FIGURE 7.

mGluR5 immunohistochemical expression in human hippocampal formation: Ammon∼s horn, subicular complex, and entorhinal cortex. In HS CA4 (A, left), mGluR5 was upregulated in pyramidal neurons. In control CA4 (A, right) mGluR5 staining was light and predominant in the neuropil. HS CA3 (B) staining pattern exhibited few immunopositive fibers and neurons. On the other hand, HS CA2 (C, left) showed densely stained pyramidal neurons and packed tortuous dendrites in the radiatum-lacunosum. Arrowheads in CA2 point to interneurons. Non-HS CA2 (C, right) exhibited dense neuropil staining with visible long and organized dendrites, a typical pattern in all non-HS Ammon∼s horn subfields. In the stratum oriens margin between CA2 and CA1, interneurons were also strongly mGluR5 positive in HS cases (D, left), but not in non-HS (D, right). In the Sommer∼s sector, HS CA1 (E, left) and prosubiculum (F) exhibited mGluR5 staining in the few remaining neurons (asterisks) and a mesh of strongly mGluR5 positive fibers. Subiculum (G) showed dense immunostaining in the neuropil and in transverse neuronal fibers. The cytoplasm of pyramidal cells was less strong IR than the neuropil. Nuclei and blood vessels were devoid of immunoreactivity. A similar pattern was observed in the islands of parasubiculum (H) and in the presubiculum (I), where primary dendrites showed distinctive strong IR. A similar staining pattern was found in non-HS cases. The entorhinal cortex (J) also displayed marked neuropil staining (J, left), which was also a feature of non-HS cases. In HS, EC layer II clusters of neurons (J, right) from where perforant path fibers arise were especially stained. In the white matter enclosed between the subiculum and the entorhinal cortex (K, left), numerous fibers of probable glial and axonal origin were positively stained. Such fibers seem to emerge from the entorhinal cortex in direction to the subicular complex and hippocampus (J and K, excerpts). Strong mGluR5 immunoreactivity was also found in interstitial white matter neurons (K right, hash signs). Such profiles were not distinguishable in non-HS or in control hippocampal formation. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]