Figure 8

Nissl-stained histologies (A and C) and adjacent autoradiograms (ARG's) at 20 min after ¹²⁵I-IGF-1 infusion (A and B, respectively; bregma -7.8 mm) and 90 min (C and D, respectively; bregma -6.8 mm). 8A. This section passes through the pineal gland, inferior colliculus (midbrain), aqueduct, and hippocampus and is just slightly caudal to Fig. 5C. Patches of small arteries and veins are scattered throughout the midbrain cisterns. 8B. The adjacent ARG shows some penetration of radioactivity into periaqueductal gray matter at 20 min and a minute amount within the midbrain cisterns. 8C. About 1.0 mm rostral to 7A, this section cuts through the superior colliculus, aqueduct, midbrain cisterns, dentate gyrus of the hippocampus, and the pontine nuclei (the large mass hanging below the midbrain). 8D. The matching ARG, obtained at 90 min, indicates considerable retention of ¹²⁵I-IGF-1 by the tissue immediately around the aqueduct and on both sides of the midbrain cisterns. The arteries and veins in the subarachnoid space also retain much radioactivity at this time. Scale bar = 1.5 mm.