Orexin cell transplant reduces behavioral arrest severity in narcoleptic mice.

Narcolepsy is a sleep disorder that has been associated with the loss of orexinergic neurons from the lateral hypothalamic area. This loss leads to dysregulated sleep and cataplexy attacks. Therapeutic options are currently limited to symptom management with pharmacotherapy and nonpharmacological approaches. Nonetheless, cell replacement therapy could offer relief, and research in the field has yielded positive results for other neurodegenerative disorders, such as Parkinson's disease. Thus, we propose that orexin cell rich grafts could help improve narcoleptic symptoms in the orexin/ataxin-3 mouse model of narcolepsy. For this purpose, we isolated EGFP+ cells from either orexin/EGFP or CAG-EGFP mice with the use of a flow cytometer and grafted them into the pedunculopontine and laterodorsal tegmentum nuclei (PPT/LDDT) of orexin/ataxin-3 mice. Our results show that even small orexinergic grafts can reduce the severity of behavioral arrests, with a median reduction of 30.31% in episode duration, 51.35% for number of events and 69.73% in time spent in the behavioral arrest state and help with sleep fragmentation measured in number of bouts per behavioral state. Surprisingly, control grafts made from cerebellar tissue also reduced behavioral arrest severity, but to a lesser degree. Although still at a very early stage, these results show that there is potential in cell grafts for improving aspects of the narcoleptic phenotype and further research could help elucidate realistic expectations of an orexin cell replacement therapy for narcolepsy.

Chronic exercise modulates the cellular immunity and its cannabinoid receptors expression.

The impact of performing exercise on the immune system presents contrasting effects on health when performed at different intensities. In addition, the consequences of performing chronic exercise have not been sufficiently studied in contrast to the effects of acute bouts of exercise. The porpoise of this work was to determine the effect that a popular exercise regimen (chronic/moderate/aerobic exercise) has on the proportion of different immune cell subsets, their function and if it affects the cannabinoid system with potentially functional implications on the immune system. A marked increase in several immune cell subsets and their expression of cannabinoid receptors was expected, as well as an enhanced proliferative and cytotoxic activity by total splenocytes in exercised animals. For this study male Wistar rats performed treadmill running 5 times a week for a period of 10 weeks, at moderate intensity. Our results showed a significant decrease in lymphocyte subpopulations (CD4+, Tγδ, and CD45 RA+ cells) and an increase in the cannabinoid receptors expression in those same cell. Although functional assays did not reveal any variation in total immunoglobulin production or NK cells cytotoxic activity, proliferative capability of total splenocytes increased in trained rats. Our results further support the notion that exercise affects the immunological system and extends the description of underlying mechanisms mediating such effects. Altogether, our results contribute to the understanding of the benefits of exercise on the practitioner´s general health.

Cannabidiol Partially Blocks the Excessive Sleepiness in Hypocretindeficient Rats: Preliminary Data.

BACKGROUND: Excessive daytime sleepiness and cataplexy are among the symptoms of narcolepsy, a sleep disorder caused by the loss of hypocretin/orexin (HCRT/OX) neurons placed into the Hypothalamus (LH). Several treatments for managing narcolepsy include diverse drugs to induce alertness, such as antidepressants, amphetamine, or modafinil, etc. Recent evidence has shown that cannabidiol (CBD), a non-psychotropic derived from Cannabis sativa, shows positive therapeutic effects in neurodegenerative disorders, including Parkinson´s disease. Furthermore, CBD provokes alertness and enhances wake-related neurochemicals in laboratory animals. Thus, it is plausible to hypothesize that excessive somnolence observed in narcolepsy might be blocked by CBD. OBJECTIVE: Here, we determined whether the systemic injection of CBD (5mg/kg, i.p.) would block the excessive sleepiness in a narcoleptic model. METHODS: To test this idea, the neurotoxin hypocretin-2-saporin (HCRT2/SAP) was bilaterally injected into the LH of rats to eliminate HCRT leading to the establishment of narcoleptic-like behavior. Since excessive somnolence in HCRT2/SAP lesioned rats has been observed during the lights-off period, CBD was administered at the beginning of the dark phase. RESULTS: Hourly analysis of sleep data showed that CBD blocked the sleepiness during the lights-off period across 7h post-injection in lesioned rats. CONCLUSION: Taking together, these preliminary findings suggest that CBD might prevent sleepiness in narcolepsy.

The Substantia Nigra Is Permissive and Gains Inductive Signals When Lesioned for Dopaminergic Differentiation of Embryonic Stem Cells.

Transplantation of dopaminergic (DA) cells into the striatum can rescue from dopamine deficiency in a Parkinson's disease condition, but this is not a suitable procedure for regaining the full control of motor activity. The minimal condition toward recovering the nigrostriatal pathway is the proper innervation of transplanted DA neurons or their precursors from the substancia nigra pars compacta (SNpc) to their target areas. However, functional integration of transplanted cells would require first that the host SNpc is suitable for their survival and/or differentiation. We recently reported that the intact adult SNpc holds a strong neurogenic environment, but primed embryonic stem cells (ie, embryoid body cells, EBCs) could not derive into DA neurons. In this study, we transplanted into the intact or lesioned SNpc, EBCs derived from embryonic stem cells that were prompt to differentiate into DA neurons by the forced expression of Lmx1a in neural precursor cells (R1B5/NesE-Lmx1a). We observed that, 6 days posttransplantation (dpt), R1B5 or R1B5/NesE-Lmx1a EBCs gave rise to Nes+ and Dcx+ cells within the host SNpc, but a large number of Th+ cells derived only from EBCs exogenously expressing Lmx1a. In contrast, when transplantation was carried out into the 6-hydroxidopamine-lesioned SNpc, the emergence of Th+ cells from EBCs was independent of exogenous Lmx1a expression, although these cells were not found by 15 dpt. These results suggest that the adult SNpc is not only a permissive niche for initiation of DA differentiation of non-neuralized cells but also releases factors upon damage that promote the acquisition of DA characteristics by transplanted EBCs.

Genetic Knockdown of mGluR5 in Striatal D1R-Containing Neurons Attenuates L-DOPA-Induced Dyskinesia in Aphakia Mice.

L-DOPA is the main pharmacological therapy for Parkinson's disease. However, long-term exposure to L-DOPA induces involuntary movements termed dyskinesia. Clinical trials show that dyskinesia is attenuated by metabotropic glutamate receptor type 5 (mGluR5) antagonists. Further, the onset of dyskinesia is delayed by nicotine and mGluR5 expression is lower in smokers than in non-smokers. However, the mechanisms by which mGluR5 modulates dyskinesia and how mGluR5 and nicotine interact have not been established. To address these issues, we studied the role of mGluR5 in D1R-containing neurons in dyskinesia and examined whether nicotine reduces dyskinesia via mGluR5. In the aphakia mouse model of Parkinson's disease, we selectively knocked down mGluR5 in D1R-containing neurons (aphakia-mGluR5KD-D1). We found that genetic downregulation of mGluR5 decreased dyskinesia in aphakia mice. Although chronic nicotine increased the therapeutic effect of L-DOPA in both aphakia and aphakia-mGluR5KD-D1 mice, it caused a robust reduction in dyskinesia only in aphakia, and not in aphakia-mGluR5KD-D1 mice. Downregulating mGluR5 or nicotine treatment after L-DOPA decreased ERK and histone 3 activation, and FosB expression. Combining nicotine and mGluR5 knockdown did not have an added antidyskinetic effect, indicating that the effect of nicotine might be mediated by downregulation of mGluR5 expression. Treatment of aphakia-mGluR5KD-D1 mice with a negative allosteric modulator did not further modify dyskinesia, suggesting that mGluR5 in non-D1R-containing neurons does not play a role in its development. In conclusion, this work suggests that mGluR5 antagonists reduce dyskinesia by mainly affecting D1R-containing neurons and that the effect of nicotine on dyskinetic signs in aphakia mice is likely via mGluR5.

The artificial sweetener Splenda intake promotes changes in expression of c-Fos and NeuN in hypothalamus and hippocampus of rats.

BACKGROUND: Obesity is the result of the interaction of multiple variables, including the excessive increase of sugar-sweetened beverages consumption. Diets aimed to treat obesity have suggested the use of artificial sweeteners. However, recent evidence has shown several health deficits after intake of artificial sweeteners, including effects in neuronal activity. Therefore, the influence of artificial sweeteners consumption such as Splenda, on the expression of c-Fos and neuronal nuclear protein (NeuN) in hypothalamus and hippocampus remains to be determined. OBJECTIVES: We investigated the effects on c-Fos or NeuN expression in hypothalamus and hippocampus of Splenda-treated rats. METHODS: Splenda was diluted in water (25, 75 or 250 mg/100 mL) and orally given to rats during 2 weeks ad libitum. Next, animals were sacrificed by decapitation and brains were collected for analysis of c-Fos or NeuN immunoreactivity. RESULTS: Consumption of Splenda provoked an inverted U-shaped dose-effect in c-Fos expression in ventromedial hypothalamic nucleus while similar findings were observed in dentate gyrus of hippocampus. In addition, NeuN immunoreactivity was enhanced in ventromedial hypothalamic nucleus at 25 or 75 mg/100 mL of Splenda intake whereas an opposite effect was observed at 250 mg/100 mL of artificial sweetener consumption. Lastly, NeuN positive neurons were increased in CA2/CA3 fields of hippocampus from Splenda-treated rats (25, 75 or 250 mg/100 mL). CONCLUSION: Consuming Splenda induced effects in neuronal biomarkers expression. To our knowledge, this study is the first description of the impact of intake Splenda on c-Fos and NeuN immunoreactivity in hypothalamus and hippocampus in rats.

Transcranial magnetic stimulation as an antioxidant.

In the last decades, different transcranial magnetic stimulation protocols have been developed as a therapeutic tool against neurodegenerative and psychiatric diseases, although the biochemical, molecular and cellular mechanisms underlying these effects are not well known. Recent data show that those magnetic stimulation protocols showing beneficial effects could trigger an anti-oxidant action that would favour, at least partially, their therapeutic effect. We have aimed to review the molecular effects related to oxidative damage induced by this therapeutic strategy, as well as from them addressing a broader definition of the anti-oxidant concept.

Intrastriatal Chromospheres' Transplant Reduces Nociception in Hemiparkinsonian Rats.

The present study evaluates the possible antinociceptive effect of chromosphere transplants in rats injected with 6-hydroxydopamine (6-OHDA), a model of Parkinson's disease. Male adult Wistar rats received 40µg/0.5µl of 6-OHDA or 0.5µl of vehicle into the left substantia nigra (SNc). Rats were evaluated for mechanical allodynia, cold allodynia, thermal hyperalgesia and formalin. Rats with altered nociceptive threshold were transplanted with chromospheres. After transplant, rats were evaluated every week. Our results confirm that 6-OHDA injection into rat's SNc reduces mechanical, thermal, and chemical thresholds. Interestingly, chromospheres' transplant reverted 6-OHDA-induced allodynia and hyperalgesia. The antinociceptive effect induced by chromospheres was dopamine D2- and opioid-receptor dependent since sulpiride or naltrexone reverted its effect.

Comparative of transcranial magnetic stimulation and other treatments in experimental autoimmune encephalomyelitis.

The effects of transcranial magnetic stimulation (TMS), natalizumab (nata), dimethyl fumarate (DMF) and dexamethasone (DEX) on clinical score and oxidative stress produced by a single dose of myelin oligodendrocyte glycoprotein (MOG) in tail of Dark Agouti rats was studied. TMS (60Hz and 0.7 mT), nata (5mg/kg), DMF (15mg/kg) and DEX (300µg/kg) was applied for 21 after the administration of MOG (150µg). We estimated clinical score, as well as lipid peroxides, carbonylated proteins and reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio content in brain, spinal cord and blood. MOG triggered significant increase in clinical score and in the levels of lipid peroxides and carbonylated proteins levels, but reduced GSH/GSSG ratio in brain, spinal cord and blood. Both TMS and clinical treatments, although TMS more significantly, decreased the changes caused by MOG administration. These results support the antioxidant and neuroprotective action of TMS, as well as an activity higher than other clinical treatments.

Historical perspective of cell transplantation in Parkinson's disease.

Cell grafting has been considered a therapeutic approach for Parkinson's disease (PD) since the 1980s. The classical motor symptoms of PD are caused by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to a decrement in dopamine release in the striatum. Consequently, the therapy of cell-transplantation for PD consists in grafting dopamine-producing cells directly into the brain to reestablish dopamine levels. Different cell sources have been shown to induce functional benefits on both animal models of PD and human patients. However, the observed motor improvements are highly variable between individual subjects, and the sources of this variability are not fully understood. The purpose of this review is to provide a general overview of the pioneering studies done in animal models of PD that established the basis for the first clinical trials in humans, and compare these with the latest findings to identify the most relevant aspects that remain unanswered to date. The main focus of the discussions presented here will be on the mechanisms associated with the survival and functionality of the transplants. These include the role of the dopamine released by the grafts and the capacity of the grafted cells to extend fibers and to integrate into the motor circuit. The complete understanding of these aspects will require extensive research on basic aspects of molecular and cellular physiology, together with neuronal network function, in order to uncover the real potential of cell grafting for treating PD.

Recovery of glomerular morphology in the olfactory bulb of young mice after disruption caused by continuous odorant exposure.

Olfactory glomeruli are the first synaptic site of the olfactory system and are formed by the convergence of axons of the same type of sensory neurons onto the olfactory bulbs of the brain. Although the anatomical organization of glomeruli is conserved across species, their particular role in olfactory processing remains uncertain. We studied the composition and maintenance of glomeruli by means of a genetic model, mI7-IRES-tauGFP knock-in young mice, where the cytoskeleton of sensory neurons expressing the mI7 olfactory receptor is tagged with green fluorescent protein. Animals were continuously exposed to heptaldehyde, a cognate ligand of the mI7 receptor, from postnatal days 5-10. We hypothesized that continuous odorant exposure will induce changes in glomerular morphology, and that this can be recovered if the normal odorant environment is reestablished within the early postnatal period. We assessed changes in the distribution of mI7 axons in glomerular morphology, as well as possible changes in the number of the mI7 olfactory sensory neurons. Following odorant exposure the well-defined convergence of mI7 fibers into a single glomerulus was disrupted, producing numerous neighboring glomeruli partially innervated by mI7 fibers. After the normal odor environment was reestablished the number of glomeruli partially innervated by mI7 fibers decreased significantly. Moreover, we found that multiple supernumerary mI7 glomeruli were formed. Our results confirm the significant role of sensory input in glomerular formation and maintenance. Additionally, we show that the developing olfactory system actively maintains glomerular morphology, suggesting the importance of this for olfactory processing.

Understanding sleep-wake mechanisms and drug discovery.

INTRODUCTION: Although not discernible at first glance, sleep is a highly active and regulated brain state. Although we spend practically one third of our lifetimes in this stage, its importance is often taken for granted. Sleep loss can lead to disease, error and economic loss. Our understanding of how sleep is achieved has greatly advanced in recent years, and with that, the management of sleep disorders has improved. There is still room for improvement and recently many new compounds have reached clinical trials with a few being approved for commercial use. Areas covered: In this review, the authors make the case of sleep disorders as a matter of public health. The mechanisms of sleep transition are discussed emphasizing the wake and sleep promoting interaction of different brain regions. Finally, advances in pharmacotherapy are examined in the context of chronic insomnia and narcolepsy. Expert opinion: The orexinergic system is an example of a breakthrough in sleep medicine that has catalyzed drug development. Nevertheless, sleep is a topic still with many unanswered questions. That being said, the melanin-concentrating hormone system is becoming increasingly relevant and we speculate it will be the next target of sleep medication.

Effects of transcranial magnetic stimulation on oxidative stress in experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) reproduces a multiple sclerosis (MS)-like experimental model. The main objective was to evaluate the effect of extremely low-frequency electromagnetic fields (EL-EMF) application, like a paradigm of transcranial magnetic stimulation (TMS) in the development of EAE. Rats were injected with a single dose of 150 µg of myelin oligodendrocyte glycoprotein (MOG, fragment 35-55) to produce experimental MS. To assess the effect of TMS application in EAE, the rats were treated with TMS (60 Hz and 0.7 mT) for 2 h in the morning, once a day, 5 days a week, during 3 weeks. TMS was applied to the head. The effect of TMS on EAE was evaluated as motor symptoms and, oxidative and cell damage. The data showed that MOG induced motor symptoms as tail paralysis and limb paresis/paralysis, oxidative stress and cell death similar to MS when compared with control animals. Importantly, TMS application attenuated motor symptoms, oxidative and cell damage, whereas it increased antioxidant system. Our findings suggest that: (i) MOG reproduces an experimental model of MS characterised by oxidative and cell damage; and (ii) TMS application decreases oxidative stress and cell death induced by MOG.

Lipopolysaccharide Binding Protein and Oxidative Stress in a Multiple Sclerosis Model.

Recent findings in experimental autoimmune encephalomyelitis (EAE) suggest that altering certain bacterial populations present in the gut may lead to a proinflammatory condition, that could result in the development of multiple sclerosis (MS). Also, Reactive Oxygen Species seem to be involved in the course of MS. In this study, it has been aimed to relate all these variables starting from an analysis of the lipopolysaccharide (LPS) and LPS-binding protein (LBP) with the determination of parameters related to oxidative stress in the blood, brain and spinal cord. For this purpose, samples obtained from EAE rats and relapsing-remitting (RRMS) MS patients were used. In addition, EAE rats were treated with Natalizumab, N-acetyl-cysteine and dimethyl fumarate. Natalizumab was also employed in RRMS. The results of this study revealed an improvement in the clinical symptoms of the EAE and MS with the treatments, as well as a reduction in the oxidative stress parameters and in LBP. Correlations between the clinical variables of the disease, i.e. oxidative damage and LBP, were established. Although the conclusions of this research are indeed relevant, further investigation would be necessary to establish the intrinsic mechanisms of the MS-oxidative stress-microbiota relationship.

Transcranial magnetic stimulation modifies astrocytosis, cell density and lipopolysaccharide levels in experimental autoimmune encephalomyelitis.

AIMS: Experimental autoimmune encephalomyelitis (EAE) is considered a valid experimental model for multiple sclerosis, a chronic neuroinflammatory condition of the central nervous system. Additionally, some evidence has shown that some microbial products such as the bacterial lipopolysaccharide could lead to the activation of reactive immune cells, triggering neuroinflammation. Several studies have found that transcranial magnetic stimulation (TMS) may exert a neuroprotective effect. Therefore, we aimed to assess the effect of TMS on the neuroinflammation occurring in EAE. MATERIALS AND METHODS: A total of 44 male Dark Agouti rats were used. EAE induction was performed administering subcutaneously at the dorsal base of the tail a single dose of myelin oligodendrocyte glycoprotein. Clinical evaluation of motor symptoms was performed. Brain and spinal cord were collected and analyzed for nitric oxide, bacterial lipopolysaccharide and lipopolysaccharide-binding protein. We also carried out a histologic exam, which included an astrocyte immunostaining and Nissl staining for the assessment of brain cell density and pyknotic nuclei. KEY FINDINGS: TMS effectively ameliorated motor impairment secondary to EAE. This form of magnetic field was capable of decreasing the proliferation of astrocytes as a response to the autoimmune attack, reducing the content of nitric oxide, bacterial lipopolysaccharide and lipopolysaccharide-binding protein in central nervous system. Moreover, in treated animals, brain cell density was improved and the number of pyknotic nuclei was decreased. SIGNIFICANCE: Transcranial magnetic stimulation modifies astrocytosis, cell density and lipopolysaccharide levels in EAE. These results suggest that TMS could be a promising treatment for neuroinflammatory conditions such as multiple sclerosis.

Analgesic effect of repetitive transcranial magnetic stimulation (rTMS) in patients with chronic low back pain.

The objective of the present study was to assess the benefits of 1-week repetitive transcranial magnetic stimulation (rTMS) in patients with chronic low back pain (LBP). The visual analogue scale (VAS), Short Form McGill pain questionnaire (SF-MPQ), and Short Form 36 Health Survey were used to evaluate the effect of this treatment. Eighty-two patients diagnosed with LBP were divided randomly into three groups: rTMS-treated group, sham group, and physical therapy-treated group. We observed a significant reduction in VAS and SF-MPQ scores in the rTMS-treated group, but not in the sham group. Moreover, patients who received rTMS had a lower mean pain score than patients treated with physical therapy. Our study suggests that rTMS produces safe, significant, and long-term relief in patients with LBP without evident side effects. This study shows for the first time that long-term repeated sessions of rTMS decrease pain perception of LBP. Bioelectromagnetics. 37:527-535, 2016. © 2016 Wiley Periodicals, Inc.

Intrastriatal Grafting of Chromospheres: Survival and Functional Effects in the 6-OHDA Rat Model of Parkinson's Disease.

Cell replacement therapy in Parkinson's disease (PD) aims at re-establishing dopamine neurotransmission in the striatum by grafting dopamine-releasing cells. Chromaffin cell (CC) grafts produce some transitory improvements of functional motor deficits in PD animal models, and have the advantage of allowing autologous transplantation. However, CC grafts have exhibited low survival, poor functional effects and dopamine release compared to other cell types. Recently, chromaffin progenitor-like cells were isolated from bovine and human adult adrenal medulla. Under low-attachment conditions, these cells aggregate and grow as spheres, named chromospheres. Here, we found that bovine-derived chromosphere-cell cultures exhibit a greater fraction of cells with a dopaminergic phenotype and higher dopamine release than CC. Chromospheres grafted in a rat model of PD survived in 57% of the total grafted animals. Behavioral tests showed that surviving chromosphere cells induce a reduction in motor alterations for at least 3 months after grafting. Finally, we found that compared with CC, chromosphere grafts survive more and produce more robust and consistent motor improvements. However, further experiments would be necessary to determine whether the functional benefits induced by chromosphere grafts can be improved, and also to elucidate the mechanisms underlying the functional effects of the grafts.

Mouse embryonic stem cell-derived cells reveal niches that support neuronal differentiation in the adult rat brain.

A neurogenic niche can be identified by the proliferation and differentiation of its naturally residing neural stem cells. However, it remains unclear whether "silent" neurogenic niches or regions suitable for neural differentiation, other than the areas of active neurogenesis, exist in the adult brain. Embryoid body (EB) cells derived from embryonic stem cells (ESCs) are endowed with a high potential to respond to specification and neuralization signals of the embryo. Hence, to identify microenvironments in the postnatal and adult rat brain with the capacity to support neuronal differentiation, we transplanted dissociated EB cells to conventional neurogenic and non-neurogenic regions. Our results show a neuronal differentiation pattern of EB cells that was dependent on the host region. Efficient neuronal differentiation of EB cells occurred within an adjacent region to the rostral migratory stream. EB cell differentiation was initially patchy and progressed toward an even distribution along the graft by 15-21 days post-transplantation, giving rise mostly to GABAergic neurons. EB cells in the striatum displayed a lower level of neuronal differentiation and derived into a significant number of astrocytes. Remarkably, when EB cells were transplanted to the striatum of adult rats after a local ischemic stroke, increased number of neuroblasts and neurons were observed. Unexpectedly, we determined that the adult substantia nigra pars compacta, considered a non-neurogenic area, harbors a robust neurogenic environment. Therefore, neurally uncommitted cells derived from ESCs can detect regions that support neuronal differentiation within the adult brain, a fundamental step for the development of stem cell-based replacement therapies.

Sleep deprivation induces differential morphological changes in the hippocampus and prefrontal cortex in young and old rats.

Sleep is a fundamental state necessary for maintenance of physical and neurological homeostasis throughout life. Several studies regarding the functions of sleep have been focused on effects of sleep deprivation on synaptic plasticity at a molecular and electrophysiological level, and only a few studies have studied sleep function from a structural perspective. Moreover, during normal aging, sleep architecture displays some changes that could affect normal development in the elderly. In this study, using a Golgi-Cox staining followed by Sholl analysis, we evaluate the effects of 24 h of total sleep deprivation on neuronal morphology of pyramidal neurons from Layer III of the prefrontal cortex (PFC) and the dorsal hippocampal CA1 region from male Wistar rats at two different ages (3 and 22 months). We found no differences in total dendritic length and branching length in both analyzed regions after sleep deprivation. Spine density was reduced in the CA1 of young-adults, and interestingly, sleep deprivation increased spine density in PFC of aged animals. Taken together, our results show that 24 h of total sleep deprivation have different effects on synaptic plasticity and could play a beneficial role in cognition during aging.

Reference values of olfactory function for Mexico City inhabitants.

BACKGROUND AND AIMS: Olfactory testing is useful in the differential diagnosis of age-related pathologies. To provide baseline reference values for clinical use in Mexico City we investigated the relation between olfactory capabilities and the principal population parameters of age, sex, and smoking habits in a large sample of healthy inhabitants. METHODS: We applied the internationally recognized and commercially available Sniffin' Sticks test battery to 916 men and women from across the adult life span. The Sniffin' Sticks test evaluates three key aspects of olfactory function: 1) ability to detect an odor, 2) to discriminate between odors, and 3) to identify odors. RESULTS: We found a significant decline in olfactory function from the 5th decade of age, and that detection threshold was the most sensitive measure of this. We did not find a significant difference between men and women or between smokers and non-smokers. In confirmation of our previous studies of the negative effect of air pollution on olfactory function, Mexico City inhabitants had poorer overall performance than corresponding subjects previously tested in the neighboring but less polluted Mexican state of Tlaxcala. CONCLUSIONS: Although we basically confirm findings on general demographic patterns of olfactory performance from other countries, we also demonstrate the need to take into account local cultural, environmental and demographic factors in the clinical evaluation of olfactory performance of Mexico City inhabitants. The Sniffin' Sticks test battery, with some adjustment of stimuli to correspond to Mexican culture, provides an easily administered means of assessing olfactory health.