Figure 1

Nissl-stained histologies (A and C) and adjacent autoradiograms (ARG's; B and D) showing the lateral (LV) and the third (3 V) ventricles 30 min after injection into one lateral ventricle (A and B, respectively) or into the parenchyma (C and D, respectively). 1A. This histological section is at bregma -0.2 mm and cuts through the cerebral cortex (not labeled), LV, caudate-putamen (CPU), 3 V, anterior commissure (not labeled), and the optic chiasm (missing on the histology, but evident on the ARG, 1B). 1B. The lateral ventricle choroid plexus and the walls of the LV and 3 V on the ipsilateral side are darkly labeled on this ARG, but little radioactivity is evident in the ventricles. The flattened loop of moderate darkness at the very bottom of the ARG demarcates the subarachnoid space around the optic chiasm. The dark half-ring or crescent above the optic chiasm partially surrounds the medial nucleus of the preoptic area, a peculiar pre-hypothalamic structure; this crescent appears to be an extension of the ventral part of the 3 V but may be an artifact. 1C. This section is at bregma -0.3 mm and passes through the same structures as 1A above. Notable on this histology are the needle tract and corpus callosum, which on the ipsilateral side below the tract is expanded, pale, and edematous. 1D. Most of the radioactivity in this ARG is contained in the tissue near the main site of the intraparenchymal infusion, but some is in the choroid plexus and CSF (both shown by the tail below the main patch of blackness on the ARG). Much of the tissue radioactivity is in the corpus callosum and some of it extends via this white matter tract across the midline. Scale bar = 1.5 mm.