Cellular localization of the blood-brain barrier in the brainstem: Area postrema and nucleus tractus solitarius

Abstract: The blood-brain barrier regulates the transport into the brain and protects the central nerve system (CNS) from toxics substances. However some areas of the brain, called circumventricular organs (CVO), lack the blood-brain barrier. One of these is area postrema (AP), which is located in the brainstem immediately adjacent to the nucleus tractus solitarius (NTS). These two areas together regulate autonomic behaviours such as food intake, and also make up the vomiting center. The hormones leptin and ghrelin, which regulate food intake, are too big to pass the blood-brain barrier, but have receptors in NTS. In this study we used immunohistochemistry to obtain a detailed map of the different components of the blood-brain barrier in AP and NTS. The results suggest that there is a barrier that prevents diffusion of substances from AP into NTS. However, there seems to be some vessels in NTS that have a weaker or no barrier characteristics. These vessels could provide an entrance for peripheral substances to neurons in NTS.