1. The effect of
vagotomy on gastric acid secretion was studied in chronic
gastric fistula rats at various times after
denervation. In these rats basal and
pentagastrin-induced
acid output was permanently reduced. Thus, the magnitude of the
acid response to
pentagastrin in the conscious
fistula rat is dependent upon an intact vagus. 2. The
acid response to pylorus
ligation in vagally intact rats was unaffected by drainage of the stomach and therefore not caused by distension. Bilateral
vagotomy, performed simultaneously with the
ligation, completely abolished
acid secretion, while unilateral
vagotomy reduced the
acid output by half. Hence, in innervated rats, an intact vagal impulse flow appears to be essential for the
acid response to pylorus
ligation. When the pylorus
ligation was performed 2-8 weeks after
truncal vagotomy, the
acid output showed a progressive return towards pre-
denervation values. In the denervated rats the
acid response to pylorus
ligation was blocked by drainage of the stomach and therefore probably caused by distension, a mechanism which is independent of the vagal impulse flow. 3. The response to pylorus
ligation in innervated rats was blocked by
atropine and
chlorisondamine but not by
metiamide. In the denervated rats, the response to pylorus
ligation was blocked by all three drugs. 4. Following
ligation of both the pylorus and the oesophagus the
acid response was poor. With drainage of the oesophagus the
acid response was much enhanced, suggesting that oesophageal distension inhibits
acid secretion. In the vagotomized rat the poor
acid response to oesophageal + pyloric
ligation could not be overcome by drainage of the oesophagus. In the innervated rat gastric distension could overcome the inhibition induced by oesophageal
ligation. Also in chronically, but not in acutely vagotomized rats, gastric distension brought about a good
acid response. Conceivably, gastric reflex mechanisms can activate
acid secretion through vagal and/or intramural pathways. Both in innervated and denervated rats the response to gastric distension was inhibited by
atropine,
chlorisondamine and
metiamide. 5. The results suggest that in the innervated rat vago-vagal reflexes are important for the gastric hypersecretion following
ligation of the pylorus, and for the
acid response to gastric distension following
ligation of the pylorus and oesophagus. In the chronically vagotomized rat local intramural reflexes elicited by gastric distension are responsible for the
acid response.