity (ECA) frequency in accordance with stimulus strength. These responses were abolished by cervical or thoracic vagotomy. These results indicate that both afferent and efferent limbs of the reflex are in the vagus nerves. The results of alkaline stimulation was different from those of acidic stimulation. Decreasing response of ECA frequency following alkaline stimulation was completely abolished after the vagotomy similar to the acidic stimulation. On the other hand, the duration of the decreasing response to alkaline stimulation recovered faster than the response to acidic stimulation in the splanchnicectomized dogs. These results indicate that splanchnic nerves are contributing to the long lasting response to alkaline stimulation but not to that in acidic stimulation. The present experiment shows that the ECA frequency decreased after the acidic stimulation. When the stomach was filled with foods, the gastric pH may lower. Thus, decrease in ECA frequency after the acidic stimulation seems to play a physiological role of gastric contraction after feeding.