EFFECTS OF ANESTHETIC AGENTS ON BASAL AND HISTAMINE-STIMULATED ACID-SECRETION IN THE FISTULA RAT

Objectives: Anaesthetized rats or surgically modified preparations suc h as the Shay rat are widely used to study upper gastrointestinal func tion in the laboratory. Despite the existence of reports demonstrating that agents such as barbiturates can influence acid output, a systema tic study of the effects of anaesthetics on gastric secretion has not been undertaken. Methods: Basal and histamine-stimulated acid output w ere measured in chronic fistula rats after administration of injectabl e and volatile anaesthetics frequently used in studies of gastric secr etion in anaesthetized animals. With the exception of ether, for which recovery is very rapid, sedating rather than full anaesthetic doses w ere used. Results: Chloralose (40 mg/kg) had no significant effect on gastric secretion. Pentobarbitone (25 mg/kg) inhibited basal and hista mine-stimulated acid output, but the effect was relatively short-lived and secretion returned to control levels after 2 h. Urethane (750 mg/ kg) markedly inhibited basal acid output and abolished the secretory r esponse to histamine given 15 to 60 min later. The effects of urethane on acid secretion persisted for the entire 3 h duration of experiment s, during which time basal acid output declined to levels observed in fully anaesthetized rats given 1.5 g/kg. Full anaesthesia with ether f or 60 min also caused profound inhibition of basal secretion and, like urethane, abolished the effect of histamine despite the fact that the animals recovered consciousness within 5 min. Conclusions: The differ ential activity of anaesthetics and profound antisecretory activity of ether and urethane should be taken into account when studying gastroi ntestinal function and mucosal ulceration in anaesthetized animals.