Vagal control of transpyloric flow and pyloric resistance.

Vagal control of pyloric resistance was evaluated in anesthetised pigs by recording gastropyloroduodenal motility and transpyloric flow during emptying of a liquid nonnutrient meal. Vagotomy did not modify pyloric resistance or the characteristics of the flow pulses. Electrical stimulation of the distal stumps of cervical or thoracic vagus nerves decreased pyloric resistance and triggered flow pulses of large stroke volume. This was associated with increased fundic tone and pressurization of the antrum. Phentolamine but not propranolol reduced the responses to vagal stimulation. These observations demonstrate that reduced pyloric resistance is one mechanism by which vagal activation promotes transpyloric flow.