Fig. 5.

Adult rats subjected to thymectomy at birth recover poorly from CNS injury. Thymectomized rats (n = 18) were subjected to a partial crush injury of their optic nerves. One week before the optic nerve crush, 8 of these rats underwent spinal cord contusion (precontused ON crush; thymectomized) and 10 underwent a sham operation (ON crush; thymectomized). Two weeks after optic nerve injury the surviving neurons were labeled, and 5 d later the retinas were excised and their RGCs counted. Normal rats (n = 9) were subjected to optic nerve crush only (ON crush). The number of RGCs per square millimeter in each animal is shown. Thymectomy had a significant effect on RGC survival, both in the absence of previous contusion (p < 0.003) and in the precontused group (p < 0.01; t test).