The arcuate nucleus as a circumventricular organ in the mouse

The present study searched for morphological correlates of the permeability of the ventromedial arcuate nucleus of the mouse to blood-borne proteins. First, we determined that highly permeable microvessels are detected in the ventromedial arcuate nucleus using a rat monoclonal antibody to a mouse-specific endothelial phenotype (clone MECA32) recently recognized as a marker of endothelial fenestral diaphragms and previously shown to label circumventricular organs. Second, in the mild conditions of tissue fixation mandatory for use of MECA32, we observed that after a rapid vascular flush with saline, endogenous immunoglobulins are especially retained in circumventricular organs and ventromedial arcuate nucleus. The ventromedial arcuate nucleus thus shares features in common with classical circumventricular organs. (C) 2010 Elsevier Ireland Ltd. All rights reserved.