Water drinking induced by gastric secretagogues in pigs

Eleven young pigs, feeding and drinking operantly, were tested for drinking responses to three gastric secretagogues. First, feed was removed for 1 h before the test period, then a continuous intravenous infusion of saline or a secretagogue was begun at a priming rate of 0.6 ml/min for the first 10 min, then at 0.3 ml/min for 50 min. Dose rates were the smallest that would still cause a vigorous gastric secretion. When 0.9% NaCl was infused, the pigs drank a mean of 54 +/- 11 (SE) ml. The comparable volumes for the secretagogues were histamine 174 +/- 41 ml (1 microgram . kg-1 . min-1); pentagastrin 231 +/- 38 ml (0.5 microgram . kg-1 . min-1); and bethanechol 231 +/- 35 ml (1.0-1.5 microgram . kg-1 . min-1). Pretreatment with cimetidine (300 mg iv) depressed the drinking response to histamine to 30 +/- 10 ml and to pentagastrin to 58 +/- 24 ml. Atropine (2 mg iv) depressed the response to bethanechol to 28 +/- 16 ml. Differences between responses to the secretagogues and either control drinking or antagonist-blocked responses were all significant (P less than 0.001). The results indicate that gastric secretion could play a role in stimulation of preprandial water drinking.