Central structures involved in opioid-induced feeding.

This paper summarizes efforts to identify structures involved in the opioid regulation of feeding. Many opioid agonists and antagonists increase or decrease food intake when injected centrally, which suggests, but alone does not prove, that the opioid feeding system is located within the brain. Some conditions of hunger and feeding cause changes in opioid peptide levels in certain brain areas, notably the hypothalamus, which may indicate that the areas are components of this opioid system. Lesion studies have also identified some potentially important structures, inasmuch as lesions of these structures reduce the effectiveness of opioid agonists or antagonists to alter food intake. Finally, microinjection studies have mapped the brain in terms of the effects on feeding of opioid agonists and antagonists. Results of different types of studies are consistent in suggesting that parts of the hypothalamus, particularly the paraventricular and ventromedial nuclei and the lateral hypothalamic area, are important components of the opioid feeding system.