Hyperosmotic stimulus increases VEGF expression within SON neurons. A-B: Immunostaining for VEGF in control (A) and 6 days osmotically stimulated adult rats (B). Stack confocal images (10 μm-thick) of SON neurons show that moderate VEGF immunostaining is localized to perinuclear, golgi-like structures in the control rat (A), whereas intense immunostaining is dispersed throughout the cytoplasm in the stimulated rat (B) (insets show higher magnification of immunostained neurons). C-D: In situ hybridization for VEGF mRNA in control (C) and 6 days osmotically stimulated adult rats (D). Light microscope micrographs of 20 μm-thick cryostat sections showing that the mRNA labeling detected within the SON is highly increased in the stimulated (D) as compared with the control (C) rat. OC: optic chiasma; VEGF: vascular endothelial growth factor. Scale bars: A-B = 100 μm; C-D = 100 μm; insets = 50 μm.