Odorant receptor expression patterns are restored in lesion-recovered rat olfactory epithelium.

Lesions of the olfactory periphery provide a means for examining the reconstitution of a diverse and highly regulated population of sensory neurons and the growth, en masse, of nascent axons to the bulb. The olfactory epithelium and its projection onto the bulb are reconstituted after ablation by methyl bromide gas, and some measure of olfactory function is restored. The extent to which the system regenerates the full repertoire of odorant receptor-expressing neurons, particularly their spatially restricted distribution across the epithelial sheet, is unknown, however, and altered odorant receptor expression might contribute to the persistent distortion of odorant quality that is observed in the lesioned-recovered animals. To address the question of receptor expression in the recovered epithelium, we performed in situ hybridization with digoxigenin-labeled riboprobes for eight odorant receptors on the olfactory epithelium from unilaterally methyl bromide-lesioned and control rats. The data demonstrate that the distribution of sensory neuron types, as identified and defined by odorant receptor expression, is restored to normal or nearly so by 3 months after lesion. Likewise, the numbers of probe-labeled neurons in the lesioned-recovered epithelium are nearly equivalent to the unlesioned side at this time. Finally, our evidence suggests that odorant receptors are distributed in multiple overlapping bands in the normal, unlesioned, and lesioned-recovered epithelium rather than in the conventionally accepted three or four zones. Thus, the primary sensory elements required for functional recovery of the olfactory system after damage are restored, and altered function implies the persistence of a more central failure in regeneration.

Effectiveness of gabapentin for treatment of burning mouth syndrome.

Burning mouth syndrome is a debilitating disorder involving oral pain that may have at least 4 underlying causes. Although several treatments have been proposed, none seems to be universally effective. We report the case of a 67-year-old woman with unremitting oral burning that is increased with the application of anesthetic agents. Initial treatments with nortriptyline hydrochloride and sertraline hydrochloride were contraindicated because of adverse effects, but the administration of gabapentin significantly reduced oral burning. The present case illustrates the effectiveness of gabapentin as a treatment of burning mouth syndrome.

The relationship between metacognitive awareness of olfactory ability and age in people reporting chemosensory disturbances.

When determining how much to rely on olfactory information, accurate estimates of olfactory ability are important. Nevertheless, metacognitive errors regarding olfactory ability are common in the normal population. Are older adults less accurate at estimating olfactory ability, or do they simply tend to make a particular type of estimation error? We examined data from 203 patients, all of whom self-rated olfactory ability and then were tested with the Odorant Confusion Matrix. The patients' self-reports did not match the objective measure of olfactory ability in 42% of the cases, thus demonstrating a high level of impairment in metacognitive knowledge. Neither the cause of loss nor the patient's age was related to the inability to accurately estimate olfactory loss, but both contributed to the type of metacognitive errors patients made. Younger patients tended to underestimate their olfactory ability, thus behaving similarly to patients with "blindsight" who demonstrate residual visual function in the absence of awareness. Older patients tended to overestimate their olfactory ability, thus making the metacognitive error of deficit unawareness that is observed in a number of other clinical syndromes. These findings indicate that older patients are not necessarily more likely to make errors in estimating their olfactory ability; rather, they are more prone to a particular type of metacognitive error than are younger patients.

Experimental and numerical determination of odorant solubility in nasal and olfactory mucosa.

Odorant deposition in the nasal and olfactory mucosas is dependent on a number of factors including local air/odorant flow distribution patterns, odorant mucosal solubility and odorant diffusive transport in the mucosa. Although many of these factors are difficult to measure, mucosal solubility in the bullfrog mucus has been experimentally determined for a few odorants. In the present study an experimental procedure was combined with computational fluid dynamic (CFD) techniques to further describe some of the factors that govern odorant mucosal deposition. The fraction of odorant absorbed by the nasal mucosa (eta) was experimentally determined for a number of odorants by measuring the concentration drop between odorant 'blown' into one nostril and that exiting the contralateral nostril while the subject performed a velopharyngeal closure. Odorant concentrations were measured with a photoionization detector. Odorants were delivered to the nostrils at flow rates of 3.33 and 10 l/min. The velopharyngeal closure nasal air/odorant flows were then simulated using CFD techniques in a 3-D anatomically accurate human nose modeland the mucosal odorant uptake was numerically calculated. The comparison between the numerical simulations and the experimental results lead to an estimation of the human mucosal odorant solubility and the mucosal effective diffusive transport resistance. The results of the study suggest that the increase in diffusive resistance of the mucosal layer over that of a thin layer of water seemed to be general and non-odorant-specific; however, the mucosa solubility was odorant specific and usually followed the trend that odorants with lower water solubility were more soluble in the mucosa than would be predicted from water solubility alone. The ability of this approach to model odorant movement in the nasal cavity was evaluated by comparison of the model output with known values of odorant mucosa solubility.