Postingestive factors influencing operant sugar intake in pigs

Intravenous injections of glucose, which increased plasma glucose levels to approximately 10 times the normal level, had no significant effects on the amount of glucose consumed in operant tests carried out immediately after the injection. The importance of gastrointestinal factors in regulating glucose intake was demonstrated in experiments in which pigs with gastric cannulae sham drank significantly (p < 0.01) more glucose over a 1-h period than control sessions with the cannula closed. Intraduodenal injection of glucose or mannitol significantly reduced glucose intake, with glucose significantly (p < 0.05) more effective than mannitol and both significantly (p < 0.01) more effective than water. Gastrointestinal factors are important in regulating sugar intake whereas blood sugar levels are not. The pig is a good experimental animal for the study of sugar appetite.