Compensatory plasticity in the olfactory epithelium: age, timing, and reversibility

Barber, Casey N.; Coppola, David M.

doi:10.1152/jn.00076.2015

Cited by 13 publications

(15 citation statements)

References 41 publications

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“…Our methods have been described in detail previously (Waggener and Coppola, 2007; Coppola et al, 2013, 2017; Barber and Coppola, 2015) and will only be briefly described here.…”

Section: Methodsmentioning

confidence: 99%

Tests of the chromatographic theory of olfaction with highly soluble odors: a combined electroolfactogram and computational fluid dynamics study in the mouse

et al. 2019

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The idea that the vertebrate nasal cavity operates like a gas chromatograph to separate and discriminate odors, referred to herein as the ‘chromatographic theory’ (CT), has a long and interesting history. Though the last decade has seen renewed interest in the notion, its validity remains in question. Here we examine a necessary condition of the theory: a correlation between nasal odor deposition patterns based on mucus solubility and the distribution of olfactory sensory neuron odotypes. Our recent work in the mouse failed to find such a relationship even across large sorption gradients within the olfactory epithelium (OE). However, these studies did not test extremely soluble odorants or low odor concentrations, factors that could explain our inability to find supporting evidence for the CT. The current study combined computational fluid dynamics (CFD) simulations of odor sorption patterns and electro-olfactogram (EOG) measurements of olfactory sensory neuron responses. The odorants tested were at the extremes of mucus solubility and at a range of concentrations. Results showed no relationship between local odor sorption patterns and EOG response maps. Together, results again failed to support a necessary condition of the CT casting further doubt on the viability of this classical odor coding mechanism.

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“…Our methods have been described in detail previously (Waggener and Coppola, 2007; Coppola et al, 2013, 2017; Barber and Coppola, 2015) and will only be briefly described here.…”

Section: Methodsmentioning

confidence: 99%

Tests of the chromatographic theory of olfaction with highly soluble odors: a combined electroolfactogram and computational fluid dynamics study in the mouse

et al. 2019

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“…Recording setup. Recording procedures have been described previously (Barber and Coppola 2015;Coppola et al 2013). Briefly, recordings took place within a Faraday cage covered with plastic sheeting.…”

Section: Methodsmentioning

confidence: 99%

Tests of the sorption and olfactory “fovea” hypotheses in the mouse

Coppola

Ritchie

Craven

2017

Journal of Neurophysiology

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The spatial distribution of receptors within sensory epithelia (e.g., retina and skin) is often markedly nonuniform to gain efficiency in information capture and neural processing. By contrast, odors, unlike visual and tactile stimuli, have no obvious spatial dimension. What need then could there be for either nearest-neighbor relationships or nonuniform distributions of receptor cells in the olfactory epithelium (OE)? Adrian (Adrian ED. 100: 459-473, 1942; Adrian ED. 6: 330-332, 1950) provided the only widely debated answer to this question when he posited that the physical properties of odors, such as volatility and water solubility, determine a spatial pattern of stimulation across the OE that could aid odor discrimination. Unfortunately, despite its longevity, few critical tests of the "sorption hypothesis" exist. Here we test the predictions of this hypothesis by mapping mouse OE responses using the electroolfactogram (EOG) and comparing these response "maps" to computational fluid dynamics (CFD) simulations of airflow and odorant sorption patterns in the nasal cavity. CFD simulations were performed for airflow rates corresponding to quiet breathing and sniffing. Consistent with predictions of the sorption hypothesis, water-soluble odorants tended to evoke larger EOG responses in the central portion of the OE than the peripheral portion. However, sorption simulation patterns along individual nasal turbinates for particular odorants did not correlate with their EOG response gradients. Indeed, the most consistent finding was a rostral-greater to caudal-lesser response gradient for all the odorants tested that is unexplained by sorption patterns. The viability of the sorption and related olfactory "fovea" hypotheses are discussed in light of these findings. Two classical ideas concerning olfaction's receptor-surface two-dimensional organization-the sorption and olfactory fovea hypotheses-were found wanting in this study that afforded unprecedented comparisons between electrophysiological recordings in the mouse olfactory epithelium and computational fluid dynamic simulations of nasal airflow. Alternatively, it is proposed that the olfactory receptor layouts in macrosmatic mammals may be an evolutionary contingent state devoid of the functional significance found in other sensory epithelia like the cochlea and retina.

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“…In compensatory plasticity, OSN sensitivity to odors increases when odor stimulation is blocked. For example, within 2 weeks of UNO, the ipsilateral olfactory epithelium becomes more sensitive to odor stimulation (Barber and Coppola 2015). Importantly, this effect is reversible.…”

Section: Osn Synapsesmentioning

confidence: 99%

“…The increased strength of ipsilateral OSN synapses after UNO can be viewed as part of a homeostatic compensatory plasticity response in OSNs (Barber and Coppola 2015). In compensatory plasticity, OSN sensitivity to odors increases when odor stimulation is blocked.…”

Section: Osn Synapsesmentioning

confidence: 99%

Activity-Dependent Gene Expression in the Mammalian Olfactory Epithelium

et al. 2017

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Activity-dependent processes are important to olfactory sensory neurons (OSNs) in several ways, such as cell survival and the specificity of axonal convergence. The identification of activity-dependent mRNAs has contributed to our understanding of OSN axon convergence, but has revealed surprisingly little about other processes. Published studies of activity-dependent mRNAs in olfactory mucosae overlap poorly, but by combining these agreements with meta-analysis of existing data we identify 443 mRNAs that respond to methods that alter OSN activity. Three hundred and fifty of them are expressed in mature OSNs, consistent with the expectation that activity-dependent responses are cell autonomous and driven by odor stimulation. Many of these mRNAs encode proteins that function at presynaptic terminals or support electrical activity, consistent with hypotheses linking activity dependence to synaptic plasticity and energy conservation. The lack of agreement between studies is due largely to underpowered experiments. In addition, methods used to alter OSN activity are susceptible to indirect or off-target effects. These effects deserve greater attention, not only to rigorously identify OSN mRNAs that respond to altered OSN activity, but also because these effects are of significant interest in their own right. For example, the mRNAs of some sustentacular cell enzymes believed to function in odorant clearance (Cyp2a4 and Cyp2g1) are sensitive to unilateral naris occlusion used to reduce odorant stimulation of the ipsilateral olfactory epithelium. Also problematic are odorant receptor mRNAs, which show little agreement across studies and are susceptible to differences in frequency of expression that masquerade as activity-dependent changes in mRNA abundance.

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Compensatory plasticity in the olfactory epithelium: age, timing, and reversibility

Cited by 13 publications

References 41 publications

Tests of the chromatographic theory of olfaction with highly soluble odors: a combined electroolfactogram and computational fluid dynamics study in the mouse

Tests of the chromatographic theory of olfaction with highly soluble odors: a combined electroolfactogram and computational fluid dynamics study in the mouse

Tests of the sorption and olfactory “fovea” hypotheses in the mouse

Activity-Dependent Gene Expression in the Mammalian Olfactory Epithelium

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