Olfactory Nomenclature: An Orchestrated Effort to Clarify Terms and Definitions of Dysosmia, Anosmia, Hyposmia, Normosmia, Hyperosmia, Olfactory Intolerance, Parosmia, and Phantosmia/Olfactory Hallucination.

BACKGROUND: Definitions are essential for effective communication and discourse, particularly in science. They allow the shared understanding of a thought or idea, generalization of knowledge, and comparison across scientific investigation. The current terms describing olfactory dysfunction are vague and overlapping. SUMMARY: As a group of clinical olfactory researchers, we propose the standardization of the terms "dysosmia," "anosmia," "hyposmia," "normosmia," "hyperosmia," "olfactory intolerance," "parosmia," and "phantosmia" (or "olfactory hallucination") in olfaction-related communication, with specific definitions in this text. KEY MESSAGES: The words included in this paper were determined as those which are most frequently used in the context of olfactory function and dysfunction, in both clinical and research settings. Despite widespread use in publications, however, there still exists some disagreement in the literature regarding the definitions of terms related to olfaction. Multiple overlapping and imprecise terms that are currently in use are confusing and hinder clarity and universal understanding of these concepts. There is a pressing need to have a unified agreement on the definitions of these olfactory terms by researchers working in the field of chemosensory sciences. With the increased interest in olfaction, precise use of these terms will improve the ability to integrate and advance knowledge in this field.

Relationship Between Olfactory Disturbance After Acute Ischemic Stroke and Latent Thalamic Hypoperfusion.

Odor detection, recognition, and identification were assessed in 19 acute ischemic stroke patients who had no magnetic resonance imaging-detectable thalamic lesions but in whom technetium-99m ethyl cysteinate dimer single photon emission tomography revealed thalamic hypoperfusion. Although these patients were unaware of reduced olfactory function, they exhibited significantly lower scores in tests for odor identification and recognition threshold as compared with 9 ischemic stroke controls that had normal thalamic hypoperfusion. However, absolute odor detection thresholds were similar in the 2 groups. These results demonstrate the usefulness of cerebral perfusion scintigraphy in assessing sensory loss after ischemic stroke and provide further evidence for the role of the thalamus in olfaction.

The Impact of Ovariectomy on Olfactory Neuron Regeneration in Mice.

Estrogen has been shown to affect differentiation and proliferation as a mitogen in various neural systems. Olfactory receptor cells are unique within the nervous system, and have the ability to regenerate even after an individual has reached maturity. Olfactory receptor cells also regenerate after experimentally induced degeneration. The purpose of this study is to observe the influence of estrogen depletion induced by ovariectomy on olfactory nerve regeneration. Female mice underwent bilateral ovariectomy at 8 weeks of age and received intraperitoneal administration of methimazole 1 week later. At 2, 4, and 6 weeks after methimazole administration, the olfactory mucosa was analyzed histochemically to determine olfactory epithelium (OE) thickness, olfactory marker protein distribution, and Ki-67 immunoreactivity. Furthermore, 2 weeks after ovariectomy, trkA protein distribution in the OE and nerve growth factor (NGF) levels in the olfactory bulb were determined by immunohistochemistry and enzyme-linked immunosorbent assay, respectively. Our results showed that in ovariectomized mice OMP, Ki-67, and trkA-immunopositive cells expression decreased at 2 weeks after methimazole injection, a time point at which regeneration is underway. At this same time point, although NGF production in the olfactory bulb had increased before methimazole administration, no differences were observed between the ovx and control groups. These results suggest that estrogen depletion induces a suppressive effect on regeneration of olfactory neurons, and that estrogen may have a potential use in the treatment of sensorineural olfactory dysfunction.

Effects of Tokishakuyakusan on Regeneration of Murine Olfactory Neurons In Vivo and In Vitro.

Post-upper respiratory tract infection related olfactory dysfunction typically occurs due to neural damage after an upper respiratory tract infection associated with a common cold or influenza. At present, Tokishakuyakusan, a Japanese traditional Kampo medicine, has been found to be effective for post-viral olfactory dysfunction. However, the pharmacodynamics of Tokishakuyakusan in the treatment of post-viral olfactory dysfunction remains unresolved. We investigated the effects of Tokishakuyakusan on the regeneration of olfactory neurons and expression of nerve growth factor (NGF) in neural systems, using in vivo murine studies and in vitro cell culture studies. Eight-week-old BALB/C female mice were fed a pellet diet with or without Tokishakuyakusan. Degeneration of cells in olfactory epithelium was induced by intraperitoneal methimazole injection. Regeneration of olfactory neurons was observed by histological and immunohistochemical procedures. NGF expression in the olfactory bulb was measured by enzyme-linked immunosorbent assay. NGF gene and protein expression were measured using rat primary cultured astrocytes by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. We found that olfactory marker protein, Ki-67, and NGF were more highly expressed in the olfactory epithelium during the regeneration period in mice receiving Tokishakuyakusan. In cultured astrocytes, Tokishakuyakusan as well as its individual components, Atractylodes lancea rhizome and Japanese angelica root, increased NGF expression. Screening assays revealed that NGF production was increased by atractylodin and levistolide A, which are ingredients in Atractylodes lancea rhizome and Japanese angelica root, respectively. These results suggest that Tokishakuyakusan promotes regeneration of olfactory neurons by increasing NGF expression in the olfactory bulb.

Reduced nasal transport of insulin-like growth factor-1 to the mouse cerebrum with olfactory bulb resection.

Although the olfactory nerve is involved in nasal transport of insulin-like growth factor-1 (IGF-1) to the brain, to our knowledge there have been no direct assessments of the effects of olfactory nerve damage on this transport. To determine whether olfactory bulb resection resulted in reduced transport of nasally administered human recombinant IGF-1 (hIGF-1) to the cerebrum, we measured the uptake of nasally administered iodine-125 hIGF-1 ((125)I-hIGF-1) in the cerebrum as a percentage of that in the blood in male ICR mice subjected to left olfactory bulb resection (model mice) and in sham-operated male ICR mice (control mice). Phosphorylated extracellular signal-regulated kinase (ERK) 1/2 (Thr202/Tyr204)/(Thr185/Tyr187) as a percentage of total ERK 1/2 in the left cerebrum was also assessed by using enzyme-linked immunosorbent assay after nasal administration of hIGF-1. Uptake of nasally administered (125)I-hIGF-1 in the cerebrum as a percentage of that in the blood was significantly lower in the model group than in the control group 30min after nasal administration of hIGF-1. Unilateral olfactory bulb resection prevented nasally administered hIGF-1 from increasing the phosphorylation of ERK 1/2 in the mouse cerebrum in vivo. These findings suggest that olfactory bulb damage reduces nasal transport of hIGF-1 to the brain in vivo.

Histological changes in the olfactory bulb and rostral migratory stream due to interruption of olfactory input.

OBJECTIVE: Periglomerular and granule cells in the adult mammalian olfactory bulb modulate olfactory signal transmission. These cells originate from the subventricular zone, migrate to the olfactory bulb via the Rostral Migratory Stream (RMS), and differentiate into mature cells within the olfactory bulb throughout postnatal life. While the regulation of neuroblast development is known to be affected by external stimuli, there is a lack of information concerning changes that occur during the recovery process after injury caused by external stimuli. To address this gap in research, the present study conducted histological observations to investigate changes in the olfactory bulb and RMS occurring after the degeneration and regeneration of olfactory neurons. METHODS: To create a model of olfactory neurodegeneration, adult mice were administered methimazole intraperitoneally. Nasal tissue and whole brains were removed 3, 7, 14 and 28 days after methimazole administration, and EdU was administered 2 and 4 h before removal of these tissues to monitor dividing cells in the RMS. Methimazole-untreated mice were used as controls. Olfactory nerve fibers entering the olfactory glomerulus were observed immunohistochemically using anti-olfactory marker protein. In the brain tissue, the entire RMS was observed and the volume and total number of cells in the RMS were measured. In addition, the number of neuroblasts and dividing neuroblasts passing through the RMS were measured using anti-doublecortin and anti-EdU antibodies, respectively. Statistical analysis was performed using the Tukey test. RESULTS: Olfactory epithelium degenerated was observed after methimazole administration, and recovered after 28 days. In the olfactory glomeruli, degeneration of OMP fibers began after methimazole administration, and after day 14, OMP fibers were reduced or absent by day 28, and overall OMP positive fibers were less than 20%. Glomerular volume tended to decrease after methimazole administration and did not appear to recover, even 28 days after recovery of the olfactory epithelium. In the RMS, EdU-positive cells decreased on day 3 and began to increase on day 7. However, they did not recover to the same levels as the control methimazole-untreated mice even after 28 days. CONCLUSION: These results suggest that the division and maturation of neuroblasts migrating from the RMS was suppressed by olfactory nerve degeneration or the disruption of olfactory input.

Association of olfactory and gustatory function with memory among community-dwelling independent older adults.

Background: This study examined the association between memory function and reduced olfactory and gustatory function among independent community-dwelling older adults. Methods: This cross-sectional study included 127 older adults (65.4% women). We assessed their memory, odor, and taste identification skills. Open essence (OE) test and taste strips (TS) were used to identify hyposmia (OE test ≤6) and hypogeusia (TS test ≤8), respectively. Results: Participants with severe hyposmia had significantly poorer memory functions compared to participants without severe hyposmia. After adjusting for covariates, multivariate logistic regression models revealed a significant association between immediate recognition performance and a decreased likelihood of severe hyposmia (odds ratio = 0.65, 95% confidence interval = 0.47-0.90). We observed no significant association between taste function and memory. Conclusions: Memory function may be associated with olfactory impairment but not with gustatory function in older adults.

Evaluation of odor recognition threshold measurement methods in T&T olfactometry: A survey study.

OBJECTIVE: The odor recognition thresholds in T&T olfactometry are measured by either the examiner's judgment of the patients' odor expression for each standard odor or by the patient's choice of the correct response from an olfactory term table. This study aimed to clarify the correct odor expressions and use of the olfactory term table. METHODS: A questionnaire was administered to otolaryngologists or medical staff in charge of testing at facilities where T&T olfactometry is performed. The questionnaire consisted of the facility's background, environment and procedures of T&T olfactometry, choice of the correct answer with five different standard odors, and use of the olfactory term table. For the choices, the expressions used were those considered correct at Nippon Medical School Tama Nagayama Hospital and the Kyoto Nose and Allergy Clinic. RESULTS: A total of 81 valid responses were obtained. Most respondents belonged to medical and educational institutions (59.3%, 48/81). The laboratories in the respondents' institutions were completely ventilated using various methods. Clinical laboratory technicians inspected 51.7% (45/81) of the facilities. The order of standard odors in the odor recognition threshold test differs depending on the facility. When the examiner was unsure about the answer given by the patient in the odor recognition threshold test, 16.1% (9/56) of the respondents chose "present the olfactory term table," 33.9% (19/56) chose "increase the concentration," and 37.5% (21/56) chose "present the olfactory term table" or "increase the concentration," depending on the situation. A total of 96.4% (54/56) of the facilities treated odor expressions other than those in the olfactory term table as correct, and the odor expressions that were considered correct differed from facility to facility. Of the respondents, 80.2% (65/81) answered "I know the olfactory term table," and the mean value of satisfaction with the current olfactory term table was 4.4 ± 3.0. Of the respondents, 81.5% (53/65) answered that "the timing of presenting the olfactory term table should be standardized in all facilities." CONCLUSION: In the odor recognition threshold test by T&T olfactometry, this study revealed that the odor expressions considered as correct answers for the standard odors and the use of the olfactory term table differed among facilities.

Efficacy of tokishakuyakusan and mecobalamin on post-infectious olfactory dysfunction: A prospective multicenter study.

OBJECTIVE: To determine if tokishakuyakusan (TSS) is effective for treating post-infectious olfactory dysfunction (PIOD) compared with vitamin B12 (mecobalamin). METHODS: We conducted a randomized, nonblinded clinical trial. Patients with PIOD enrolled in 17 hospitals and clinics from 2016 to 2020 were randomly divided into two groups, and we administered TSS or mecobalamin for 24 weeks. Their olfactory function was examined using interviews and T&T olfactometry. The improvement of olfactory dysfunction was assessed following the criteria of the Japanese Rhinologic Society. RESULTS: Overall, 82 patients with PIOD were enrolled in this study. In the TSS and mecobalamin groups, 39 patients completed the medication regimen. In the TSS and mecobalamin groups, olfactory dysfunction was significantly improved based on self-reports and olfactory test results. The improvement rate of olfactory dysfunction was 56% in the TSS group and 59% in the mecobalamin group. Early intervention within 3 months produced a better prognosis than the treatment initiated after 4 months. Furthermore, age and sex differences were not observed. Both medications produced no severe adverse events. CONCLUSION: The present study showed that TSS and mecobalamin might be useful for treating PIOD.

[Assessment of treatment effect for acromegaly with sleep disordered breathing].

Acromegaly is caused by excessive secretion of growth hormone (GH) and presents with a variety of clinical manifestations, including facial disfigurement and abnormally large hands and feet, as well as diabetes mellitus, hypertension, and sleep-disordered breathing (SDB). Although SDB is known to be associated with serious symptoms, there have been few study reports, and no clear consensus has been reached regarding the method of assessment of individual treatments. We report herein on the results of surgical intervention with transsphenoidal surgery (TSS) for acromegaly and assessment of the treatment effect after the intervention. We studied 6 patients who received a diagnosis of acromegaly complicated with SDB and underwent TSS at our hospital. Polysomnography (PSG) was performed before and after TSS, and the polysomnograms were analyzed. We also examined changes in the levels of GH and insulin-like growth factor-1 (IGF-1) on blood biochemistry. In 6 cases of acromegaly with SDB, we were able to confirm endocrinologic improvement of TSS with blood biochemistry. However there was no meaningful improvement in the PSG index for SDB.

Olfactory Regeneration with Nasally Administered Murine Adipose-Derived Stem Cells in Olfactory Epithelium Damaged Mice.

In this study, we aimed to determine whether nasally administered murine adipose-derived stem cells (ADSCs) could support olfactory regeneration in vivo. Olfactory epithelium damage was induced in 8-week-old C57BL/6J male mice by intraperitoneal injection of methimazole. Seven days later, OriCell adipose-derived mesenchymal stem cells obtained from green fluorescent protein (GFP) transgenic C57BL/6 mice were nasally administered to the left nostril of these mice, and their innate odor aversion behavior to butyric acid was assessed. Mice showed significant recovery of odor aversion behavior, along with improved olfactory marker protein (OMP) expression on both sides of the upper-middle part of the nasal septal epithelium assessed by immunohistochemical staining 14 d after the treatment with ADSCs compared with vehicle control animals. Nerve growth factor (NGF) was detected in the ADSC culture supernatant, NGF was increased in the nasal epithelium of mice, and GFP-positive cells were observed on the surface of the left side nasal epithelium 24 h after left side nasal administration of ADSCs. The results of this study suggest that the regeneration of olfactory epithelium can be stimulated by nasally administered ADSCs secreting neurotrophic factors, thereby promoting the recovery of odor aversion behavior in vivo.

Sarcopenia and decline in appendicular skeletal muscle mass are associated with hypoperfusion in key hubs of central autonomic network on 3DSRT in older adults with progression of normal cognition to Alzheimer's disease.

AIM: Although sarcopenia is common in patients with Alzheimer's disease (AD), the neural substrates involved remain unclear. We investigated the relationship between sarcopenia, as well as its definition components, and regional cerebral blood flow (rCBF) in older adults with progression of normal cognition to AD. METHODS: 99m Tc-ethyl-cysteinate-dimer single-photon emission computed tomography was carried out in 95 older adults with progression of normal cognition to AD (40 men and 55 women, mean ± SD age 80.9 ± 6.8 years). The associations of rCBF determined by 3-D stereotactic region of interest template software, with sarcopenia and its definition components, slower gait speed, weaker grip strength, and decline in appendicular skeletal muscle mass index (ASMI) were analyzed. RESULTS: Logistic regression analysis adjusted by age, sex, mini-mental state examination score and education showed that sarcopenia as well as ASMI less than the cut-off (men 7.0 kg/m2 , women 5.7 kg/m2 ) were associated with significantly reduced rCBF in the key hub of the central autonomic network, including the insula, anterior cingulate cortex, subcallosal area, rectal gyrus, hypothalamus, amygdala and caudate head. Sarcopenia and ASMI decline were associated with hypoperfusion in the aforementioned cortical hubs of the central autonomic network in men, but with hypoperfusion of the hypothalamus in women. Linear regression analysis showed significant correlations of ASMI/cut-off with rCBF in the bilateral medial frontal cortex, as well as rCBF in the aforementioned key hubs. CONCLUSIONS: Hypoperfusion in key hubs of central autonomic network is implicated in the emergence of sarcopenia, probably through ASMI decline in vulnerable older adults. Geriatr Gerontol Int 2023; 23: 16-24.

[Smell and Taste Dysfunctions owing to COVID-19].

Olfactory and taste dysfunctions are characteristic symptoms of coronavirus disease 2019 (COVID-19); however, their frequencies and pathogeneses keep changing because of rapid mutations of the viral strains. Angiotensin-converting enzyme 2, a receptor for the spike protein of SARS-CoV-2 in the olfactory epithelium, is involved in the development of olfactory dysfunction. In general, olfactory dysfunctions resolve in a few weeks. However, there are cases wherein the symptoms persist for several months or longer, and parosmia or phantosmia affects the patient's quality of life. It is also assumed that the damage owing to COVID-19 extends to olfactory nerve cells, resulting in sensorineural olfactory dysfunction similar to post-infectious olfactory dysfunction.

A clinical survey on patients with taste disorders in Japan: A comparative study.

OBJECTIVE: To investigate changes in the clinical state of taste disorders between 1990, 2003, and 2019 using the same methodology as that in previous studies. MATERIALS AND METHODS: In June 2019, we mailed a questionnaire to 1100 otolaryngologists belonging to the Japan Society of Stomato-pharyngology and investigated three question categories: "Institution", "Number of patients for 3 months", and "Treatment". In addition, we analyzed some results by the class of institution. RESULTS: The rate of patients who complained of taste disorders in the 2019 survey (220/100,000 persons/year) was twice that of the 1990 survey (110/100,000 persons/year), and slightly higher than that of the 2003 survey (192/100,000 persons/year). The rate of female patients was higher than that of male patients in all age groups. The number of patients was correlated with age up to 70 years of age in both genders. The rates of performing taste tests to assess taste function in the 2019 survey were significantly decreased compared with a 2003 survey (electrogustometry: p<0.001, filter paper disk method: p<0.05 in university). The rate of examination of the serum zinc in the 2019 survey was increased compared with the 1990 survey (p<0.001). Zinc oral therapy was used for the treatment of taste disorders in 239/299 (79.9%) patients/institutes for 3 months. In addition, 213 institutions (69.6%) answered that zinc oral therapy was efficacious for taste disorders. CONCLUSION: The patients who complained of taste disorder have increased. The zinc administration is an appropriate clinical treatment for taste disorders in Japan. To enhance treatment for taste disorders, simpler methods for assessing taste function need to be developed, and the pathological mechanisms of taste disorders other than zinc deficiency need to be clarified.

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.

Olfactory-cognitive index distinguishes involvement of frontal lobe shrinkage, as in sarcopenia from shrinkage of medial temporal areas, and global brain, as in Kihon Checklist frailty/dependence, in older adults with progression of normal cognition to Alzheimer's disease.

AIM: Olfactory impairment as a prodromal symptom, as well as sarcopenia, frailty and dependence as geriatric syndromes, is often associated with cognitive decline in older adults with progression of Alzheimer's disease. The present study aimed to evaluate the associations of olfactory and cognitive decline with these geriatric syndromes, and with structural changes of the brain in older adults. METHODS: The participants were 135 older adults (47 men and 88 women, mean age 79.5 years), consisting of 64 with normal cognition, 23 with mild cognitive impairment and 48 with Alzheimer's disease. Olfactory function was evaluated by the Open Essence odor identification test. Shrinkage of the regional brain was determined by magnetic resonance imaging. RESULTS: Logistic regression analysis with Open Essence, Mini-Mental State Examination, age and sex as covariates showed higher olfactory-cognitive index (|coefficient for Open Essence (a) / coefficient for Mini-Mental State Examination (b)|) in participants with sarcopenia (Asia Working Group for Sarcopenia), and lower values of (|a/b|) in participants with Barthel Index dependence, Kihon Checklist frailty, Lawton Index dependence and support/care-need certification as objective variables. Logistic regression analysis adjusted by age and sex also showed significant shrinkage of the frontal lobe in participants with AWGS sarcopenia, especially in women, and shrinkage of the medial temporal areas and global brain in participants with Kihon Checklist frailty/dependence. CONCLUSIONS: Olfactory-cognitive index (|a/b|) might be a useful tool to distinguish involvement of frontal lobe shrinkage, as in sarcopenia from shrinkage of the medial temporal areas, and global brain, as in frailty/dependence, in older adults with progression of normal cognition to Alzheimer's disease. Geriatr Gerontol Int 2021; ••: ••-••.

Efficacy and Safety of Polaprezinc (Zinc Compound) on Zinc Deficiency: A Systematic Review and Dose-Response Meta-Analysis of Randomized Clinical Trials Using Individual Patient Data.

Zinc intake is recommended for zinc deficiency. In clinical practice, polaprezinc has been used as a zinc replacement therapy for zinc deficiency. However, the efficacy of polaprezinc has not been established. To confirm the efficacy on zinc deficiency of polaprezinc and provide additional information on an appropriate regimen, we conducted a systematic review using individual patient data (IPD). We searched PubMed, the Japanese database Ichushi, and the database owned by the marketing authorization holder of polaprezinc. Randomized placebo-controlled trials that reported the serum zinc concentration were eligible. The mean difference of the change from baseline in serum zinc concentration was estimated using a fixed-effects model. The linear dose-response relationship and the subgroup effects were also assessed. Out of 54 unique randomized clinical trials (RCTs), four studies met the eligibility criteria, and we could access IPD for all of them. All three doses of polaprezinc (75 mg, 150 mg, and 300 mg) and the placebo group were examined. The dose-combined overall polaprezinc increased the change from baseline by a mean of 9.08 µg/dL (95% confidence interval: 5.46, 12.70; heterogeneity: I2 = 0.61%) compared to the placebo. A significant dose-response relationship was confirmed (p < 0.001). Baseline serum zinc concentration was considered an effect modifier in polaprezinc 300 mg. All doses of polaprezinc were tolerable, but a dose-response relationship with adverse events (AEs) was observed in gastrointestinal disorders. The dose of 300 mg may be useful among patients with baseline serum zinc concentration of less than 70 µg/dL, and 150 mg for 70 µg/dL or more.

Thallium-201 Imaging in Intact Olfactory Sensory Neurons with Reduced Pre-Synaptic Inhibition In Vivo.

In this study, we determined whether the 201Tl (thallium-201)-based olfactory imaging is affected if olfactory sensory neurons received reduced pre-synaptic inhibition signals from dopaminergic interneurons in the olfactory bulb in vivo. The thallium-201 migration rate to the olfactory bulb and the number of action potentials of olfactory sensory neurons were assessed 3 h following left side nasal administration of rotenone, a mitochondrial respiratory chain complex I inhibitor that decreases the number of dopaminergic interneurons without damaging the olfactory sensory neurons in the olfactory bulb, in mice (6-7 animals per group). The migration rate of thallium-201 to the olfactory bulb was significantly increased following intranasal administration of thallium-201 and rotenone (10 µg rotenone, p = 0.0012; 20 µg rotenone, p = 0.0012), compared with that in control mice. The number of action potentials was significantly reduced in the olfactory sensory neurons in the rotenone treated side of 20 µg rotenone-treated mice, compared with that in control mice (p = 0.0029). The migration rate of thallium-201 to the olfactory bulb assessed with SPECT-CT was significantly increased in rats 24 h after the left intranasal administration of thallium-201 and 100 µg rotenone, compared with that in control rats (p = 0.008, 5 rats per group). Our results suggest that thallium-201 migration to the olfactory bulb is increased in intact olfactory sensory neurons with reduced pre-synaptic inhibition from dopaminergic interneurons in olfactory bulb glomeruli.