Odor responses

None of the foregoing methods will tell the frequency or duration of exposure of any receptor to irritant or odorous gases when each such exposure may exceed the irritation or odor response threshold for only minutes or seconds. The only way that such an exposure can be measured instrumentally is by an essentially continuous monitoring instrument, the record from which will yield not only this kind of information but also all the information required to assess hourly, daUy, monthly, and annual phenomena. Continuous monitoring techniques may be used at a particular location or involve remote sensing techniques. 

Hatanaka T. and Matsuzaki O. (1993). Odor responses of the vomeronasal system in Reeve s turtle, Geoclemys Reevesii. Brain Behav Evol 41, 183-186. 

Dalton, Pamela, and Gary K. Beauchamp. Establishment of Odor Response Profiles Ethnic, Racial and Cultural Influences. Philadelphia, PA Monell Chemical Senses Center, February 4, 1999. 

FIGURE 50-5 A model for the transduction of odors in OSNs. The individual steps are detailed in the text. Note that several feedback loops modulate the odor response, including inhibition of the CNG channel by Ca2+ ions (purple balls) that permeate the channel, and a Ca2+/calmodulin (CaM) -mediated desensitization of the channel that underlies rapid odor adaptation. Several other mechanisms, including phosphodiesterase-mediated hydrolysis of the second messenger, cAMP, and phosphorylation of the OR by various kinases, have also been described. 

Other mechanisms have also been implicated in odor adaptation, including cAMP-dependent phosphorylation of ciliary proteins via protein kinase A G-protein-receptor kinase activity (GRK3), possibly via phosphorylation of the OR Ca2+/calmodulin kinase II (CaMKII) phosphorylation of ACIII cGMP and carbon monoxide [ 31 ]. These latter three mechanisms have been particularly linked to longer-lasting forms of adaptation, on the order of tens of seconds (for CaMKII) or minutes (CO/cGMP). Together with the short-term adaptation described above, these various molecular mechanisms provide the OSN with a number of ways to fine-tune odor responses over time. 

Particularly alarming are fetal effects of alcohol and drugs on food-related odor responses in humans. Apart from the severe fetal alcohol syndrome, alcohol can affect the chemosensory behavior of a fetus. Alcohol administered to pregnant female rats impaired odor aversions and preferences in their offspring. A... 

Sensory development points to the importance of chemical cues veiy early in life after birth. From the fourth day of life, mouse pups respond to the odor of their nest (Schmidt etal., 1986). In rats, the main olfactory system processes odor responses during the first days of life. 

Duchamp-Viret, P., Chaput, M. A. and Duchamp, A. (1999). Odor response properties of rat olfactory receptor neurons. Science 284,2171-2174. 

Many common VOCs have well-documented health effects at elevated levels. In most indoor environments however, the exposure is described as low since concentrations are negligible in comparison to occupational limit values. Sensory responses to VOCs also include odor response, nasal irritation (pungency) and eye irritation ( Devos et al., 1990 and Cometto-Mu iz and Cain, 1990). The maximum concentrations determined in Singapore buildings were compared with some of the common health and comfort guidelines. The values are presented in Table 10.5. It is observed that the maximum concentrations for the majority of the target compounds are within recommended guidelines. Levels are very low as compared to threshold limit values related to health and irritation. 

This chapter will discuss the isolation of Drosophila odorant receptor (DOR) genes, how these genes have expanded our understanding of the development and functional anatomy of the olfactory system, how the odor response profiles of OSNs respond to odorants, and the mechanisms by which odor-specific activity is relayed to the brain. 

Riesgo-Escovar J., Raha D. and Carlson J. R. (1995) Requirement for a phospholipase C in odor response overlap between olfaction and vision in Drosophila. Proc. Natl. Acad. Sci. USA 28, 2864-2868. 

Selzer (1981) found that components of a complex food odor did not activate a single ORN independently from each other. Mixtures of odorants interact when stimulating ORNs to produce less (mixture suppression) or more (synergism) activity then would be expected from a simple competitive binding model. The transduction mechanisms that underlie the difference in temporal firing properties and inhibitory odor responses are likely to cause interactions when such odorants are combined as a single stimulus. 

Clyne P. J., Grant A. J., O Connell R. J. and Carlson J. R. (1997) Odorant response of individual sensilla on the Drosophila antenna. Invertebrate Neurosci. 3, 127-135. 

Wang L, Chen L, Jacob T. Evidence for peripheral plasticity in human odor response. J. Physiol. 2004 554 236-244. 

Horiano WB, Vaidehi N, Goddard WA 111, Singer MS, Shepherd GM. Molecular mechanisms underlying differential odor responses of a mouse olfactory receptor. Proc. Natl. Acad. Sci. U.S.A. 2000 97 10712-10716. 

Moreover, this pattern of neuronal connection was found to be identical in all mice examined. Thus, neurons that express specific ORs are linked with specific sites in the brain. This property creates a spatial map of odorant-responsive neuronal activity within the olfactory bulb. 

Roasting of the rather odourless sesame seeds generates an intense aroma characterised by roasty, burnt, meat-like or sulphurous odour notes. Several studies have been performed to identify the odorants responsible for these notes in roasted white and black sesame [97-99]. The results obtained for moderately roasted white sesame are presented in Table 6.51 as an example. 

Odor Responses from the Cellular to the Behavioral Level... 

Taken together, the fish olfactory bulb provides for the opportunity to study functionally segregated responses of all olfactory receptor neurons in a recepto-topic map. Due to the small size and semi-transparent nature of the zebrafish olfactory bulb, it is to be expected that odor responses of all three receptor neuron populations could be measured simultaneously and possibly identified by spatial position. Indeed, in the zebrafish olfactory bulb it has been possible to measure odor responses in lateral, medial, and ventral glomeruli (Friedrich and Korsching 1997, 1998). 

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