Fig. 1

Latexin staining of the rat claustrum in four planes of section. a Coronal section at a plane approximately 1 mm caudal to bregma [57, 58]. The densely latexin-stained, “egg-shaped,” principal subregion of claustrum is located in the same horizontal plane as the rhinal fissure. The latexin-negative medial core of endopiriform nucleus and its crescent-shaped latexin-positive shell are visible ventral to the densely-stained “egg-shaped” region of claustrum. A latexin-positive, but less densely-stained group of cells extend dorsally and border a latexin-negative region located medially. These two subregions are also debatably part of claustrum, but our study concentrates on the “egg-shaped” subregion that appears in every definition of claustrum. b Horizontal section at a plane approximately 6.6 mm below bregma. The principal claustral subregion is evident at about 1/3 of the distance from the top of the figure, but sparser staining rostrally (endopiriform nucleus and caudally (claustral cells dorsal to the densest staining) are evident. c Sagittal section at a plane approximately 4.6 mm lateral to the midline highlights the densely-stained claustrum. d An oblique section that optimizes capture of latexin-positive claustral cell dendrites. This section was cut at 30° off the horizontal in a rostro-dorsal to caudo-vental direction. Scale bars 1 mm