Effects of food, glucose, and water ingestion on feeding activity in the toad (Bufo bufo).

Feeding in toads was tested by orient, approach, fixate, and snap responses to an artificial prey stimulus, before and at various times after feeding with natural prey (mealworms), or infusion of the gut with a prey-equivalent amount of glucose or volume of water. Feeding 5 prey objects or ad libitum feeding caused a decline in a prey catching when tested 2 hr later. Ingestion of 5 pulped mealworms or the equivalent glucose content and volume similarly decreased prey-catching, though an equal volume of water had no effect. Comparisons of the effect of time after glucose ingestion on prey-catching activity demonstrated that the major decline in activity occurred within 15 min, with no appreciable change after 2 hr. An equal volume of water had little effect on prey-catching activity over 15 min, but subsequent glucose ingestion reduced these behaviors. Thus, the decline in prey catching that occurs after feeding in toads can be rapidly replicated by ingestion of glucose, allowing future examination of the neural basis of satiety in these animals.