Olfactory bulb mitral cells

Cerebral cortex (layer I-VI, selected interneurons and principal cells) hippocampus (selected interneurons and principal cells) pallidum striatum (interneurons) thalamic relay nuclei olfactory bulb (mitral cells and interneurons) cerebellum (Purkinje cells and granule cells) deep cerebellar nuclei amygdala basal forebrain substantia nigra pars reticulata inferior colliculus brainstem... 

Ennis M, Zhu M, Heinbockel T, Hayar A. 2006. Olfactory nerve-evoked metabotropic glutamate receptor-mediated responses in olfactory bulb mitral cells. J Neurophysiol 95 2233-2241. 

Heinbockel T, Heyward P, Conquet F, Ennis M. 2004. Regulation of main olfactory bulb mitral cell excitability by metabotropic glutamate receptor mGluR 1. J Neurophysiol 92 3085-3096. 

Jiang MR, Griff ER, Ennis M, Zimmer LA, Shipley MT. 1996. Activation of locus coeruleus enhances the responses of olfactory bulb mitral cells to weak olfactory nerve input. J Neurosci 16 6319-6329. 

Schoppa NE, Westbrook GL. 1997. Modulation of mEPSCs in olfactory bulb mitral cells by metabotropic glutamate receptors. J Neurophysiol 78 1468-1475. 

Olfactory system Main olfactory bulb Mitral cells +++ +++... 

Rubin, D.B., Cleland, T.A. Dynamical mechanisms of odour processing in olfactory bulb mitral cells. J. Neurophysiol. 96(2), 555-568 (2006)... 

Hgure 6. Chemorepulsion of mitral cell axons by septum. (A) Axon growth pattern of mitral cells in the olfactory bulb. Mitral cell axons grow laterally away from the septum and form the lateral olfactory tract in the lateral telencephalon. (B) Collagen gel coculture of olfactory bulb explants with septal explants. 

Zippel H., Gloger M., Luthje L., Nasser S., et al. (2000). Pheromone discrimina ability of olfactory bulb mitral and ruffed cells in the goldfish. Chem Senses 339-349. 

Price JL, Powell TPS. 1970b. The mitral and short axon cells of the olfactory bulb. J Cell Sci 7 631-651. 

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... 

Farther upstream in the olfactory system, the projection neurons from the olfactory bulb (mitral and tufted cells) distribute themselves to myriad destinations [19], whieh in turn project elsewhere and, in most cases, send a return link to the originating location [19]. These distributed projection pathways allow for numerous influences on behavior e.g., the odorant can be spoken about, presumably because of connections to cortex [19] odors may influence mood and emotion, even at subconscious levels [20], because of diverse eonneetions to limbic structures [19] physiological, e.g., autonomic and neuroendocrine, responses may be modulated by odors, because olfaction communicates rather directly with the hypothalamopitui-tary gonadal axis [21]. 

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,... 

Jia C.P. and Halpem M. (1997). Segregated populations of mitral/tufted cells in the accessory olfactory bulb. Neuroreport 8, 1887-1890. 

Meisami E., Mikhail L Bairn D. and Bhatnagar K.R (1998). Human olfactory bulb aging of glomeruli and mitral cells and a search for the accessory olfactory bulb. In Olfaction and Taste, Xll (Murphy C., ed.), Ann NY Acad Sci 855, 708-715. 

By contrast, the accessory olfactory system is thought to be involved in the detection of odors that influence a variety of reproductive and aggressive behaviors (Keverne 1999). Sensory neurons are located in the vomeronasal organ (VNO) and detect pheromones which gain access to the VNO by a pumping mechanism (Meredith and O Connell, 1979). VNO neurons send projections to the accessory olfactory bulb (AOB). Mitral cells of the AOB project in turn to the medial nucleus of the amygdala olfactory information is then dispatched to several hypothalamic regions such as the bed nucleus of the stria terminalis, the medial preoptic area and the ventromedial hypothalamus (Scalia and Winans 1975). 

Olfactory glomeruli must have evolved early, because these characteristic structures are present in the "olfactory brains" of modem representatives of ancient marine groups including molluscs (5) and crustaceans (6). Likewise the lampreys, which are extant representatives of the most primitive vertebrates, have relatively large olfactory bulbs with glomeruli and conspicuous mitral cells not unlike those of more advanced vertebrates (7). 

The olfactory bulb contains glomeruli where the dendrites of mitral cells and tufted cells concentrate. The mouse has about 1800 glomeruli in its olfactory bulb. In the rabbit, the input from 5 x 10 receptor cells converges on 1900 glomeruli (Fig. 5.7). In some bats, 900 receptor cells converge on each secondary olfactory neuron. 

Odor exposure during early ontogeny (e.g. 2-week-old rats) alters the mitral cells in specific regions of the olfactory bulb (D0ving and Pinching, 1973 ... 

Yuan Q, Harley CW, McLean JH. Mitral cell betal and 5-HT2A receptor colocalization and cAMP coregulation a new model of norepinephrine-induced learning in the olfactory bulb. Learn Mem 2003 10 5-15. 

Mitral and tufted cells in the olfactory bulb project their axons to the olfactory cortex, the site thought to integrate the signals from distinct glomeruli. The olfactory signals processed in the olfactory cortex are sent to a variety of higher centers of the brain, which include insular cortex, orbitofrontal cortex, amygdale, hippocampus, and the nucleus accumbens.205... 

Fig. 3 Vomeronasal system. Schematic representation of a rodent nasal cavity and brain (lateral view). Accessory olfactory bulb (AOB) mitral cells project to vomeronasal and extended amygdala. Inset The VNO is a bilateral tubular structure located at the base of the nasal septum. VSNs that express the same V1R or V2R converge on a small number of glomeruli in the AOB. Sensory neurons located in the apical layer of the epithelium project to the anterior part of the AOB, whereas those present in the basal layer project to the posterior part. MOE main olfactory epithelium, MOB main olfactory bulb, BSTMPM posteromedial bed nucleus of the stria terminalis, MEA medial amygdaloid nucleus, BACfF bed nucleus of the accessory olfactory tract, PMCO posteromedial cortical amygdaloid area...

Salazar I, Brennan PA (2001) Retrograde labelling of mitral/tufted cells in the mouse accessory olfactory bulb following local injections of the lipophilic tracer Dil into the vomeronasal amygdala. Brain Res 896 198-203... 

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