Trigeminal reflexes and ingestive behavior in the rat.

Photographic, electrophysiological, and neurobehavioral analyses were used to examine the contribution of trigeminally mediated jaw-opening reflexes to the control of ingestive behavior in the rat. During eating and drinking, jaw opening was always preceded by a period of perioral contact with the food or water source. Stimulation (electrical, mechanical) of perioral areas in anesthetized animals elicited jaw-opening reflexes (recorded from the mylohyoid nerve trunk) at short latencies and low stimulus intensities. Trigeminal orosensory deafferentation (sparing jaw muscle afferents and efferents, taste, vision, and olfaction) abolished or significantly reduced mouth opening during eating or drinking. It is concluded that motivational processes operate through trigeminal reflexes to generate eating in the rat.