Fig. 3
From: Gradual transition of pyramidal cell types in the dorsal hippocampal area CA2b of the C57BL/6 mouse
PCP4-positive neurons in CA2b show large spiny protrusions, and rarely also thorny excrescences, in stratum lucidum. (a) Overview maximum-Z-projection of the injected CA2 region showing the relative position of a PCP4-positive neuron in CA2b. (a’) The cell body is positive for PCP4. White boxes indicate the regions magnified in a’ and b. (b) Magnification of the proximal apical tree. White boxes indicate the regions further magnified in c1-4. (c) Spiny protrusions with large heads (filled arrow) are visible alongside some classical spines (open arrow) in SL (c1, c2). Bigger spiny protrusions with a more lobular structure reminiscent of complex spines are also visible (c3, c4; filled arrows). Note the emergence of classical spines (arrowheads) as the apical tree enters SR (c2, c4). (d) Two adjacent sections showing a PCP4-positive neuron in distal CA2b carrying several large thorny excrescences (TEs). For visualization purposes, the maximum-Z-projection of the labeled neuron (Alexa 568) is overlayed with only the one PCP4 channel image plane of the stack that contains the cell body of the labeled neuron. The cell body (d1) is clearly PCP4-positive. The proximal apical tree on the adjacent reslice (d2) displays the excrescences (red filled arrows), part of which can also be seen in d1. (e) Magnification of d2. The TEs (red filled arrows) as well as several larger spinous protrusions (white filled arrows) are clearly visible. The dendrites are densely covered with classical spines upon entering SR (arrows). (f) Magnification of the large TEs visible in e, followed through four consecutive image planes of the stack. SO – stratum oriens; SP – stratum pyramidale; SL – stratum lucidum; SR – stratum radiatum; CA – cornu ammonis.
