Vago-vagal reflex control circuits in the dorsal vagal complex of the brainstem provide overall coordination over digestive functions of the stomach, small intestine and pancreas. The neural components forming these reflex circuits are under significant descending neural control. By adjusting the excitability of the different components of the reflex, alterations in digestion control can be produced by the central nervous system. Additionally, the dorsal vagal complex is situated within a circumventricular region without an effective "blood-brain barrier". As a result, vago-vagal reflex circuitry is also exposed to humoral influences which profoundly alter digestive functions by acting directly on brainstem neurons. Behavioral and endocrine physiological observations suggest that this "humoral afferent pathway" may significantly alter the regulation of food intake.