Vagal afferent integration of meal-related GI signals in rat

The vagus nerve is the primary neural link between gut sites that process ingested nutrients and central nervous system sites underlying the control of food intake. Vagal afferent fibers supplying the GI tract respond to both chemical and physical properties of ingested foods. Since ingested food may provide simultaneous chemical, peptide-induced and mechanical stimulation at multiple GI sites, we investigated the possibility that a single vagal afferent had the potential to integrate signals arising from multiple stimuli. Two types of integration have been identified. One type, polymodal integration, occurs where peptidergic stimulation potentiates and synergizes with the vagal afferent neurophysiological response to mechanical stimulation of a single gastrointestinal compartment. The second type, polytopic integration, occurs where stimulation of one gastrointestinal site modifies the single vagal afferent response to stimulation of a different gastrointestinal compartment. Both types of vagal afferent integration may underlie the control of food intake. (Supported by NIDDK 19302 and the Whitehall Foundation.).