Olfactory Capacity Research Articles

The Domestication of Wild Boar Could Result in a Relaxed Selection for Maintaining Olfactory Capacity.

Domesticated animals are artificially selected to exhibit desirable traits, however not all traits of domesticated animals are the result of deliberate selection. Loss of olfactory capacity in the domesticated pig (Sus scrofa domesticus) is one example. We used whole transcriptome analysis (RNA-Seq) to compare patterns of gene expression in the olfactory mucosa of the pig and two subspecies of wild boar (Sus scrofa), and investigate candidate genes that could be responsible for the loss of olfactory capacity. We identified hundreds of genes with reductions in transcript abundance in pig relative to wild boar as well as differences between the two subspecies of wild boar. These differences were detected mainly in genes involved in the formation and motility of villi, cilia and microtubules, functions associated with olfaction. In addition, differences were found in the abundances of transcripts of genes related to immune defenses, with the highest levels in continental wild boar subspecies. Overall, the loss of olfactory capacity in pigs appears to have been accompanied by reductions in the expression of candidate genes for olfaction. These changes could have resulted from unintentional selection for reduced olfactory capacity, relaxed selection for maintaining olfactory capacity, pleiotropic effects of genes under selection, or other non-selective processes. Our findings could be a cornerstone for future researches on wild boars, pigs, feral populations, and their evolutionary trajectories, aimed to provide tools to better calibrate species management as well as guidelines for breeders.

Species-specific variation in mental gland secretions of turtles revealed by proteomic and lipidomic profiling

Chemical signaling through pheromones is an ancient and widespread mode of communication. Turtles and tortoises (chelonians) secrete pheromones via mental (chin) glands and have superior olfactory capacities rendering them a promising group to study the evolution and function of chemical communication in vertebrates. Here, we use state-of-the art proteomics and lipidomics techniques to identify and explore the possible functions of proteins and lipids secreted by mental glands in turtles. We examined four turtle species all from the family Geoemydidae, to understand among-species as well as sexual variation in the composition of mental gland secretions. Differential expression of a relatively small number (ca. 65) of proteins explained a large portion of the proteome variation across species, highlighting the existence of specific signals evolving even in closely related species. Lipidomic analysis revealed high inter-individual variation, but species differences could be attributed to five different lipid classes. The lipids found in mental glands could have a dietary origin or be related to individual condition, but may nonetheless be used in communication. We also examined sex-specific differences in the proteome of a single species (Mauremys leprosa) and found that males expressed a much larger array of proteins than females. Our findings establish a group of candidate proteins potentially involved in chemical signaling in freshwater geoemydid turtles. Alternatively, differently expressed proteins in mental glands could have an indirect link to chemical communication, being involved in pheromone transport and/or antioxidant protection.

The Olfactory Working Memory Capacity Paradigm.

Working memory capacity (WMC), a crucial component of working memory (WM), has consistently drawn the attention of researchers. Exploring the underlying neurobiological mechanisms behind it is currently a prominent focus in the field of neuroscience. Previously, we developed a novel behavioral paradigm for rodents called the olfactory working memory capacity (OWMC) paradigm, which serves as an effective tool for quantifying the WMC of rodents. The OWMC task comprises five phases: context adaptation, digging training, rule-learning for nonmatching to a single sample odor (NMSS), rule-learning for nonmatching to multiple sample odors (NMMS), and capacity testing. In the first phase, mice are handled to reduce stress and acclimate to the training cage. The second phase involves training mice to dig in a bowl of unscented sawdust to locate a piece of cheese. In the third phase, mice are trained to locate the cheese pellet in a bowl with a noveal odor. The fourth phase requires mice to distinguish the novel odor among multiple scented bowls to locate the cheese pellet. Finally, in the fifth phase, mice undergo several WMC tests until they achieve a stable level of performance. In this protocol paper, we will provide detailed instructions on how to implement the behavioral paradigm. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Context adaptation Basic Protocol 2: Digging training Basic Protocol 3: Rule-learning for NMSS Basic Protocol 4: Rule-learning for NMMS Basic Protocol 5: Capacity testing.

Prevalence and Magnitude of Olfactory Dysfunction in Allergic Rhinitis.

Although allergic rhinitis (AR) can negatively impact the ability to smell, the degree to which this occurs is not clear and prevalence estimates vary among studies. This study had 4 main objectives: (1) To estimate the prevalence and the degree of olfactory dysfunction in AR patients; (2) To compare olfactory perception between AR patients with different persistence and severity of symptoms and determine if olfactory testing may aid in differentiating among Allergic Rhinitis and its Impact on Asthma (ARIA) groups; (3) To determine whether allergic reactions to different allergens differentially impact olfactory function, and (4) Verify possible changes in the olfactory epithelium (OE) caused by AR. One hundred thirty-three patients with AR and one hundred controls were tested. The main outcome was the score in University of Pennsylvania Smell Identification Test (UPSIT®). The OE was examined using immunofluorescence markers for neuronal activity, apoptosis, oxidative stress, signal transduction, eosinophils, and epithelial thickness. Prevalence of olfactory dysfunction in the AR patients was higher (AR: 42.9% vs controls: 9%, P < .001). No difference was found either between intermittent and persistent disease cases (P = .58) or between cases with mild and those with moderate/severe symptomatology (P = .33). Lower olfactory capacity was not associated with the reaction to more (P = .48) or diverse types of allergens (Ps > .05). Although not significant, patients with AR had a greater amount of eosinophilia and a lower amount of cAMP (cyclic adenosine monophosphate) in the OE. The study highlights a higher prevalence of olfactory dysfunction in AR patients compared to controls, but olfactory testing may not effectively differentiate AR severity or allergen sensitivities. Although trends suggest potential pathophysiological changes in the OE of AR patients, further research is needed to validate these findings.

Toxicity evaluation of novel imidacloprid nanoribbons, using somatic mutation and fitness indexes in Drosophila melanogaster

ABSTRACT Nanoribbons of imidacloprid, a systemic and chloronicotinyl insecticide, were successfully synthesized by laser-induced fragmentation/exfoliation of imidacloprid powders suspended in water, with widths ranging from 160 to 470 nm, lengths in the micron scale, and thickness of a few atoms layers. The aim of the present study was to examine the effects of acute and chronic exposure to imidacloprid (IMC) bulk and compare its effects with synthesized imidacloprid nanoribbons (IMCNR) on larval and adult viability, developmental time, olfactory capacity, longevity, productivity, and genotoxicity in Drosophila melanogaster. Larvae or adults were exposed at 0.01, 0.02, or 0.03 ppm to IMC or IMCNR. Results demonstrated that IMCNR produced a significant reduction in viability and olfactory ability. IMC did not significantly alter viability and olfactory ability. Similarly, marked differences on longevity were detected between treatment with IMC and IMCNR where the lifespan of males treated with IMC was significantly higher than control while IMCNR produced a reduction. As for productivity, developmental time, and genotoxicity, no marked differences were found between both forms of IMC.

Early corticosteroid treatment enhances recovery from SARS-CoV-2 induced loss of smell in hamster

Among the numerous long COVID symptoms, olfactory dysfunction persists in ∼10 % of patients suffering from SARS-CoV-2 induced anosmia. Among the few potential therapies, corticoid treatment has been used for its anti-inflammatory effect with mixed success in patients. In this study, we explored its impact using hamster as an animal model. SARS-CoV-2 infected hamsters lose their smell abilities and this loss is correlated with damage of the olfactory epithelium and persistent presence of innate immunity cells. We started a dexamethasone treatment 2 days post infection, when olfaction was already impacted, until 11 days post infection when it started to recover. We observed an improvement of olfactory capacities in the animals treated with corticoid compared to those treated with vehicle. This recovery was not related to differences in the remaining damage to the olfactory epithelium, which was similar in both groups. This improvement was however correlated with a reduced inflammation in the olfactory epithelium with a local increase of the mature olfactory neuron population. Surprisingly, at 11 days post infection, we observed an increased and disorganized presence of immature olfactory neurons, especially in persistent inflammatory zones of the epithelium. This unusual population of immature olfactory neurons coincided with a strong increase of olfactory epithelium proliferation in both groups. Our results indicate that persistent inflammation of the olfactory epithelium following SARS-CoV-2 infection may alter the extent and speed of regeneration of the olfactory neuron population, and that corticoid treatment is effective to limit inflammation and improve olfaction recovery following SARS-CoV-2 infection.

Avialan-like brain morphology in Sinovenator (Troodontidae, Theropoda)

Many modifications to the skull and brain anatomy occurred along the lineage encompassing non-avialan theropod dinosaurs and modern birds. Anatomical changes to the endocranium include an enlarged endocranial cavity, relatively larger optic lobes that imply elevated visual acuity, and proportionately smaller olfactory bulbs that suggest reduced olfactory capacity. Here, we use micro-computed tomographic (μCT) imaging to reconstruct the endocranium and its neuroanatomical features from an exceptionally well-preserved skull of Sinovenator changii (Troodontidae, Theropoda). While its overall morphology resembles the typical endocranium of other troodontids, Sinovenator also exhibits unique endocranial features that are similar to other paravian taxa and non-maniraptoran theropods. Landmark-based geometric morphometric analysis on endocranial shape of non-avialan and avialan dinosaurs points to the overall brain morphology of Sinovenator most closely resembling that of Archaeopteryx, thus indicating acquisition of avialan-grade brain morphology in troodontids and wide existence of such architecture in Maniraptora.

Behavioural evidence for enhanced olfactory and trigeminal perception in congenital hearing loss.

Sensory deprivation, especially hearing loss (HL), offers a valuable model for studying neuroplasticity in the human brain and adaptive behaviours that support the daily lives of those with limited or absent sensory input. The study of olfactory function is particularly important as it is an understudied aspect of sensory deprivation. This study aimed to compare the effects of congenital HL on olfactory capacity by using psychophysical tasks. Methodological concerns from previous studies regarding the onset of HL and cognitive assessments were addressed. We recruited 11 individuals with severe-to-profound sensorineural HL (SNHL) since birth and 11 age- and sex-matched typical hearing non-signers. We used standardized neuropsychological tests to assess typical cognition among participants with SNHL. We evaluated olfactory functions by assessing olfactory detection threshold, odour discrimination and odour identification. Hearing-impaired participants outperformed their typical hearing counterparts in olfactory tasks. We further evaluated the accuracy and response time in identifying and localizing odours to disentangle olfactory sensitivity from trigeminal system sensitivity. Participants with SNHL demonstrated higher sensitivity to both the identification and localization tasks. These findings suggest that congenital SNHL is associated with enhanced higher-level olfactory processing and increased trigeminal sensitivity.

The olfactory working memory capacity paradigm: A more sensitive and robust method of assessing cognitive function in male 5XFAD mice.

The olfactory working memory capacity (OWMC) paradigm is able to detect cognitive deficits in 5XFAD mice (an animal model of Alzheimer's disease [TG]) as early as 3 months of age, while other behavioral paradigms detect cognitive deficits only at 4-5 months of age. Therefore, we aimed to demonstrate that the OWMC paradigm is more sensitive and consistent in the early detection of declines in cognitive function than other commonly used behavioral paradigms. The prefrontal cortex (PFC), retrosplenial cortex (RSC), subiculum (SUB), and amygdala (AMY) of 5XFAD mice were harvested and subjected to immunostaining to detect the expression of β-amyloid (Aβ). Additionally, we compared the performance of 3-month-old male 5XFAD mice on common behavioral paradigms for assessing cognitive function (i.e., the open field [OF] test, novel object recognition [NOR] test, novel object location [NOL] test, Y-maze, and Morris water maze [MWM]) with that on the OWMC task. In the testing phase of the OWMC task, we varied the delay periods to evaluate the working memory capacity (WMC) of wild-type (WT) mice. Significant amyloid plaque deposition was observed in the PFC, RSC, SUB, and AMY of 3-month-old male 5XFAD mice. However, aside from the OWMC task, the other behavioral tests failed to detect cognitive deficits in 5XFAD mice. Additionally, to demonstrate the efficacy of the OWMC task in assessing WMC, we varied the retention delay periods; we found that the WMC of WT mice decreased with longer delay periods. The OWMC task is a sensitive and robust behavioral assay for detecting changes in cognitive function.

Ozone exposure induces metabolic stress and olfactory memory disturbance in honey bees.

Human activities, urbanization, and industrialization contribute to pollution that affects climate and air quality. A main atmospheric pollutant, the tropospheric ozone (O3), can damage living organisms by generating oxidative radicals, causing respiratory problems in humans and reducing yields and growth in plants. Exposure to high concentrations of O3 can result in oxidative stress in plants and animals, eventually leading to substantial ecological consequences. Plants produce volatile organic compounds (VOCs) emitted in the environment and detected by pollinators (mainly by their antennae), foraging for nutritious resources. Several pollinators, including honey bees, recognize and discriminate flowers through olfactory cues and memory. Exposure to different concentrations of O3 was shown to alter the emission of floral VOCs by plants as well as their lifetime in the atmosphere, potentially impacting plant-pollinator interactions. In this report, we assessed the impacts of exposure to field-realistic concentrations of O3 on honey bees' antennal response to floral VOCs, on their olfactory recall and discriminative capacity and on their antioxidant responses. Antennal activity is altered depending on VOCs structure and O3 concentrations. During the behavioral tests, we first check consistency between olfactory learning rates and memory scores after 15 min. Then bees exposed to 120 and 200 ppb of ozone do not exert specific recall responses with rewarded VOCs 90 min after learning, compared to controls whose specific recall responses were consistent between time points. We also report for the first time in honey bees how the superoxide dismutase enzyme, an antioxidant defense against oxidative stress, saw its enzymatic activity rate decreases after exposure to 80 ppb of ozone. This work tends to demonstrate how hurtful can be the impact of air pollutants upon pollinators themselves and how this type of pollution needs to be addressed in future studies aiming at characterizing plant-insect interactions more accurately.

Diminished activation of excitatory neurons in the prelimbic cortex leads to impaired working memory capacity in mice

BackgroundWorking memory capacity impairment is an early sign of Alzheimer's disease, but the underlying mechanisms remain unclear. Clarifying how working memory capacity is affected will help us better understand the pathological mechanism of Alzheimer's disease. We used the olfactory working memory capacity paradigm to evaluate memory capacity in 3-month-old 5XFAD (an animal model of Alzheimer's disease) mice. Immunofluorescence staining of the prefrontal cortex was performed to detect the number of FOS-positive neurons, calmodulin-dependent protein kinase II-positive neurons, and glutamate decarboxylase-positive neurons in the prelimbic cortex and infralimbic cortex. A chemogenetic method was then used to modulate the inhibition and activation of excitatory neurons in the prelimbic cortex of wild-type and 5XFAD mice and to measure the memory capacity of mice.ResultsWorking memory capacity was significantly diminished in 5XFAD mice compared to littermate wild-type mice. Neuronal activation of the prelimbic cortex, but not the infralimbic cortex, was attenuated in 5XFAD mice performing the olfactory working memory capacity task. Subsequently, the FOS-positive neurons were co-localized with both calmodulin-dependent protein kinase II-positive neurons and glutamate decarboxylase-positive neurons. The results showed that the activation of excitatory neurons in the prelimbic cortex was correlated with working memory capacity in mice. Our results further demonstrate that the chemogenetic inhibition of prelimbic cortex excitatory neurons resulted in reduced working memory capacity in wild-type mice, while the chemogenetic activation of prelimbic cortex excitatory neurons improved the working memory capacity of 5XFAD mice.ConclusionThe diminished activation of prelimbic cortex excitatory neurons in 5XFAD mice during task performance is associated with reduced working memory capacity, and activation modulation of excitatory neurons by chemogenetic methods can improve memory capacity impairment in 5XFAD mice. These findings may provide a new direction for exploring Alzheimer's disease therapeutic approaches.

Pig olfaction: the potential impact and use of odors in commercial pig husbandry

Pigs are widely acknowledged for their olfactory abilities. Research on pigs’ olfactory capacities has focused mainly on aspects of olfaction that directly impact production, such as palatability of feed and pheromones to stimulate reproduction. Several basic research questions remain unanswered, such as which odors do pigs like/dislike, and how may odors enrich their lives? This review aims to explore the currently available literature on pig olfaction to elucidate the current knowns and unknowns within the following topics: chemicals in a pig’s environment, the olfactory organs of pigs, olfactory detection and acuity, behavioral reactions to odors, aversive odors, reaction to novel odors, attractive odors, and odors as a management tool in commercial pig production. The review focuses on complex odors of non-social origin (e.g., ammonia), and when information on this topic is lacking we include information from research on other mammalian species. We found that the olfactory organs of pigs are already functional at birth and that piglets can recognize the smell of the sow within 12h postpartum. Compared with humans and several other mammalian species, the pig’s olfactory system is highly developed, and the use of their sense of smell is incorporated into their natural behavior. While sniffing is a well-known behavior in pigs’ exploratory behavioral repertoire, this review points to a lack of knowledge on pigs’ behavioral reactions specifically when exposed to odors. Some odors appear attractive to pigs, whereas others appear repellent. Depending on the properties of the odor, providing pigs access to odors may be a way to stimulate their sense of smell, and could possibly be used in commercial pig production to enrich their lives. The review lastly highlights potential risks for animal welfare caused from lacking knowledge about how pigs perceive odors in their environment, and proposes future research questions and ways to utilize pigs’ sense of smell in the daily management of these animals. Further research on the olfactory abilities of pigs could help to ensure a more sustainable pig production.

Genotoxic action of bifenthrin nanoparticles and its effect on the development, productivity, and behavior of Drosophila melanogaster

ABSTRACT Rapid development of nanotechnology, particularly nanoparticles of pesticides, has facilitated the transformation of traditional agriculture. However, testing their effectiveness is essential for avoiding any environmental or adverse human health risk attributed to nanoparticle-based formulations, especially insecticides. Recently, organic nanoparticles of bifenthrin, a pyrethroid insecticide, were successfully synthesized by laser ablation of solids in liquid technique, with the most probable size of 5 nm. The aim of the present study was to examine the effects of acute exposure to bifenthrin (BIF) or bifenthrin nanoparticles (BIFNP) on larval-adult viability, developmental time, olfactory capacity, longevity, productivity defined as the number of eggs per couple, and genotoxicity in Drosophila melanogaster. Data demonstrated that BIFNP produced a marked delay in developmental time, significant reduction in viability and olfactory ability compared to BIF. No marked differences were detected between BIF and BIFNP on longevity and productivity. Genotoxicity findings indicated that only BIF, at longer exposure duration increased genetic damage.

Menstrual cycle-modulated intrinsic connectivity enhances olfactory performance during periovulatory period.

Olfactory capacity increases during the period of ovulation, perhaps as an adjunct to mate selection; however, researchers have yet to elucidate the neural underpinning of menstrual cycle-dependent variations in olfactory performance. A cohort of healthy volunteers (n = 88, grand cohort) underwent testing for gonadal hormone levels and resting-state functional magnetic resonance imaging with a focus on intrinsic functional connectivity (FC) in the olfactory network based on a priori seeds (piriform cortex and orbitofrontal cortex) during the periovulatory (POV) and menstrual (MEN) phases. A subcohort (n = 20, olfaction cohort) returned to the lab to undergo testing of olfactory performance during the POV and MEN phases of a subsequent menstrual cycle. Olfactory performance and FC were both stronger in the periovulatory phase than in the menstrual phase. Enhanced FC was observed in the network targeting the cerebellum in both the grand and olfaction cohorts, while enhanced FC was observed in the middle temporal gyrus, lingual gyrus, dorsal medial prefrontal cortex, and postcentral gyrus in the grand cohort. Periovulatory progesterone levels in the grand cohort were positively correlated with FC in the network targeting the insula and paracentral lobule. Our analysis revealed that superior olfactory function in the periovulatory period is associated with enhanced intrinsic connectivity in the olfactory network. These findings can be appreciated in the context of evolutionary biology.

Olfaction unraveled: Anatomy, dysfunctions and implications for health and sensory perception

This review addresses the fundamental role of smell in human life, including its function in detecting odors, influencing personal preferences, and social behaviors. The article discusses the anatomy of the olfactory system, covering the structures involved in olfactory detection and processing. The evaluation of olfactory function is explored using different approaches, such as standardized tests, clinical examinations, and imaging techniques, which allow an accurate assessment of olfactory capacity and assist in the diagnosis of olfactory-related disorders. Additionally, conditions such as anosmia and dysosmia are addressed, investigating their causes, impacts, and diagnostic methods. Anosmia may be due to lesions in the olfactory structures or underlying medical conditions, while dysosmias involve qualitative alterations in the perception of smell. The article also discusses the prevalence of olfactory alterations in different contexts, including the COVID-19 pandemic, which has shown association with temporary or persistent loss of smell. Finally, the importance of advancing research in this area for a thorough understanding of the pathophysiology of olfactory alterations is emphasized. This understanding is critical for the development of personalized and effective therapeutic strategies. Collaboration between researchers and healthcare professionals is essential to drive scientific and clinical advances related to this topic. It is hoped that this review will provide a comprehensive overview of olfaction, contributing to a better understanding of olfactory mechanisms and supporting more effective clinical approaches to the diagnosis and treatment of olfactory disorders.

Resistance to deltamethrin in Triatoma infestans (Hemiptera: Reduviidae): Does it influence the phenotype of antennae, wings, and heads?

In vector control terms, insecticide resistance is the development of the capacity, of an insect population, to tolerate doses of an insecticide that are lethal to most individuals in a typical population of the same species. The genetic changes that determine resistance may have adaptive costs in the resistant phenotype or, conversely, may result in an adaptive advantage when compared to susceptible insects in the environment without insecticides. Triatoma infestans is one of the main vectors of Trypanosoma cruzi in the southern cone of South America.High insecticide resistance in T. infestans was detected in Argentina in Salta and Chaco provinces. The objective of this study was to determine the possible morphometric changes in wings, heads, and the antennal phenotype of deltamethrin-resistant T. infestans (RR) males and females compared to susceptible insects (SS), evaluating its implication in adaptive processes such as olfactory capacity, dispersion, and probability of colonizing new habitats, among others. Nine type I landmarks were marked on wings, 5 type II landmarks on heads, and 10 antennal sensilla were counted on 106 adults of both sexes (resistant and susceptible from first and second laboratory generations). Morphological divergence was observed between the two groups (RR and SS). The RR insects showed smaller sizes of wings and heads and shape compatible with lower dispersal potential and different active dispersal behaviors. Antennae also revealed sensory simplification in RR and divergence between RR and SS, although more marked in females. This study characterizes for the first time T. infestans RR and SS through wings, heads, and antennae. The results suggest a lower dispersive potential in resistant insects and the differences described lay the foundations for the identification of a resistance biomarker in triatomines.

Global olfactory function correlates with global sexual functioning in men and women.

Olfaction is intimately involved in reproductive behaviors. However, there is limited evidence about the relationship between olfactory and sexual functioning, and whether this relationship is modulated by gender. This study aimed to investigate the correlates between olfactory and sexual functioning in a cohort of young healthy individuals; secondary outcomes were the possible correlates between disgust and perceived vulnerability to illness, with particular relation to sexual attitudes. Between January 2019 and December 2022, we enrolled 125 participants (51 males and 74 females) without known sexual disorders. The mean age was 28.47±8.6, and the mean Body Mass Index (BMI) was 23.86±3.3 without major disease or concomitant drug assumption, except for nutraceutical use. Olfactory sensitivity was tested with the Sniffin' Sticks Test (SST). Body Odor Disgust Scale (BODS) and Perceived Vulnerability to Disease (PVD) questionnaires were administered for the evaluation of perceived susceptibility to illness along with the Sexual Attitude Scale (SAS) for the evaluation of sexual attitudes. Sexual function was evaluated by the Female Sexual Function Index (FSFI) and International Index of Erectile Function (IIEF) questionnaires, respectively. Overall, a close relationship between sexual function and olfaction in both sexes (P<0.05) was found. In the male sample, better olfactive scores were positively correlated to all IIEF sub-domains but negatively with BMI and age, respectively (P<0.05). Moreover, olfaction was negatively correlated with a restrictive attitude towards sexuality (SAS) (P<0.05). The latter was also positively correlated with PVD (P<0.01). In the female sample, all FSFI subscales but sexual desire was positively correlated with olfaction (P<0.05). We herein confirm that olfactory capacities positively correlate with sexual behavior in both sexes. In males, these findings were mostly dependent upon increasing age and BMI. In females all domains of sexual function but sexual desire correlated with olfactory capacity, thus suggesting independent neural pathway activation for sexual desire. Finally, better olfactory capacities seem to determine sexual attitudes and disease avoidance behaviors irrespective of gender.

Could olfactory identification be a prognostic factor in detecting cognitive impairment risk in the elderly?

Aging contributes to the deterioration of the olfactory system in humans. Several studies indicate that the olfactory identification test alone may function as a screening test for olfactory dysfunction and they are more feasible to apply in clinical practice. Olfactory identification may be a predictor for cognitive impairment. Multiple studies have considered the use of odor identification as a measure to identify the conversion from normality to mild cognitive impairment or dementia. The objectives were (i) to elucidate the associations between cognitive status and olfactory identification performance in aging; (ii) understand the predictive value of olfactory capacity in identifying subjects with cognitive impairment risk; and (iii) to study how cognitive status and olfactory identification relate with other variables of wellness in aging, such as functional capabilities and clinical measures. For this purpose, a group of 149 participants (77.15 ± 7.29 years; 73 women of 76.7 ± 8 years and 76 men of 77.6 ± 6.52 years) were recruited and were subjected to a sociodemographic questionnaire, a psychological screening tool of general cognitive status, an olfactory identification evaluation, and clinical measures. The participants were divided into groups based on their cutoff scores of previous scientific reports about the Spanish version of Montreal Cognitive Assessment. Our results indicate an age-associated decline in olfactory identification ability and intensity of odor perception. The predictive ability of olfactory identification scores for the risk of mild and severe impairment is around 80%. Olfactory identification decreases with cognitive function. Performance in odor identification is associated with impairment of episodic memory and executive functions. These findings further our current understanding of the association between cognition and olfaction, and support olfactory assessment in screening those at higher risk of dementia.

The eNOS isoform exhibits increased expression and activation in the main olfactory bulb of nNOS knock-out mice.

The main olfactory bulb (MOB) is a neural structure that processes olfactory information. Among the neurotransmitters present in the MOB, nitric oxide (NO) is particularly relevant as it performs a wide variety of functions. In this structure, NO is produced mainly by neuronal nitric oxide synthase (nNOS) but also by inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). The MOB is considered a region with great plasticity and the different NOS also show great plasticity. Therefore, it could be considered that this plasticity could compensate for various dysfunctional and pathological alterations. We examined the possible plasticity of iNOS and eNOS in the MOB in the absence of nNOS. For this, wild-type and nNOS knock-out (nNOS-KO) mice were used. We assessed whether the absence of nNOS expression could affect the olfactory capacity of mice, followed by the analysis of the expression and distribution of the NOS isoforms using qPCR and immunofluorescence. NO production in MOB was examined using both the Griess and histochemical NADPH-diaphorase reactions. The results indicate nNOS-KO mice have reduced olfactory capacity. We observed that in the nNOS-KO animal, there is an increase both in the expression of eNOS and NADPH-diaphorase, but no apparent change in the level of NO generated in the MOB. It can be concluded that the level of eNOS in the MOB of nNOS-KO is related to the maintenance of normal levels of NO. Therefore, our findings suggest that nNOS could be essential for the proper functioning of the olfactory system.

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.