Sensory circumventricular organs and brain homeostatic pathways

Circumventricular organs (CVOs), small structures bordering the ventricular spaces in the midline of the brain, have common morphological and endocrine-like characteristics that distinguish them from the rest of the nervous system. Among their unique features are cellular contacts with two fluid phases--blood and cerebrospinal fluid--and neural connections with strategic nuclei establishing circuitry for communications throughout the neuraxis. A variety of additional morphological and functional characteristics of the CVOs implicates this group of structures in a wide array of homeostatic processes. For three of the circumventricular organs--the subfornical organ (SFO), the organum vasculosum of the lamina terminalis (OVLT), and the area postrema (AP)--recent findings demonstrate these structures as targets for blood-borne information reaching the brain. We propose that these three sensory…