Trigeminal sensorimotor mechanisms and ingestive behavior.

Selective section of trigeminal orosensory nerves was carried out to assess the contributions of trigeminal orosensation to the control of food and water intake in the rat. Trigeminal orosensory deafferentation reduces a responsiveness to food and water, disrupts jaw-opening and tongue protrusion reflexes mediating eating and drinking, impairs dietary self-selection and reduces the level of long-term body weight regulation. The magnitude of the feeding behavior deficits is a joint function of the extent of the denervation and the sensory properties of the diet, and recovery takes place along a palatability gradient. Analysis of feeding and drinking patterns and of learned instrumental behaviors indicates that deafferentation reduces the probability of initiating a feeding or drinking bout and profoundly disrupts performance of operant responses reinforced with food or water. We conclude that the trigeminal system contributes to both the sensorimotor and motivational control of ingestive behavior. Its motivational contributions differ in both kind and magnitude from those of the gustatory system.