Vagotomy abolishes the differential palatability of food.

The magnitude of preabsorptive insulin release varies as a function of palatability. This suggests that the palatability-dependent rise in plasma insulin could accentuate the systemic stimulus to eat, which in turn could modulate the size of the meal. The present experiment was designed to test this hypothesis by investigating the ingestive responses of vagotomized rats, which no longer exhibit preabsorptive insulin release, when they are offered nutritionally identical diets differing only in their sensory characteristics. The presented foods were three forms of the rat's regular diet: unaltered, sweetened with sodium cyclamate or adulterated with quinine hydrochloride. It was shown that vagotomized rats ate exactly the same amount of the three diets in three different test-meals: without cephalic insulin release, meal size no longer seems to be modulated by oral cues.