Fig. 4. Immunohistochemical staining of NPR-A in eel brain counterstained with Haematoxylin (left) and corresponding cross-sectional planes (right). (A) Immunoreactive signal in capillaries of whole brain area as represented by the olfactory bulb (OB). (B) Immunoreactive neurons in reticular formation (RF), (C) glossopharyngeal-vagal motor complex (GVC), and (D) area postrema (AP) and commissural nucleus of Cajal (NCC) in the medulla oblongata. Approximate areas photographed are indicated by broken squares drawn in cross sectional planes. Regions indicated by arrowheads are magnified and shown in the boxed areas at the bottom of each photograph. Scale bar, 50 µm (magnified view, 30 µm). Locations of cross sectional planes are shown in Fig. 1. NSO, spino-occipital motor nucleus; IV, fourth ventricle.