Figure 1.
MRI evaluation of the effect of streptozotocin at 1 and 3 mg/kg in rats one week and three months following icv injection.
A. A dilation of the ventricle (white signal on MRI, yellow arrows), an atrophy of white matter (red arrows) and septal alterations are visible after icv-streptozotocin. They are obvious in the 3 mg/kg treated animals. B. Quantification of the septal volumes showing an atrophy process in both treated groups. C. Thickness of the corpus callosum in controls, 1 mg/kg and 3 mg/kg treated-animals before the streptozotocin administration, one week and three months post-injection. D. Quantification of the striatal volumes showing no atrophy whatever the groups. Examples of the regions of interest used to outline the septum and striatum are showed in B and D, respectively. Values are mean±SEM. *: p<0.05; **: p<0.01; ***: p<0.005. S: Septum. Cpu: Striatum.
Figure 2.
Evaluation of neuronal density on NeuN stained sections after icv- streptozotocin.
A. Histological sections showing the septum (S), striatum (Cpu) and lateral ventricles (LV) in the control, 1 mg/kg and 3 mg/kg streptozotocin-treated animals, one week and three months post injection. Dilation of ventricles and septal alterations are visible in the 3 mg/kg-treated group (arrows). B. Septal neurons density started to decrease one week post injection in the 3 mg/kg group but not in the 1 mg/kg animals. This septal neuronal alteration worsened with time and was highlighted in 1 mg/kg and 3 mg/kg streptozotocin-treated animals three months following the administration of the toxic. C. No modifications of the striatal NeuN labeling density were highlighted one week or three months post injection in control group and in both streptozotocin-treated group. Values are mean±SEM. *: p<0.05; ***: p<0.005. Scale bars = 2 mm.
Figure 3.
Evaluation of DARPP-32 positive regions.
DARPP-32 positive striatal volumes were not modified in all groups three months following the injection (Mann-Whitney U Test, NS). Values are mean±SEM. Scale bars = 2 mm.
Figure 4.
Evaluation of the astrogliosis in control (A, G), 1 mg/kg (B, H) and 3 mg/kg (C, I) icv-streptozotocin treated groups, seven days (A–C) and three months (G–I) post injection.
MRI sections corresponding to the histological sections are shown in D–F (one week post- injection) and J–L (three months post-injection). Low and high (left insets) magnification images showing Glial Fibrillary Acidic Protein (GFAP) staining. A severe astrogliosis was detected in the 3 mg/kg treated group (halo of activated astrocytes in C (arrow), insets in C and I). A slight astrogliosis could be detected in the 1 mg/kg animals (B, H). The inflammation process was not obvious on MR images at both times and in all groups (D–F for one week post-injection, and J–L for three months post-injection). However, dilation of the ventricles was clearly visible on these same images in STZ-treated-animals. S: Septum. Cpu: Striatum. Scale bars for low magnification images = 2 mm and scale bars for insets = 50 µm.
Figure 5.
Evaluation of the microgliosis in control (A, D), 1 mg/kg (B, E) and 3 mg/kg (C, F) icv-streptozotocin treated groups, seven days (A–C) and three months (D–F) post injection.
Pictures show Iba-1 staining (microgliosis). A severe microgliosis was detected in the 3 mg/kg treated group in the regions adjacent to the lateral ventricles (C and F). In the 1 mg/kg group, this microglial activation was less severe at both time points (B and E). Other brain regions did not display abnormal hyperactivated gliosis. Scale bars = 50 µm.