Glucose sham drinking in the rat: satiety for the sweet taste without the sweet taste.

In rats sham drinking through oesophageal fistulae, sham intake of a dilute glucose solution (0.25 M) is greatly reduced, but not abolished, by an intragastric water preload. Since no further fluid enters the body, the early cessation of sham drinking must reflect a purely oral control, set by hydrational status. We show that lapping after the water load is abolished if the rat has sham-drunk appreciable quantities before the load is delivered. This is true even if the initial sham drinking is of plain water, with no sweet taste. Therefore, (1) the effect of the preload is to set the total quantity of oral feedback required to end the sham drinking bout; and (2) the necessary oral feedback is provided by the lapping response itself. It does not depend upon gustation.