Central nervous system control of food

Schwartz MW, Woods SC, Porte D Jr et al (2000) Central nervous system control of food intake. Nature 404 661-671... 

The gut contains a collection of nerves called the enteric nervous system. Various activities of the gut, such as peristaltic contractions, and certain activities of the pancreas and gall bladder, are controlled in a manner that is relatively independent of the central nervous system. The central nervous system consists of the brain and spinal cord. Five type,s of activity are controlled by the enteric nervous system (1) contraction of smooth muscles that create the peristaltic waves used to mix and propel food through the intestines (2) release of juices by secretory cells (5) release of hormones from endocrine ceils of the gut (4) patterns of blood flow through the arteries of the gut (variations in blood flow occur because of the opening of blood vessels (vasodilation) or the dosing of blood vessels (vasoconstriction)] and (5) activities of immune cells of the gut (GoyaI and Hirano, 1996). 

In sum, the control of food intake and body weight is extraordinarily complex and not fully understood. On top of a multigenic control background, we have layered on a family of adipose and gut hormones that act through the central nervous system in the context, in the United States at least, of an enviromnent laden with an abundance of calorie-dense, nutrient-poor foods. 

Agazzi, M.F .., Moreno, J.B., von Holst, C., Lucker, E., and Anklam, E. 2004. Quantitative analysis of tissues of the central nervous system in food products by GFAP-ELISA test kit. Results of an interlaboratory study. Food Control 15, 297-301. 

The serotonergic neuronal system is one of the most extensive in the central nervous system. The cell bodies of this system are clustered in approximately 10 groups known as Raphe nuclei in the midbrain and lower brain stem. Nevertheless, the axons and terminals permeate every major brain region and the neurons functionally subserve a variety of physiologic functions, including food and water intake, sexual activity, sleep thermoregulation, regressiveness, and blood pressure control. 

Control of food intake is certainly one of the functions of leptin — reduced food intake can be observed in response to direct injection of the peptide into the central nervous system, and in response to leptin there is increased secretion of a number of peptide neurotransmitters that are known to be involved in regulation of feeding behaviour. However, the weight loss seen in response to leptin is greater than can be accounted for by the reduced food intake alone. Furthermore, in response to leptin there is a specific loss of adipose tissue, whereas, as discussed in section 8.2, in response to reduced food intake there is a loss of both adipose tissue and lean tissue. 

As to be expected from a peptide that has been highly conserved during evolution, NPY has many effects, e.g. in the central and peripheral nervous system, in the cardiovascular, metabolic and reproductive system. Central effects include a potent stimulation of food intake and appetite control [2], anxiolytic effects, anti-seizure activity and various forms of neuroendocrine modulation. In the central and peripheral nervous system NPY receptors (mostly Y2 subtype) mediate prejunctional inhibition of neurotransmitter release. In the periphery NPY is a potent direct vasoconstrictor, and it potentiates vasoconstriction by other agents (mostly via Yi receptors) despite reductions of renal blood flow, NPY enhances diuresis and natriuresis. NPY can inhibit pancreatic insulin release and inhibit lipolysis in adipocytes. It also can regulate gut motility and gastrointestinal and renal epithelial secretion. 

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