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. 2000 Apr 1;20(7):2439–2450. doi: 10.1523/JNEUROSCI.20-07-02439.2000

Fig. 5.

Fig. 5.

Heterotopic somatostatin- and parvalbumin-containing interneurons in the Lis1+/−hippocampus. Immunohistochemical techniques were used to determine the expression pattern of markers specific for inhibitory interneuron populations. A1, A2, In wild-type hippocampus, parvalbumin (PV) is found in interneurons whose somata are located primarily in the stratum pyramidale and stratum oriens. A2 illustrates a higher magnification of the boxed region in A1. The somatodendritic profile of these cells is generally perpendicular to the principal cell layer. The axons of PV interneurons are largely confined to stratum pyramidale and form a dense plexus around the somata of pyramidal cells. B1, B2, The distribution of PV-containing interneurons in Lis1+/−sections closely resembled those found in wild type. Somas maintained their associations with the stratum oriens and stratum pyramidale layers, whereas their axonal processes remained in stratum pyramidale. Consequently, PV-containing interneurons appeared in multiple bands caused by the disorganization of the Lis1+/−stratum pyramidale. B2 illustrates theboxed region in B1 at a higher magnification. Note that PV-positive cell bodies are found in both heterotopic principal cell layers. All immunostained sections have been Nissl-counterstained to allow visualization of the inhibitory interneurons relative to the heterotopic principal cell layers.C1, C2, In wild-type hippocampus, somatostatin (SOM)-containing interneurons were predominantly found in CA1 stratum oriens-alveus. The CA3 subfield contains a broader distribution of SOM interneurons with somas found in stratum pyramidale, stratum lucidum, and stratum radiatum. The hilar region of the dentate gyrus also contained numerous SOM-positive interneurons. C2, Higher magnification of the boxed region indicated that C1 shows typical somatostatin-containing cells of the CA1 stratum oriens. These cells typically possess horizontally oriented somata and dendrites.D1, D2, In the CA1 subfield of theLis1+/− hippocampus (5×, 25×), numerous SOM-containing interneurons were observed not only in the stratum oriens but were dispersed throughout the clusters of CA1 pyramids and deep within the stratum radiatum areas (the boxed region in D1 is shown at high magnification inD2). In this particular hippocampus, the pyramidal neurons are loosely packed as revealed by the Nissl counterstain. Theasterisks indicate where the CA1 pyramidal cell layer divides into two heterotopic principal layers. Note that somatostatin cells (indicated by the solid arrows) are found in the region between the two principal cell layers as well as in the stratum radiatum proper. The hilus and CA3 distribution of SOM interneurons remained normal in Lis1+/− murine brains. Scale bars:A1, 325 μm; A2, 125 μm;B1, 365 μm; B2, 135 μm;C1, 315 μm; C2, 125 μm;D1, 300 μm; D2, 100 μm.