Mitral cells in the olfactory bulb of adult zebrafish (Danio rerio): Morphology and distribution

Abstract

The mitral cell is the primary output neuron and central relay in the olfactory bulb of vertebrates. The morphology of these cells has been studied extensively in mammalian systems and to a lesser degree in teleosts. This study uses retrograde tract tracing and other techniques to characterize the morphology and distribution of mitral cells in the olfactory bulb of adult zebrafish, Danio rerio. These output neurons, located primarily in the glomerular layer and superficial internal cell layer, had variable-shaped somata that ranged in size from 4-18 microm in diameter and 31-96 microm2 in cross-sectional area. The mitral cells exhibited two main types of morphologies with regard to their dendrites: the unidendritic morphology was a single primary dendrite with one or more tufts, but multidendritic cells with several dendritic projections also were seen. The axons of these cells projected to either the medial or the lateral olfactory tract and, in general, the location of the cell on the medial or lateral side of the bulb was indicative of the tract to which it would project. Further, this study shows that the majority of zebrafish mitral cells likely innervate a single glomerulus rather than multiple glomeruli. This information is contrary to the multiple innervation pattern suggested for all teleost mitral cells. Our findings suggest that mitral cells in zebrafish may be more similar to mammalian mitral cells than previously believed, despite variation in size and structure. This information provides a revised anatomical framework for olfactory processing studies in this key model system.

Development of the serotoninergic system in the central nervous system of a shark, the lesser spotted dogfish Scyliorhinus canicula

“…This antibody was used for staining catecholaminergic cells in a wide range of vertebrate species from dogfish to humans. In zebrafish (McLean and Fetcho, 2004a,b;Fuller et al, 2006) and dogfish (Sueiro et al, 2003(Sueiro et al, , 2007Carrera et al, 2005) it has been shown to stain only well-characterized catecholaminergic cells consistent with known catecholaminergic neurons in other species .…”

From the Olfactory Bulb to Higher Brain Centers: Genetic Visualization of Secondary Olfactory Pathways in Zebrafish

“…However, a recent study (Fuller et al, 2006) reported a revised description of zebrafish MC morphology in which the majority of retrogradely labeled MCs have a single primary dendrite with a discrete tuft and a smaller proportion of MCs showing the multidendritic morphology also innervates a single glomerulus. This notion was supported by the present result that the vast majority of genetically labeled single MCs (31 of 32 MCs) showed the uni-dendritic morphology, innervating only a single glomerulus.…”

Single unit responses to skin odorants from conspecifics and heterospecifics in the olfactory bulb of crucian carp Carassius carassius

“…The mitral cells located in the lateral part of the teleost OB are morphologically different from those in the medial part (Alonso et al, 1988;Fuller et al, 2006), which suggests physiological and functional distinctions. However, no differences between the medial Responses: ++, number of units responding to both skin extracts; +0, the number of units responding to the first but not the second skin extract; 0+, the number of units responding to the second but not the first skin extract; 0 0, number of units not responding to any of the two skin extracts.…”