Electro-olfactogram Responses Before and After Aversive Olfactory Conditioning in Humans

Triclosan and triclocarban weaken the olfactory capacity of goldfish by constraining odorant recognition, disrupting olfactory signal transduction, and disturbing olfactory information processing

Recently, increased production and consumption of disinfectants such as triclosan (TCS) and triclocarban (TCC) have led to massive pollution of the environment, which draws global concern over the potential risk to aquatic organisms. However, the olfactory toxicity of disinfectants in fish remains elusive to date. In the present study, the impact of TCS and TCC on the olfactory capacity of goldfish was assessed by neurophysiological and behavioral approaches. As shown by the reduced distribution shifts toward amino acid stimuli and hampered electro-olfactogram responses, our results demonstrated that TCS/TCC treatment would cause deterioration of the olfactory ability of goldfish. Our further analysis found that TCS/TCC exposure suppressed the expression of olfactory G protein-coupled receptors in the olfactory epithelium, restricted the transformation of odorant stimulation into electrical responses by disturbing the cAMP signaling pathway and ion transportation, and induced apoptosis and inflammation in the olfactory bulb. In conclusion, our results demonstrated that an environmentally realistic level of TCS/TCC would weaken the olfactory capacity of goldfish by constraining odorant recognition efficiency, disrupting olfactory signal generation and transduction, and disturbing olfactory information processing.

Investigations and Outcomes for Olfactory Disorders

Purpose of Review

To provide a detailed overview of the investigations and core outcome measures for olfactory disorders.

Recent Findings

Olfactory disorders can have a detrimental impact to the quality of life of patients. There are a wide range of causes of olfactory loss including sinonasal conditions, idiopathic, post-head trauma or infection. This review highlights the key investigations and reasoning for their use to clinically assess and research patients with olfactory disorders. In addition, this review outlines the core outcome measures for olfaction that will help inform future research in olfactory disorders.

Summary

A systematic approach with history taking and examination particularly with nasal endoscopy can determine the cause of the olfactory disorder in most cases. Specific olfactory disorder questionnaires can demonstrate the impact on quality of life, while psychophysical testing can objectively assess and monitor olfaction over time. Olfactory-evoked potentials and functional MRI are reserved for research, whereas CT and MRI imaging are used depending on history and examination. A core outcome set for olfaction has been developed that will help standardise the outcome measures used in olfaction and olfactory disorders research.

[Application research and development of objective examination of olfactory function]

The sense of smell is one of the five most primitive human sensory functions, and it plays a very important role in our daily lives. Despite numerous methods for evaluating olfactory function, there is still a lack of standardization of olfactory tests and the results are often inconsistent. Furthermore, the related research on objective evaluation started relatively late. Along with the deciphering of the olfactory pathway, the technical level of olfactory objective inspection has been greatly improved and significant progress has also been made in terms of clinical application, such as: olfactory pathway MRI and fMRI imaging, OERPs, BEAM for various olfactory disorders and early diagnosis of neurodegenerative disorders, as well as related research based on bionic olfactory sensing technology. This article mainly introduces the recent research progress of several commonly used objective olfactory tests and provides reference for more accurate evaluation of olfactory function.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Antidepressant activity of rose oxide essential oil: possible involvement of serotonergic transmission

Rose oxide (RO) is a monoterpene found in rose oil fragrances. This monoterpene has been reported to possess anti-inflammatory activity, however, little is known regarding its pharmacological activity. The present study was carried out to evaluate its antidepressant action and possible mechanisms of action. Analysis of ADMET pharmacokinetic properties (absorption, distribution, metabolism, excretion and toxicity) of rose oxide was performed by computational prediction analysis. Behavioral tests were performed to assess the interaction between rose oxide and the central nervous system and antidepressant effect that includes: forced swim test (FST), tail suspension test (TST), open field test (OFT) and rota-rod test. The results of pharmacokinetic and toxicological properties indicate that rose oxide could be used orally, since it has good intestinal absorption as well as pharmacological and toxicological properties that can be similar to pharmacological compounds (regular hepatic metabolism and low toxicity). Treatment with 50 mg/kg of rose oxide was able to decrease the immobility time of animals not affected by FST and TST and was not able to alter the motor activity of the OFT and rota-rod test, suggesting modulation and antidepressant activity. Docking data suggest that rose oxide can bind to receptors in the serotonergic pathway. The results described here suggest that rose oxide has antidepressant activity, modulating the serotonergic pathway.

Clinical assessment of olfactory function

Approximately 5% of the general population is affected by functional anosmia with approximately additional 15% exhibiting decreased olfactory function. Many of these individuals ask for help. Because the subjective rating of olfactory function is biased, assessment of olfactory function is important. Olfactory measurements are needed for patient counseling and the tracking of changes in the sense of smell over time. The present review provides an overview of frequently used psychophysical tests for olfactory function, discusses differences between threshold and suprathreshold aspects of olfactory function, and gives examples on how to apply psychophysical tests.

Mechanisms Linking Olfactory Impairment and Risk of Mortality

Olfaction is a sense involved in a complex set of tasks, influencing eating behavior, increasing awareness of environmental hazards and affecting social communication. Surprisingly, smell disorders are very frequent, especially in the elderly population. Several recent studies conducted mostly in older subjects have demonstrated a strong association between olfactory impairment and overall mortality risk, with anosmia being even more predictive of 5 years mortality risk than cardiovascular disease. Presently, the underlying pathophysiology linking olfactory impairment to mortality remains unknown and only putative mechanisms are suggested. This review aims to examine the link between olfactory impairment and mortality and to discuss existing ideas on underlying existing mechanisms including, (1) the effect of olfactory loss on nutrition, life-threatening situations and social interactions, (2) associated neurodegenerative diseases, (3) accelerated brain aging, and (4) reflection of general health status being reflected in olfactory function.

Difference of olfactory deficit in patients with acute episode of schizophrenia and major depressive episode

Aim Olfactory deficits are potential markers of early diagnosis, monitoring progress and predicting outcome in patients with schizophrenia and depression. We aimed to investigate differences in patterns and influencing factors of olfactory deficits between patients with acute episode of schizophrenia and major depressive episode (MDE).

METHODS

Fifty-two patients with acute episode of schizophrenia, 75 patients with unipolar MDE and 199 healthy controls were included in this retrospective study. Following a structured interview, participants underwent olfactory tests (Sniffin' Sticks), assessment of psychiatric symptoms (Positive and Negative Syndrome Scale), depressive symptoms (Hamilton Depression Rating Scale), and cognitive function (color-word test and word generation test).

RESULTS

Both patients with schizophrenia and MDE exhibited significant olfactory deficits, and MDE patients have poorer olfactory sensitivity than schizophrenia. Patients with MDE had a higher proportion of olfactory deficits (45.3% and 28%, respectively) but a better self-awareness (21.3% and 9.6%, respectively) than patients with schizophrenia. In patients with schizophrenia, PANSS scores was positively associated with olfactory sensitivity but negatively associated with olfactory identification, and olfactory discrimination was associated with word generation. In patients with MDE, olfactory discrimination was associated with word generation and age, but not disease severity. First-episode schizophrenia group showed significantly lower threshold scores than recurrent schizophrenia group, and first-episode MDE group had significantly lower threshold scores and higher discrimination scores than the recurrent MDE group.

CONCLUSIONS

Patterns and modulating factors of olfactory deficits in acute episode of schizophrenia and MDE are different, their differences should be considered when using olfactory deficits as marker in clinical practice.

When to collect resting-state data: The influence of odor on post-task resting-state connectivity

The human brain networks at rest represent spontaneous activity that is highly correlated between different brain regions. Previous studies have shown that these resting-state networks are flexible and dynamic, and they can be affected by performance of different types of tasks. Moreover, it has been suggested that the re-activation of a task-related brain network during rest promotes learning and improves the expertise on that task. However, it is still unclear whether the presence of different sensory information in the on-task state affects functional connectivity in subsequent resting-state fMRI even though the perception of the sensory information did not induce significant behavioral effects. To clarify this issue, we compared pre- and post-task resting-state fMRI of two groups of participants performing the same task either with an odor context (ODOR group) or without an odor context (AIR group). Seed-based functional connectivity analyses were performed with orbitofrontal cortex, piriform cortex and working-memory core network as seeds. The results showed that an odor context presented during an encoding task induced significant changes in the functional connectivity only within the olfactory network of the post-task resting-state compared to the same post-task situation without previous odor context. No significant difference in functional connectivity were found for the working-memory core network. This evidence emphasizes how the sensory context, in which a task is performed, is relevant for understanding the observed changes of functional connectivity during rest.