Figure 7

Distribution of ¹²⁵I-IGF-1 radioactivity in five CSF compartments as a function of time after ending the infusion. The data are shown as mean ± SD at the various times. The first two sets of points are at 5 and 9 min. By 5 min, the peak concentrations have already passed through the lateral and third ventricles and the aqueduct; at 30 min, ¹²⁵I-IGF-1 in these three compartments has fallen to <750 nCi/g. Radioactivity in the fourth ventricle reached a plateau over the 9–20 min period and dropped thereafter. In the midbrain cisterns, ¹²⁵I-IGF-1 sharply rose from 20 to 45 min and then fell continuously thereafter. The peak radioactivity at 45 min is notable, exceeding that in the 4^th ventricle by 5-fold. These curves show that ¹²⁵I-IGF-1 moved relatively briskly through the ventricular system.