Regional and cellular localization of the sst2A receptor immunoreactivity in sagittal sections of the rat rhombencephalon at embryonic day 13 (E13).

<p>A) Densely packed sst2A receptor-immunoreactive cells are observed in the marginal zone contiguous to the ventricular zone of the rhombomeres (r1 to r6, arrowheads) and in the lateral reticular formation (LRtF). B–B″) Sst2A receptor-immunoreactive cells (red) are localized in the marginal zone (B) whereas proliferating cells identified by the proliferation marker Ki-67 (green) are concentrated in the ventricular zone (B′). The lack of overlap between the two signals (B″) indicates that sst2A receptor-expressing cells are predominantly post-mitotic. C) The majority of sst2A receptor-immunoreactive cells have small round perikarya and some exhibit immunolabeled processes that are oriented perpendicularly to the ventricular surface. D) A few sst2A receptor-immunoreactive cells are bipolar, displaying the morphological features of migrating neurons. E) In the LRtF, cell bodies are strongly sst2A receptor-immunoreactive. F–F″) An sst2A receptor-immunoreactive cell (red in F, F″) of the LRtF is found to be Ki-67-positive (green in F′, F″) (arrowheads). The low percentage of colocalization (F″) indicates that the majority of receptor-expressing cells are post-mitotic. G–G″) The post-mitotic feature of most sst2A receptor-immunoreactive cells (red in G, G″) of the rhombencephalon is further indicated by the colocalization (G″) with the post-mitotic neuronal marker β-tubulin (green in G′, G″) (arrowheads), as illustrated in the facial nucleus. Scale bars: A, 250 µm; B–B″, G–G″, 50 µm; C, E, 20 µm; F, 10 µm.