[Mechanisms of the control of appetite]

The peripheral control of appetite is effected by two digestive hormones produced by the stomach and intestine. Bombesin, induced by gastric distension, might act as a messenger informing the nervous centres that the subject is satiated. The pharmacological satiating effect of cholecystokinin, probably mediated by the afferent fibres of the vagus nerve, is well established, but its physiological effect has not yet been demonstrated. Centrally, appetite is controlled by neurotransmitters, satiating and orexigenic properties being shared between monoamines, benzodiazepine-receptors and GABA-receptors. Among digestive hormones present in the central nervous system, the most satiating in pharmacological doses seem to be cholecystokinin and calcitonin, but their physiological role remains obscure. Insulin might be the signal informing the hypothalamus on body fat mass. Endorphins exert an orexigenic effect, reversed by naloxone, which is particularly marked in case of stress, in obese subjects and in the presence of highly palatable food. The control of appetite therefore is complex. It cannot be separated from other functions, such as pain and pleasure, which are regulated by intracerebral peptides.