Neuroendocrine Integration of Body Weight Regulation

This chapter attempts to provide an overview of the known physiological processes that occur in the brain to integrate and analyze a large variety of afferent signals reflecting energy requirements and that respond with the appropriate compensatory changes in appetite, metabolism and behavior. Immediate conditions instantly induce hormonal and neuronal messages from the periphery that communicate to distinct areas of the brain the need for regulatory changes in order to maintain energy balance. It is within these brain areas that not only sensations such as hunger and satiety are created, but also outgoing impulses for food seeking behavior, changes in locomotor activity or appropriate modulations of peripheral metabolic drive are triggered. The localization and precise action of these brain centers, as well as the exact mapping of their interactive signal transduction pathways, remain largely unknown despite great scientific progress in this field during the last two decade. A finely tuned balance of action potentials, synaptic neurotransmitters, feedback loops and neuropeptide expression levels between regulatory centers in the brainstem, hypothalamic nuclei, basal ganglia, nucleus accumbens and even the cortex underlies the constant adjustments that take place. The redundant multiplicity of factors governing energy balance, that have been generated due to the evolutionary need to ensure sufficient caloric intake, is regarded as one reason for the continued failure to generate an effective pharmacotherapy for obesity.