Receptors olfactory bulb

The effects of VIP and PACAP are mediated by three GPCR subtypes, VIP, VIP2, and PACAP receptor, coupled to the activation of adenjiate cyclase (54). The VIP subtype is localized ia the lung, Hver, and iatestiae, and the cortex, hippocampus, and olfactory bulb ia the CNS. The VIP2 receptor is most abundant ia the CNS, ia particular ia the thalamus, hippocampus, hypothalamus, and suprachiasmatic nucleus. PACAP receptors have a wide distribution ia the CNS with highest levels ia the olfactory bulb, the dentate gyms, and the cerebellum (84). The receptor is also present ia the pituitary. The VIP and PACAP receptors have been cloned. 

Alternate ways to interfere with the orexin system may be via inhibition of dipeptidyl peptidases or proteolysis-resistant peptide analogs as shown for other peptides. This could prolong and boost orexinergic signaling. OX-A but not OX-B can enters the brain by simple diffusion via the blood-brain barrier. Abundance of orexins and their receptors in the olfactory bulb and throughout all parts of the central olfactory system may offer transnasal routes for drug application. 

Hayashi S Momiyama A., Ohishi H Ogawameguro, R. et al. (1993). Role of metabotrophic glutamate receptor in synaptic modulation in accessory olfactory bulb. Nature 366, 687-690. 

Jia C., Goldmann J. and Halpem M. (1997). Development of vomeronasal receptor neurons subclasses and establishment of topographic projection to accessory olfactory bulb. Dev Brain Res 102, 209-216. 

Jia C. and Halpem M. (1996). Subclasses of vomeronasal receptor neurons differential expression of G-proteins (Gi-alpha2 Go-alpha) and segregated projections to the accessory olfactory-bulb. Brain Res 719, 117-128. 

FIGURE 15-7 Regional distribution of mRNAs encoding the five NMDA receptor genes in adult rat brain, by in situ hybridization. OB, olfactory bulb Cx, cortex Hi, hippocampus Cb, cerebellum Th, thalamus St, striatum. (With permission from Nakanishi, S. Science 258,597-603,1992.)... 

Odor discrimination could involve a very large number of different odorant receptors, each specific for one or a small set of odorants 818 The information generated by hundreds of different receptor types must be organized to achieve a high level of olfactory discrimination 820 Zonal expression of olfactory receptors 821 Convergence of sensory neurons onto a few glomeruli in the olfactory bulb 821... 

FIGURE 50-1 A schematic diagram of the olfactory epithelium. The initial events in odor perception occur in the olfactory epithelium of the nasal cavity. Odorants interact with specific odorant receptors on the lumenal cilia of olfactory sensory neurons. The signals generated by the initial binding events are transmitted along olfactory neuron axons to the olfactory bulb of the brain. 

Astic, L., Saucier, D. and Holley, A. Topographical relationships between olfactory receptor cells and glomerular foci in the rat olfactory bulb. Brain Res. 424 144—152, 1987. 

Nusser, Z., Kay, L. M., Laurent, G Homanics, G. E., and Mody, I. (2001) Disruption of GABAa receptors on GABAergic intemeurons leads to increased oscillatory power in the olfactory bulb network../. Neurophysiol. 86,2823-2833. 

An important insight from many studies (28) is that the response patterns—the molecular images—at various levels in the central olfactory pathway are set up by the differential responses of the ORCs in the peripheral receptor epithelium. These studies also suggest that functional modules, which may correspond to recognizable structural units such as individual glomeruli with their associated cells, in the olfactory bulb or lobe participate in the analysis of olfactory information conveyed to them... 

The KS mutations were identified in the KAL gene and result in abnormal olfactory bulb development (99,100). The mutations responsible for the X-linked IHH with adrenal hypoplasia congenita were identified in the DAXl gene. DAXl encodes an orphan nuclear hormone receptor that regulates portions of reproductive development (101,102). 

The olfactory epithelium of mammals contains many types of olfactory neurons, each expressing a specific odorant receptor. Linda Buck has shown that an odorant can activate multiple distinct receptors and that a receptor can be activated by multiple odorants. Thus, there must exist a combinatorial mechanism for odor detection some sort of pattern recognition. The axons of olfactory neurons converge on glomeruli in the olfactory bulb. There, incoming signals are integrated and the sense of smell is created. 

The dendrites on the receptor cells have swellings, the olfactory knobs. These knobs have smooth vesicles that may be open to the mucus covering the epithelium. From each knob extend 1 to 150 cilia, floating in the mucus. The precise number of cilia varies with the species. The rabbit, for example, has 10-12 cilia on each knob. The surrounding mucus consists of mucopolysaccharides, lipids, and phosphatides. The axons of the olfactory receptor cells extend through the cribriform plate and terminate in the olfactory bulb (Fig. 5.1). 

---