A permissive role for the vagus nerves in the genesis of antro-antral reflexes in the anaesthetized ferret.

1. The role of the vagus nerves in the genesis of antro-antral reflexes was investigated in the urethane-anaesthetized, splanchnectomized ferret. 2. Antral distension stimulated antral contractions with a threshold volume of 3.5 +/- 0.9 ml (corresponding to an intra-antral pressure of 0.27 +/- 0.11 kPa) by a vagal-dependent mechanism as indicated by the attenuated response seen during vagal blockade by cooling. Atropine (1 mg/kg) abolished the antral response to distension. 3. In vagotomized animals, close arterial infusions of acetylcholine at a dose sufficient to return antral motility to basal levels led to the reappearance of the reflex. Low-frequency electrical stimulation of the preganglionic vagal neurones had a similar effect. These effects were also abolished by atropine (1 mg/kg). 4. Hexamethonium (10-25 mg/kg) suppressed the potentiating effect of acetylcholine, indicating a ganglionic site of action. The attenuated response to antral distension seen in vagotomized animals in the absence of exogenous acetylcholine or electrical vagal stimulation was not sensitive to hexamethonium but abolished by atropine (1 mg/kg). 5. The results are consistent with the vagus performing a permissive role in the genesis of antro-antral reflexes mediated through local enteric pathways.