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.

Correlation between cerebral blood flow and olfactory function in mild cognitive impairment and Alzheimer's disease.

OBJECTIVE: Olfactory dysfunction is common in patients with mild cognitive impairment (MCI) or Alzheimer's disease (AD). We sought to elucidate brain regions associated with olfactory dysfunction in patients with MCI and early AD by using 123I-IMP-SPECT to detect regional cerebral blood flow (CBF). METHODS: We included 218 patients diagnosed with AD or MCI, who underwent a comprehensive battery of neuropsychiatric and neuropsychological tests, Alzheimer's Disease Assessment Scale-Cognitive Part (ADAS-Cog), and forward- and backward-digit span. Olfactory function was assessed using T&T olfactometry of five odors; patients stated whether they experienced any smell (detection test) and identified the odor (identification test). The association between single-photon emission computerized tomography based regional CBF and olfactory function was examined by voxel-by-voxel multiple regression analysis, considering sex, age, and education as covariate parameters. RESULTS: Of the 218 patients, 78 had mildly impaired olfactory detection and 15 had olfactory detection loss; additionally, 213 had mild olfactory identification impairment. The odor detection score correlated significantly with the ADAS-Cog word recall score (r = 0.193, p = 0.004). The odor identification score correlated significantly with the ADAS memory (r = 0.408, p < 0.001) and ADAS orientation (r = 0.292, p < 0.001) scores. The odor identification score correlated negatively with CBF in the left temporal pole, entorhinal area, and bilateral frontal poles (p < 0.001). CONCLUSION: Olfactory identification dysfunction in patients with MCI and AD is attributable to reduced CBF of the left temporal pole, entorhinal area, and bilateral frontal pole.

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; ••: ••-••.

Correlation between regional brain volume and olfactory function in very mild amnestic patients.

BACKGROUND & AIMS: We aimed to determine neural correlates of olfactory detection and identification and analyze associations between cognitive function and olfactory identification or detection in very mild amnestic patients. METHODS: We recruited 70 patients with chief complaints of memory impairment diagnosed as amnestic mild cognitive impairment (MCI) or Alzheimer's disease (AD) with a clinical dementia rating of 0.5. Olfactory detection and identification were assessed using T&T olfactometry. A voxel-wise correlation analysis of gray matter volume and olfactometry scores was performed. We also analyzed correlations between neuropsychological results and olfactometry scores. RESULTS: A significant negative correlation was observed between detection scores and nucleus accumbens and left parahippocampal gyrus volumes and between identification scores and orbitofrontal, right frontal, and right anterior temporal cortex volumes (p < .001). No significant correlation existed between detection and cognitive assessment scores. Identification score was significantly correlated with the Alzheimer's Disease Assessment Scale-Cognitive Part word recall score (r = 0.305, p = .01). CONCLUSIONS: Olfactory detection and identification dysfunction were attributable to impairments in different regions in MCI and very early AD; the former was attributed to the olfactory circuit, while the latter to neocortices. The dysfunction of identification of olfactory information was associated with episodic memory in those patients.

Comprehensive Detection of Respiratory Bacterial and Viral Pathogens in the Middle Ear Fluid and Nasopharynx of Pediatric Patients With Acute Otitis Media.

BACKGROUND: Acute otitis media (AOM) is a common ear infection caused by respiratory viruses and bacteria of the nasopharynx. The present study aimed to detect various respiratory viruses and bacteria in middle ear fluid (MEF) and nasopharyngeal aspirates (NPA) using polymerase chain reaction (PCR). METHODS: We collected MEF and NPA samples from 122 pediatric patients with AOM. Real-time PCR detected 11 types of respiratory viruses (respiratory syncytial virus A/B, parainfluenza virus 1/2/3, human metapneumovirus, influenza virus A/B, adenovirus, human bocavirus and rhino virus) and 7 types of bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Streptococcus pyogenes, Legionella pneumophila and Moraxella catarrhalis). MEF specimens were also examined using bacterial culture. RESULTS: At least 1 respiratory viral or bacterial pathogen was detected in MEF of 120 cases (98%) by viral and bacterial PCR and of 93 cases (76%) by viral PCR and bacterial culture. Respiratory viruses were detected in NPA of 84 cases (69%) and MEF of 67 cases (55%). The most common virus detected in MEF was respiratory syncytial virus (21%), followed by parainfluenza virus (15%). All the viruses present in MEF were also detected in NPA specimens. Bacteria were detected by PCR in MEF of 109 cases (89%); H. influenzae was the most frequently detected (65%). CONCLUSIONS: In many cases, pediatric AOM was found to constitute a respiratory polymicrobial infection. Multiplex PCR was useful to detect multiple respiratory viruses and bacteria in AOM. To understand intractable AOM, further studies regarding the clinical features of each viral and bacterial coinfection are required.

Olfactory Stimulation with Japanese Soy Sauce Improves Upper Limb Performance.

BACKGROUND: We have observed changes in body reactions during cooking, which is one of the treatment modalities used in occupational therapy. The perception of food-related odors during cooking may have behavioral effects on human activities through the activation of appetitive motivation. OBJECTIVES: We investigated whether odor components contained in seasonings could facilitate the human motor system and the specificity of this effect. METHODS: The subjects were 72 healthy adults, randomly assigned to a water exposure group, a phenylethyl alcohol (PEA, pleasant rose-like odor) exposure group, and a Japanese soy sauce (Koikuchi Shoyu) exposure group (n = 24 each). The subjects' olfactory sense was stimulated by their sniffing of three different test tubes containing 5 ml of water, PEA, or Japanese soy sauce for 20 sec while they were seated. The modified Functional Reach Test (mFRT), which mimics a functional activity that is required in daily living and assesses a reliable measure of sitting balance, was performed prior to and immediately after the sniffing. RESULTS: Sniffing the soy sauce increased the subjects' mFRT scores. This facilitation effect was odorant-specific and was absent when the subjects were presented with water or PEA. CONCLUSIONS: Cooking interventions are aimed at improving tool-handling skills such as using knives and chopsticks. The results indicate that treatment interventions using odors of seasonings would be effective for improving subjects' physical functions.

α2-Adrenergic receptor activation promotes long-term potentiation at excitatory synapses in the mouse accessory olfactory bulb.

The formation of mate recognition memory in mice is associated with neural changes at the reciprocal dendrodendritic synapses between glutamatergic mitral cell (MC) projection neurons and GABAergic granule cell (GC) interneurons in the accessory olfactory bulb (AOB). Although noradrenaline (NA) plays a critical role in the formation of the memory, the mechanism by which it exerts this effect remains unclear. Here we used extracellular field potential and whole-cell patch-clamp recordings to assess the actions of bath-applied NA (10 µM) on the glutamatergic transmission and its plasticity at the MC-to-GC synapse in the AOB. Stimulation (400 stimuli) of MC axons at 10 Hz but not at 100 Hz effectively induced N-methyl-d-aspartate (NMDA) receptor-dependent long-term potentiation (LTP), which exhibited reversibility. NA paired with subthreshold 10-Hz stimulation (200 stimuli) facilitated the induction of NMDA receptor-dependent LTP via the activation of α2-adrenergic receptors (ARs). We next examined how NA, acting at α2-ARs, facilitates LTP induction. In terms of acute actions, NA suppressed GC excitatory postsynaptic current (EPSC) responses to single pulse stimulation of MC axons by reducing glutamate release from MCs via G-protein coupled inhibition of calcium channels. Consequently, NA reduced recurrent inhibition of MCs, resulting in the enhancement of evoked EPSCs and spike fidelity in GCs during the 10-Hz stimulation used to induce LTP. These results suggest that NA, acting at α2-ARs, facilitates the induction of NMDA receptor-dependent LTP at the MC-to-GC synapse by shifting its threshold through disinhibition of MCs.

Tunicamycin impairs olfactory learning and synaptic plasticity in the olfactory bulb.

Tunicamycin (TM) induces endoplasmic reticulum (ER) stress and inhibits N-glycosylation in cells. ER stress is associated with neuronal death in neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, and most patients complain of the impairment of olfactory recognition. Here we examined the effects of TM on aversive olfactory learning and the underlying synaptic plasticity in the main olfactory bulb (MOB). Behavioral experiments demonstrated that the intrabulbar infusion of TM disabled aversive olfactory learning without affecting short-term memory. Histological analyses revealed that TM infusion upregulated C/EBP homologous protein (CHOP), a marker of ER stress, in the mitral and granule cell layers of MOB. Electrophysiological data indicated that TM inhibited tetanus-induced long-term potentiation (LTP) at the dendrodendritic excitatory synapse from mitral to granule cells. A low dose of TM (250nM) abolished the late phase of LTP, and a high dose (1µM) inhibited the early and late phases of LTP. Further, high-dose, but not low-dose, TM reduced the paired-pulse facilitation ratio, suggesting that the inhibitory effects of TM on LTP are partially mediated through the presynaptic machinery. Thus, our results support the hypothesis that TM-induced ER stress impairs olfactory learning by inhibiting synaptic plasticity via presynaptic and postsynaptic mechanisms in MOB.

Activation of arginine vasopressin receptor 1a facilitates the induction of long-term potentiation in the accessory olfactory bulb of male mice.

Olfaction plays an important role in social recognition in most mammals. Central arginine vasopressin (AVP) plays a role in this olfaction-based recognition. The high level of expression of AVP receptors in the accessory olfactory bulb (AOB) at the first relay of the vomeronasal system highlights the importance of AVP signaling at this stage. We therefore analyzed the effects of AVP on the synaptic plasticity of glutamatergic transmission from mitral cells to granule cells in AOB slices from male mice. To monitor the strength of the glutamatergic transmission, we measured the maximal initial slope of the lateral olfactory tract-evoked field potential, which represents the granule cell response to mitral cell activation. AVP paired with 100-Hz stimulation that only produced short-term potentiation enhanced the induction of long-term potentiation (LTP) in a dose-dependent manner. AVP-paired LTP was blocked by the selective AVP receptor 1a (AVPR1a) antagonist, d(CH2)5[Tyr(Me)2]AVP (Manning compound), but not by the AVPR1b antagonist SSR149415, and it was mimicked by the selective AVPR1a agonist [Phe2, Ile3, Orn8]-vasopressin. We further examined the effect of AVP on the reciprocal transmission between mitral and granule cells by stimulating a mitral cell and recording the evoked inhibitory postsynaptic currents (IPSCs) from the same cell using conventional whole-cell patch-clamp techniques. AVP reduced the reciprocal IPSCs triggered by endogenous glutamate release from the excited mitral cell. These results suggest that AVP promotes the induction of LTP at the mitral-to-granule cell synapse via the activation of AVPR1a through an as-yet-to-be-determined mechanism in the AOB of male mice.

Regulation of synaptic currents by mGluR2 at reciprocal synapses in the mouse accessory olfactory bulb.

The throughput of information from the accessory olfactory bulb (AOB) to downstream structures is controlled by reciprocal dendrodendritic inhibition of mitral cells by granule cells. Given the high expression levels of mGluR2, a metabotropic glutamate receptor, in the AOB and the fact that the activation of mGluR2 permits the formation of a specific olfactory memory, we reasoned that mGluR2 might play an important role in regulating dendrodendritic inhibition. To test this hypothesis, we examined the effects of pharmacological and genetic manipulations of mGluR2 on synaptic responses measured from mitral or granule cells in slice preparations from 23- to 36-day-old Balb/c mice. To evoke dendrodendritic inhibition, a depolarizing voltage step from -70 to 0 mV or a threshold current stimulus adjusted to elicit action potential(s) was applied to a mitral cell using either a nystatin-perforated or conventional whole-cell configuration. We found that an agonist for group II metabotropic glutamate receptors (mGluR2/mGluR3), DCG-IV [(2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine], suppressed, whereas the mGluR2/mGluR3 antagonist LY341495 [(αS)-α-amino-α-[(1S,2S)-2-carboxycyclopropyl]-9H-xanthine-9-propanoic acid] enhanced dendrodendritic inhibition. Genetic ablation of mGluR2 markedly impaired the effects of DCG-IV and LY341495 on dendrodendritic inhibition. DCG-IV reduced both the frequency and the amplitude of spontaneous miniature excitatory postsynaptic currents recorded from granule cells. Additionally, DCG-IV inhibited high-voltage-activated calcium currents in both mitral and granule cells. These results suggest that mGluR2 reduces dendrodendritic inhibition by inhibiting synaptic transmission between mitral cells and granule cells in the AOB.

Evaluation of "Open Essence" odor-identification test card by application to healthy volunteers.

OBJECTIVE: In the United States and European countries, the University of Pennsylvania Smell Identification Test (UPSIT), the Quick Smell Identification Test (Q-SIT), a shorter version of the UPSIT, and "Sniffin' Sticks" are widely used for testing olfaction. The odor stick identification test for Japanese (OSIT-J) has been manufactured in Japan. This was followed by the development of "Open Essence," consisting of cards that make use of sealed odorants. This study examined the usefulness of Open Essence in young volunteers with normal olfaction. METHOD: The participants were 176 medical students in their clinical clerkships at the Department of Otolaryngology, Kochi Medical School Hospital. There were 111 males and 65 females, with a median age of 24 years (range 22-42 years). The olfactory function of all participants was confirmed as normal by screening with T&T olfactometry. Before beginning Open Essence, the subjects were asked to answer a questionnaire on their olfaction and habits. RESULTS: Females had significantly better smell identification than males. Of the 12 odorants, "perfume" and "cooking gas" were difficult to identify, because perfume involves different imagery and the compounds that give the smell of gas are readily volatilized. In contrast, all participants recognized "curry" and "menthol," probably because they are received as both somatosensory stimuli and smell. CONCLUSIONS: These results suggest that, with improvement, Open Essence might be used for testing olfaction in Japanese subjects.

Effects of olfactory stimulation with isovaleric acid on brain activation in informed and naïve conditions: a functional MRI study.

OBJECTIVE: To investigate the differences in regions of brain activation in response to olfactory stimulation by functional magnetic resonance imaging in conditions of prior warning of an odor and without. METHODS: Participants were 17 normal right-handed volunteers; 8 participants received prior warning of the odor (informed condition) and 9 participants were not pre-warned (naïve condition). The odorant used was isovaleric acid. RESULTS: In the informed condition with prior warning, activation was observed in the putamen extending to the insula, amygdala, and inferior frontal gyrus, and there was instant reification of the odor, while in the naïve condition without prior warning, activation was observed in the anterior cingulate cortex, entorhinal cortex, putamen and inferior frontal gyrus, and recognition of the odor was difficult. CONCLUSIONS: These results suggest that the condition prior to olfactory stimulation, i.e., with or without prior warning, can affect recognition and regions of brain activation in response to olfactory stimulation using isovaleric acid. Differences in recognition and regions of brain activation between both conditions could be associated with response latencies, or degree of attention, expectation and/or concentration.

Modulation of olfactory learning in young rats through intrabulbar GABA(B) receptors.

After training with an odour paired with foot shock on postnatal day 11, rat pups show an aversion to the odour in testing on postnatal day 12. The mechanisms underlying this aversive olfactory learning involve disinhibition of mitral/tufted cells in the olfactory bulb by the somatosensory stimulation-induced activation of centrifugal noradrenergic fibres originating in the locus coeruleus. The activity of mitral/tufted cells is regulated through gamma-aminobutyric acidA (GABA(A)) receptors in the external plexiform layer and GABA(B) receptors in the glomerular layer. We have previously presented that aversive olfactory learning in young rats is modulated through GABA(A) receptors in the olfactory bulb. In the present study we examined the consequence of manipulating GABA(B) receptors in the olfactory bulb during training. Baclofen, a GABA(B) receptor agonist when infused into the olfactory bulb during the pairing of an odour with foot shock, prevented aversive olfactory learning in a dose-dependent manner. Infusion of saclofen, a GABA(B) receptor antagonist, during training with a citral odour in the absence of foot shock produced aversive responses not only to the odour, but also to strange odours (benzaldehyde and vanillin) not previously presented. Such olfactory aversions were observed even if saclofen was infused without odour exposure. These results suggest that olfactory learning in young rats is modulated through GABA(B) receptors in the olfactory bulb.