Receptor cells, vertebrate olfactory

Constanzo R. (1991). Regeneration of olfactory receptor cells. In Regeneration of Vertebrate Sensory Cells (Bock G.R., ed.). Wiley, New York, pp. 233-248. 

Eisthen H.L. (1992). Phylogeny of the vomeronasal system and of receptor cell-types in the olfactory and vomeronasal epithelia of vertebrates. Microsc Res Tech 23, 1-21. 

Schild D. and Restrepo D. (1998). Transduction mechanisms in vertebrate olfactory receptor cells. Physiol Revs 78, 429-466. 

Even though well-characterized at a biophysical level, the mechanical transduction mechanism of hair cells is still not fully understood in molecular terms. This discrepancy is in part due to the extreme scarcity of hair cells instead of the millions or even hundreds of millions of receptor cells that the olfactory and visual systems possess, only a few tens of thousands of hair cells are found in the internal ears of most vertebrate species. The small number of hair cells and the direct transduction mechanism has greatly impeded molecular biological and... 

In fish, both taste and olfactory stimuli are waterborne. However, taste involves the seventh, ninth or tenth cranial nerves, in contrast to the first cranial nerve for smell. Elasmobranchs have their taste buds in the mouth and pharynx, but in bony fish they occur around the gills, on barbels and pectoral fins, and also scattered over the rest of the body surface. They crowd particularly in the roof of the mouth, forming the palatal organ. The taste receptor cells are arranged as a bundle to form a taste bud. Like other vertebrates, fish have receptors for sweet, sour, salty, and bitter. For instance, goldfish reject quinine-treated food pellets (Jobling, 1995). Many fish species are particularly sensitive to acidic taste characteristics. The responses of fish to amino acids will be discussed in Chapter 12. 

The long-held dichotomy of macrosmatic and microsmatic vertebrates is no longer tenable. Neuroanatomists had assumed that taxa with relatively few olfactory receptor cells and small olfactory bulbs would also be inferior in olfactoiy performance (threshold and number of compounds detected) to those with more receptors and larger bulbs. However, we now know from single-cell recordings that a particular receptor cell type can respond to a wide range of odor compounds that share certain features. Keverne (1983) pointed out that the olfactory bulbs act as a filter, while more complex pattern analysis takes place in the neocortex. The more evolved the neocortex, as in primates, the... 

Derby, C. D., Carr, W. E. S., and Ache, B. W., Purinergic olfactory receptor cells of crustaceans response characteristics and similarities to internal purinergic cells of vertebrates, /. Comp. Physiol. A, 155, 341, 1984. 

Kurahashi T. and Yau K.W. (1993) Co-existence of cationic and chloride components in odorant-induced current of vertebrate olfactory receptor cells. Nature 363, 71-75. 

Morita Y, Finger TE (1998) Differential projections of ciliated and microvillous olfactory receptor cells in the catfish, Ictalurus punctatus. J Comp Neurol 398 539-550 Nakatani Y, Takeda H, Kohara Y, Morishita S (2007) Reconstruction of the vertebrate ancestral genome reveals dynamic genome reorganization in early vertebrates. Genome Res 17 1254-1265... 

Copper exposures at 20 pg/L or higher induce degenerating effects on the olfactory receptor cells in fish (Saucier and Astic 1995). Since it is a normal process that receptor cells are regenerating in the olfactory epithelium of fish and other vertebrates as long as basal cells are present, new functional olfactory cells will be continuously produced and the animal can recover its sense of smell (e.g. Zippel 1993). There will, however, be problems if the fish remains in contaminated water and the olfactory epithelium does not acclimate and protect the receptor cells from metal toxicity (e.g. by metal-lothioneins, mucus production). It has been shown that olfactory receptor neurons can be a transport route of metal ions and organic molecules to the olfactory bulbs and the brain in vertebrates, fish included, with severe disturbing effects on the function of the CNS (e.g. Tjalve and Henriksson 1999 Persson et al. 2002). 

It should be mentioned that data on cockroach antennal (U3) and maxillar palp (jtU) olfactory sensilla show that different receptor cells display consistently different sensitivities towards the same ranges of n-alcohols (e.g. so called pentano and heptanol receptors). Additionally, the existence of vertebrate olfactory receptor cells which display different sensitivities for the same alcohols can be concluded from single-unit adaptation and cross adaptation studies ( ). Although the effects could be due to different protein receptor species, they can also be explained on the basis of different lipid compositions in the receptor cells in question. 

Eisthen, H.L. 1992. Phylogeny of the vertebrate olfactory and vomeronasal systems and their receptor cells. Micr. Res. Tech. 23, 1-21. 

Figure 2 Depiction of some components of the vertebrate olfactory epithelium in the nose. Odorants, e.g., carvone, deposit themselves in the mucous layer and interact with molecular receptors in the membrane of cilia of the olfactory receptor cells. Subsequent to intracellular signal transduction events, action potentials are sent via the olfactory axons to the olfactory bulbs in the brain. Supporting cells provide physical and physiological support for the olfactory neurons. Undifferentiated basal (stem) cells are the source of new supporting and olfactory receptor cells.

Carr WES, Gleeson RA, Ache BW, Milstead ML (1986) Olfactory receptors of the spiny lobster ATP-sensitive cells with similarities to P2-type purinoceptors of vertebrates. J Comp Physiol A 158 331-338... 

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