Receptor densities for angiotensin II and atriopeptin are particularly high in the dorsal vagal complex (DVC) of the caudal medulla oblongata. Measurements of glucose metabolism in individual components of the DVC, compared with those in Long-Evans rats, revealed that the area postrema was activated selectively both in water-sated and water-deprived Brattleboro rats, which have high circulating levels of angiotensin II. Other parts of the DVC, including subnuclei of the nucleus of the solitary tract and the dorsal motor nucleus of the vagus nerve, as well as brainstem structures within efferent trajectories of the DVC, had elevated rates of glucose metabolism in Brattleboro rats deprived of water overnight and in Sprague-Dawley rats dehydrated for 120 h. The findings are consistent with neural activation by angiotensin II, as either a hormone or neurotransmitter, within subregions of the dorsal medulla oblongata having high densities of putative receptors and immunoreactive perikarya and fibers containing both angiotensin II and atriopeptin.