Figure 5

Immunohistochemistry of aquaporin-4 in the periventricular region. A: low magnification picture representing a control rat. The boxed area shows the studied periventricular region. B and C: different patterns of aquaporin-4 immunoreactivity. Aquaporin-4 positive glial processes were identified as reticular pattern and perivascular "vessel-like" structures. "Vessel-like" immunoreactivity was identified either as strongly labeled round/eliptical structures where we expect a vessel is cut across (B, arrow) or as parallel lines with branches where a vessel is cut in its length direction (C, arrow). "Vessel-like" immunoractivity was identified in all cases. The reticular pattern could further be categorized as either continuous (B) or discontinuous (C). In cases of discontinuous reticular pattern, larger areas were found devoid of the reticular pattern. In controls the continuous pattern prevailed, in the acute phase (two day and one week) a trend pointed towards the discontinuous pattern, and finally at 2 weeks the reticular pattern was again prominent. The inserted table summarizes the proportion of rats in each group presenting either continuous or discontinuous reticular pattern and the proportion of rats showing perivascular "vessel-like" immunoreactivity. This suggests a dynamic response in the expression pattern of aquaporin-4. No evidence of immunoreactivity in cell soma of astrocytes was found. Negative immunohistochemistry controls did not show any immunoreactivity. * = lateral ventricle. A scale bar 100 μm; B and C scale bar 50 μm.