Microphotographs showing the distribution of Zonula occludens-1 (ZO-1) and vimentin immunoreactivities in coronal sections of the tuberal region of the hypothalamus. Images were acquired either at low (B) or high (A, C, D–G) magnifications. ZO-1 (green) immunoreactivity is readily visualized in capillaries of the cerebral parenchyma, which are known to display well-differentiated tight junction complexes (A). ZO-1-immunoreactivity is also evident at the wall of the third ventricle (B). Notably, ZO-1 immunostaining displays a honeycomb distribution in cuboidal ependymal cells (C). Ventral to the DMH, where the tanycytes appear, the honeycomb ZO-1-immunoreactive pattern gradually disappears and is replaced by an unorganized staining pattern (D). This unorganized distribution of ZO-1-immunoreactivity becomes obvious in the tanycytes of the ARH (E). In contrast, tanycytes of the median eminence exhibit a honeycomb pattern of ZO-1 expression (F,G). Sections are counterstained using Hoechst (blue) to visualize cell nuclei and recognize the morphological limits of each hypothalamic structure. 3V, third ventricle; ARH, arcuate nucleus of the hypothalamus; DMH, dorsomedial nucleus of the hypothalamus; VMH, ventromedial nucleus of the hypothalamus. Scale bar = 100μm in B; 20μm in G.