[Central neurotransmitters and control of specific appetite for the macronutrients]

Studies of brain monoamines and neuropeptides have provided extensive evidence in support of their role in the control of food intake, meal patterns and appetite for specific macronutrients. In this process, the medial and lateral portions of the hypothalamus have a critical responsibility in balancing signals for hunger and satiety. Via its rich and biologically active neurotransmitter substances, the hypothalamus monitors and integrates the complex sensory and metabolic input concerning the nutritional status of the organism and transduces this information into appropriate quantitative and qualitative adjustments in food intake. The specific neurotransmitters for which there is the most extensive evidence for a physiological function include the eating-stimulatory substances norepinephrine, opioid peptides, pancreatic polypeptides, galanin and gamma-aminobutyric acid; and the eating-inhibitory substances dopamine, epinephrine, serotonin and several gut-brain peptides. From biochemical, pharmacological and anatomical studies, hypotheses have been generated to explain the role of these various monoamines and neuropeptides in controlling total energy intake, in determining the amount and pattern of macronutrient selection, and in maintaining normal energy and nutrient stores under dynamic conditions within the external environment.