Main olfactory bulb granule 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. 

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).

Yu, G.-Z., Kaba, H., Okutani, F., Takahashi, S., Higuchi, T., Seto, K. 1996. The action of oxytocin originating in the hypothalamic paraventricular nucleus on mitral and granule cells in the rat main olfactory bulb. Neuroscience, 72, 1073—1082. 

Central/Tertiary structures The fish olfactory bulb is a fourlayered structure much as in higher vertebrates. Within the 2nd layer, the first synapse for olfactory input is on the dendrites of the mitral cells (MC). About 1000 ORN axons converge on one MC, a ratio similar to mammals. The MC output, from cells at various levels, leads into several glomeruli and receives (inhibitory) input from granule cells. The latter also innervate a distinct cell type in the MC layer of teleosts — the ruffed cells (RC), with which they have reciprocal synapses [Fig. 2.18(a)] both relay cells send ascending fibres to forebrain centres (Kosaka and Hama, 1982). The RC are unlike the MC since they are not stimulated by the ORNs directly. Their interactions (Chap. 5) may contribute to the processing of pheromonal stimuli (Zippel, 2000). The main bulbar pathways project to several nuclei in the forebrain via two ipsilateral tracts, the lateral and medial [Fig. 2.18(b)], the latter mediates sexual behaviour and the former probably other behaviours (Hara,... 

Gouda M., Matsutani S Senba E. and Tohyama M. (1990). Peptidergic granule cell populations in the rat main and accessory olfactory bulb. Brain Res 512, 339-342. 

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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