Crypt Cells of the Zebrafish Danio rerio Mainly Project to the Dorsomedial Glomerular Field of the Olfactory Bulb

Department of Cell and Molecular Biology, Faculty of Sciences, University of A Coruña, A Coruña, Spain.
Chemical Senses (Impact Factor: 3.16). 12/2011; 37(4):357-69. DOI: 10.1093/chemse/bjr109
Source: PubMed


The olfactory mucosa of the zebrafish consists of 3 morphological types of olfactory receptor neurons (ORNs): ciliated, microvillous, and crypt cells. Previous studies in the zebrafish have revealed differential projections of ciliated and microvillous ORNs, which project to different glomerular fields. However, the bulbar targets of zebrafish crypt cells were not identified. Here, we analyze the relationship between crypt cells of the olfactory epithelium and dorsal glomerular fields of the zebrafish olfactory bulbs, as wells as the connections between these bulbar regions and forebrain regions. For this purpose, a lipophilic carbocyanine tracer (DiI) was used in fixed tissue. Application of DiI to the dorsomedial glomerular field mainly labeled crypt cells in the zebrafish olfactory epithelium. By contrast, application of DiI to the dorsolateral glomerular fields mainly labeled bipolar ORNs and only occasionally crypt cells. Bulbar efferent cells (mitral cells) contacting these dorsal glomerular fields project to different telencephalic areas, with the posterior zone of the dorsal telencephalic area (Dp) as the common target. However, dorsomedial and dorsolateral glomerular fields projected differentially to the ventral telencephalon, the former projecting to the ventrolateral supracommissural region. Retrograde labeling from the ventrolateral supracommissural region revealed mitral cells associated with 2 large glomeruli in the bulbar dorsomedial region, which putatively receives inputs from the crypt cells, indicating the existence of a crypt cell olfactory subsystem with separate projections, in the zebrafish. The comparative significance of the secondary olfactory pathways of zebrafish that convey information from crypt cells is discussed.

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    • "In this latter species, acute treatment with fluoxetine (10 mg/kg) reverts the locomotoryinhibiting effect of exposure to CAS (Barbosa et al., 2012). In the crucian carp, Schrecksreaktion is in part mediated by structures which receive primary and secondary olfactory projections which are conducted by the medial bundle of the medial olfactory tract (Hamdani et al., 2000; Døving and Lastein, 2009); in zebrafish, these projections integrate into a circuit of amygdala-like structures in the telencephalon, as well as hypothalamic structures (Gayoso et al., 2011, 2012). Serotonergic innervation of such structures has been described in zebrafish (Kaslin and Panula, 2001; Lillesaar et al., 2009), as well as monoamine oxidase activity and immunoreactivity (Anichtchik et al., 2006), the presence of 5-HT 1A -like, 5-HT 1B and 5-HT 2C receptors (Norton et al., 2008; Schneider et al., 2012), and serotonin transporters (Norton et al., 2008). "
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    • "Crypt neurons have engendered considerable interest as a third type of olfactory receptor neurons with a peculiar morphology combining elements of the other two populations, ciliated and microvilllous receptor neurons3. Several attempts have been made to elucidate their neuronal circuits, beginning with studies that sought to identify their target regions in the olfactory bulb141516171834. A cluster of mediodorsal glomeruli has been suggested as potential targets of crypt neurons, based on absence of fluorescence in some genetically labeled zebrafish lines and differential staining in others16. "
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    Scientific Reports 06/2013; 3:2063. DOI:10.1038/srep02063 · 5.58 Impact Factor
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    • "Using a double transgenic zebrafish line labeling ciliated and microvillous cells with different fluorophores, studies have shown that ciliated cells mainly project to the dorsal and medial olfactory bulb, whereas microvillous cells project to the lateral olfactory bulb (Sato et al., 2005, 2007). Retrograde labeling of the olfactory epithelium following lipophilic tracer application to different bulbar domains showed that crypt cells project to the ventral olfactory bulb in carp and to the dorsomedial olfactory bulb in zebrafish (Hamdani el and Doving, 2006; Gayoso et al., 2012). This projection pattern, shown in Figure 1, is well-conserved between the two bulbs of the same zebrafish, as well as among individual zebrafish (Baier and Korsching, 1994; Braubach et al., 2012). "
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    Frontiers in Neural Circuits 04/2013; 7:62. DOI:10.3389/fncir.2013.00062 · 3.60 Impact Factor
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