Main olfactory bulb tufted cells

Laaris N, Ennis M. 2002. Distinct activity patterns evoked by activation of mitral/tufted cell and centrifugal fiber inputs to main olfactory bulb (MOB) granule cells. Soc Neurosci Abstr 561 14. 

Macrides F, Schneider SP. 1982. Laminar organization of mitral and tufted cells in the main olfactory bulb of the adult hamster. J Comp Neurol 208 419-430. 

Schoenfeld TA, Marchand JE, Macrides E 1985. Topographic organization of tufted cell axonal projections in the hamster main olfactory bulb An intrabulbar associational system. J Comp Neurol 235 503-518. 

Fig. 5. Basic circuitry of the main olfactory bulb. Axons of ORNs form the olfactory nerve (ON). These axons terminate in the glomeruli onto mitral (M) and tufted cells (external tufted cell, ET middle tufted cell, MT) and onto juxtaglomerular neurons including periglomerular cells (PG), ET cells and short axon cells (SA). There are one way and reciprocal synapses between the apical dendritic branches of mitral and tufted cells and the dendrites of juxtaglomerular neurons (upper inset - glomerular synapses). The lateral dendrites of mitral and tufted cells form one way and reciprocal synapses with the apical dendrites of granule cells (lower inset - dendrodendritic synapses).

Fig. 8. CCK in the MOB. A-C. Silver-intensified CCK-immunohistoehemical staining in the main olfactory bulb. CCK-immunoreactive neurons are located mainly in the superficial one-third of the EPL the majority of these CCK-positive neurons are tufted cells. The apical and secondary dendrites of these cells are well delineated in the higher-power micrographs of (B) and (C). Thin axon-like processes course toward the ll L. In addition to the staining of cell bodies and dendrites, there is a dense, uniform CCK-like immunoreactive band consisting of terminal-lie puncta restricted to the IPL. Calibration bar in A = 500 fira, bar in B = 100 /tm, and bar in C = 60 /mi.

Fig. 10. Associational system in the MOB. Biocytin anterograde labeling of the inlrabulbar association system (IAS) shown in dorsal (A) to ventral (F) horizontal sections. A. The injection site (asterisk) is located in the superficial half of the EPL on the lateral side of the main olfactory bulb. B-F, Biocytin-labeled tufted cells are located in the superficial part of the EPL and the deep part of the GCL. Axons and collaterals (open arrows) are densely labeled in the IPL of the medial side of the olfactory bulb ventral to the injection site. Bar in F = 800 fim and applied to all panels.

The main olfactory bulb sends a projection to the entire extent of piriform, peri-amygdaloid and lateral entorhinal cortex (see above. Outputs of MOB). This projection terminates in the superficial half of layer I, layer la. Both mitral and tufted cells project to the rostral parts of AON and piriform cortex while the projection to more caudal parts of olfactory cortex becomes progressively dominated by mitral cells (Schoenfeld and Macrides, 1984). 

HT,a receptor is found mainly in the external plexiform layer. On the other hand, the mRNA for the S-HTja receptor has been shown by in situ hybridization to be in the mitral cell and external plexiform layers (Pompeiano et al. 1994) and more precisely, in mitral and tufted cells (McLean et al. 1994). This leads one to speculate that the dendrites or cell bodies of olfactory bulb output cells receive serotonergic input via... 

The axons of the external tufted cells project mainly to other sites in the same olfactory bulb (Schoenfeld et al. 1985). Middle and deep tufted cells also have local collaterals in the ipsilateral bulb but most of them appear to project out of the olfactory bulb to the anterior olfactory nucleus and other rostral olfactory cortical structures (Schoenfeld et al. 1985 Scott, 1986). The intrabulbar collaterals of the superficial tufted cells form... 

The axons of the mitral cells give off collaterals within the bulb in the internal plexiform and granule cell layers (Mori et al. 1983). The main axons course predominantly in the lateral olfactory tract which forms at the level of the AOB. These caudally directed axons give off collaterals in the anterior olfactory nucleus (AON) and other regions of olfactory cortex (Figs. 13, 18, 19). Tufted cells collateralize to an even greater extent in the bulb than mitral cells. The intrabulbar association pathway formed by CCK-ergic tufted cells was discussed earlier. 

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