Fig. 6. The initiation of hydrocephalus precedes aqueduct stenosis in Tg737^orpk mutant mice. Movement of DiI (red) was tracked through brain sections of 2- and 6-day-old wild-type and Tg737^orpk mutant mice, 10 minutes post-injection. (A,B) Horizontal view of brains showing the lateral ventricles (black arrows), third ventricle (black arrowheads) and fourth ventricle (white arrowheads). (C-H) Fluorescence images of brain sections through the indicated regions from (C,E,G) 2-day-old and (D,F,H) 6-day-old control and mutant mice. DiI is detectable in the fourth ventricle of 2-day-old mutants (A,G, right panels), but is not seen in 6-day-old mutants (B,H, right panels), indicating that CSF movement was obstructed in these mutants. Scale bar: 200 µm.