Deductive functional assignment of elements in appetite regulation.

This paper presents a simple mathematical model for energy transport from the body into the brain and for appetite regulation. Particular properties in appetite regulation are deduced from the general observation of cyclic food intake. These particular properties are the importance of a push component, however small it may be, from the body into the brain, the dependence of the appetite activation on the energy supply level in the brain and a necessary condition for the sensitivity of this dependence. The dominant pull component in the energy transport is accompanied by a smaller push component managing this information transport. The properties listed above correspond to physiological observations. For instance, sensitivity is found in the postnatal development of projections between neuropeptide Y (NPY) neurons and pro-opiomelanocortin (POMC) neurons, which release, respectively, the appetite-amplifying and -reducing neuropeptides NPY and alpha-melanocyte-stimulating hormone at their nerve terminals. The development of these projections determines the change from the permanent feeding of the foetus into the cyclic ingestive behaviour in later life. The correspondence verifies the mathematically-deduced properties, justifies the simple model and supports the technique of the deductive functional assignment.