Cerebral T2-weighted signal decrease during aging in the mouse lemur primate reflects iron accumulation.

4.7 Tesla T2-weighted magnetic resonance images showed a highly significant signal decrease in the pallidum, substantia nigra, putamen, and a less significant decrease in the thalamus and the caudate of aging mouse lemurs (Microcebus murinus). We evaluated the contribution of iron deposits to the signal decrease comparing Perls' stained histological sections of six mouse lemurs brains aged 1 to 10 years to magnetic resonance images. In young animals, none of the brain structures was stained. A large number of iron deposits were visible in the pallidum and substantia nigra of aged animals and a moderate number in the middle aged ones. In the putamen, few iron deposits were visible in aged and middle-aged animals. The thalamus and the caudate appeared unstained with Perls' technique; iron was too low to be detected. The intensification of the reaction by diaminobenzidine revealed iron deposits in the thalamus of aging animals. This study suggests that in mouse lemurs, iron deposits are responsible for T2-weighted signal decrease in the central gray nuclei.