Vagovagal reflex control of digestion: afferent modulation by neural and "endoneurocrine" factors.

Vagovagal reflex control circuits in the dorsal vagal complex of the brain stem provide overall coordination of gastric, small intestinal, and pancreatic digestive functions. The neural components forming these reflex circuits are under substantial descending neural control. By adjusting the excitability of the differing components of the reflex, significant alterations in digestion control can be produced by the central nervous system. Additionally, the dorsal vagal complex is situated within a circumventricular region without a "blood-brain barrier." As a result, vagovagal reflex circuitry is also exposed to humoral influences, which can profoundly alter digestive functions by acting directly on brain stem neurons.