ResultsDistribution of olfactory bulb astrocytes and tyrosine hydroxylase-expressing neurons. To analyze the distribution of OB astrocytes and TH-expressing neurons in the GL and EPL by immunohistochemistry, we used TH-Cre × tdTomato fl/fl mice and aimed to visualize astrocytes by anti-GFAP staining. GFAP-positive astrocytes were located throughout the GL, which can be distinguished from the ONL by glomerular structures, and the EPL, in which GFAP-expression was weaker compared to the GL (Fig. 1A). TH expression also exhibits its highest density in the GL, but the EPL also contains some TH-positive neurons and neuronal processes (Fig. 1A).In the glomerular layer, dendrites of tdTomato-positive SA cells are closely intermingled with astrocyte processes, suggesting a possible physiological interaction such as neurotransmitter release by SA cells and subsequently activation of astrocytic dopamine receptors (Fig. 1B,C). Close proximity of dendrites of TH-positive neurons and astrocyte processes could also be observed in the EPL, albeit at a lower density (Fig. 1D). In both layers, astrocyte processes were in direct vicinity of tdTomato-positive varicosities, presumptive dopamine release sites 18 . Scientific RepoRtS |(2020) 10:631 | https://doi.