Effects of methyl bromide on the rat olfactory system

The nature and extent of damage produced by methyl bromide (MeBr)exposure, and recovery of function after exposure, were studiedusing a multifacct approach which included behavioral, morphologicaland neurochemical endpoints. Thirty adult male Long–Evansrats were exposed to 200 p.p.m. MeBr for 4 h/day, 4 days a weekfor 2 weeks. Fifteen control rats were exposed to filtered aironly. On the first day following the onset exposure to MeBr,extensive damage to the olfactory epithelium as well as greatlyimpaired olfactory function were observed. However, even withcontinuous MeBr exposure, olfactory function was essentiallynormal after 4 days of exposure. Repair of the epithelium wasin progress by day 4 although morphology was atypical. The levelsof carnosine in both the olfactory epithelium and bulbs wereseverely depleted by day 4. Recovery, both in terms of structuralrepair and return of normal carnosine concentrations, laggedfar behind recovery of the ability to detect an odor stimulus.Even with repeated exposure, olfactory function recovered rapidly,even faster than anatomical repair. Measurement of overall carnosinelevels correlated well with the results obtained from representativeareas of tissues selected for histopathology. Morphometric analysisprovided quantitative detail on the nature of insult resultingfrom MeBr exposure. These data indicate that the olfactory systemis a most resilient system and that normal function is possibleeven after repeated insult by a toxic agent.     

Innate immune responses and neuroepithelial degeneration and regeneration in the mouse olfactory mucosa induced by intranasal administration of Poly(I:C)

The pathogenesis of postviral olfactory disorder (PVOD) has not been fully elucidated. We investigated morphological changes and innate immune responses in the mouse olfactory mucosa induced by intranasal administration of polyinosinic-polycytidylic acid [Poly(I:C)], a synthetic analog of viral double-stranded RNA. Mice received three administrations of saline with or without Poly(I:C), once every 24 h. The olfactory mucosa was harvested at various intervals after the first administration (8 h, 3, 9 and 24 days). In the Poly(I:C) group, the number of apoptotic cells in the olfactory neuroepithelium had increased at 8 h. At 9 days, the olfactory neuroepithelium had severely degenerated and behavioral tests demonstrated that the mice showed signs of olfactory deterioration. At 24 days, the structure of the neuroepithelium had regenerated almost completely. Regarding the innate immune responses, many neutrophils had infiltrated the olfactory neuroepithelium at 8 h and had exuded into the nasal cavity by 3 days. Macrophages had also infiltrated the olfactory neuroepithelium at 8 h although to a lesser extent, but they still remained in the neuroepithelium at 24 days. Poly(I:C)-induced neuroepithelial damage was significantly inhibited by a neutrophil elastase inhibitor and was suppressed in neutropenic model mice. These findings suggest that the secondary damage caused by the neutrophil-mediated innate immune response plays an important role in the pathogenesis of PVOD.     

Basal cells in the mouse olfactory epithelium after axotomy: immunohistochemical and electron-microscopic studies

Summary The olfactory epithelium of mice after axotomy was investigated to clarify the stem cells of olfactory cells by double immunostaining using antikeratin (MA903) and anti-bromodeoxyuridine (BrdU) antibodies and by conventional electron microscopy. When a single dose of BrdU was given to mice 9 days after axotomy, immunostaining for BrdU was found in the globose basal cells which were negative for MA903, but not in the basal cells proper which were positive for MA903. The BrdU-immunoreactive cells increased 3-to 6-fold over the number of these cells in the controls, indicating active cell proliferation. At other postoperative days (4 and 14 days), fewer BrdU-immunoreactive cells were found. Furthermore, three pulses of BrdU resulted in numerous BrdU-immunolabelings in the globose basal cells and a few in the basal cells proper. There was no detectable difference in the number of labeled basal cells proper in operated and unoperated mice. In the electron micrographs 9 days after axotomy, the basal cells proper, flat-shaped in unoperated mice, appeared cylindrical or pyramidal in shape and the globose basal cells often lay between the basal cells proper. In unoperated controls, the globose basal cells were located above the flat-shaped basal cells proper. The results suggest that the stem cells of the olfactory cells are globose basal cells and not basal cells proper, and that the shape of basal cells proper changes in relation to the active proliferation of stem cells.     

Antioxidant-chemoprevention diet ameliorates late effects of total-body irradiation and supplements radioprotection by MnSOD-plasmid liposome administration

Abstract Many acute and chronic effects of ionizing radiation are mediated by reactive oxygen species and reactive nitrogen species, which deplete antioxidant stores, leading to cellular apoptosis, stem cell depletion and accelerated aging. C57BL/6NHsd mice receiving intravenous MnSOD-PL prior to 9.5 Gy total-body irradiation (TBI) show increased survival from the acute hematopoietic syndrome, and males demonstrated improved long-term survival (Epperly et al., Radiat. Res. 170, 437-444, 2008). We evaluated the effect of an antioxidant-chemopreventive diet compared to a regular diet on long-term survival in female mice. Twenty-four hours before the LD(50/30) dose of 9.5 Gy TBI, subgroups of mice were injected intravenously with MnSOD-PL (100 μg plasmid DNA in 100 μl of liposomes). Mice on either diet treated with MnSOD-PL showed decreased death after irradiation compared to irradiated mice on the house diet alone (P = 0.031 for the house diet plus MnSOD-PL or 0.015 for antioxidant diet plus MnSOD-PL). The mice on the antioxidant-chemoprevention diet alone or with MnSOD-PL that survived 30 days after irradiation had a significant increase in survival compared to mice on the regular diet (P = 0.04 or 0.01, respectively). In addition, mice treated with MnSOD-PL only and surviving 30 days after radiation also had increased survival compared to those on the regular diet alone (P = 0.02). Survivors of acute ionizing radiation damage have ameliorated life shortening if they are fed an antioxidant-chemopreventive diet.     

Roles of the main olfactory and vomeronasal systems in the detection of androstenone in inbred strains of mice

We investigated the role of the main olfactory and accessory olfactory systems (MOS and AOS respectively) in the detection of androstenone. We used the following experimental approaches: behavioral, surgical removal of the vomeronasal organ (VNX) followed by histochemical verification and Fos immunohistochemistry. Using a Y-maze paradigm we estimated sensitivity of NZB/B1NJ and CBA/J mice to androstenone. CBA mice were 2,000-fold more sensitive to androstenone than NZB mice. VNX caused a 4- to 16-fold decre...     

Expression of adiponectin receptor 1 in olfactory mucosa of mice

AdipoR1 and AdipoR2 are receptors for the adipocyte-derived hormone adiponectin, which is an important regulator of glucose and lipid metabolism, and which has also been implicated in the control of food intake and energy homeostasis. In the present study, we have demonstrated that AdipoR1 is expressed in mature sensory neurons of the olfactory mucosa of mice, in a pattern reminiscent of the olfactory marker protein. AdipoR1 expression levels in the olfactory mucosa have been observed to increase gradually during late embryogenesis until adulthood. No local expression of adiponectin has been detected in nasal tissues, indicating that serum adiponectin is the ligand for AdipoR1 in olfactory sensory neurons. As the serum adiponectin concentration is regulated depending on adipose tissue mass, with a reduction of adiponectin levels being seen in obesity, AdipoR1 function in the olfactory epithelium seems to be directly linked to the nutritional status of the body, suggesting a potential modulatory role for AdipoR1 in the adjustment of the olfactory system to energy balance requirements. This work was supported by the Forschungsfonds ZEM Tübingen/Hohenheim. Nicole Hass is recipient of a Peter und Traudl Engelhorn Stiftung scholarship.     

Effects of anticancer drug docetaxel on the structure and function of the rabbit olfactory mucosa

Docetaxel (DCT) is an anticancer drug which acts by disrupting microtubule dynamics in the highly mitotic cancer cells. Thus, this drug has a potential to affect function and organization of tissues exhibiting high cellular turnover. We investigated, in the rabbit, the effects of a single human equivalent dose (6.26 mg/kg, i.v.) of DCT on the olfactory mucosa (OM) through light and electron microscopy, morphometry, Ki-67 immunostaining, TUNEL assay and the buried food test for olfactory sensitivity. On post-exposure days (PED) 5 and 10, there was disarrangement of the normal cell layering in the olfactory epithelium (OE), apoptotic death of cells of the OE, Bowman's glands and axon bundles, and the presence (including on PED 3) of blood vessels in the bundle cores. A decrease in bundle diameters, olfactory cell densities and cilia numbers, which was most significant on PED 10 (49.3%, 63.4% and 50%, respectively), was also evident. Surprisingly by PED 15, the OM regained normal morphology. Furthermore, olfactory sensitivity decreased progressively until PED 10 when olfaction was markedly impaired, and with recovery from the impairment by PED 15. These observations show that DCT transiently alters the structure and function of the OM suggesting a high regenerative potential for this tissue.     

Renewing olfactory receptor neurons in goldfish do not require contact with the olfactory bulb to develop normal chemical responsiveness

This study investigated whether contact with the olfactory bulb was necessary for developing and renewing olfactory receptor neurons (ORNs) to attain normal odorant responsiveness, and whether the anatomical and functional recoveries of the olfactory epithelium were similar in both bulbectomized (BE) and bilaterally axotomized (AX) preparations. In vivo electrophysiological recordings were obtained in response to amino acids, a bile acid [taurolithocholic acid sulfate(TLCS)] and a pheromonal odorant [17α, 20β,-dihydroxy-4-pregnen-3-one (17,20P)] from sexually immature goldfish. Both transmission and scanning electron microscopy indicated that the olfactory epithelium degenerated in BE and AX goldfish. Within 1–2 weeks subsequent to the respective surgeries, responses to high concentrations (>0.1 mmol · l⁻¹) of the more stimulatory amino acids remained, whereas responses were no longer obtainable to TLCS and 17,20P. At 4 weeks, responses to amino acid stimuli recovered to control levels, while responses to TLCS and 17,20P were minimal. By 7 weeks post bilateral axotomy, the olfactory epithelium recovered to a condition similar to control sensory epithelium; however, the rate of degeneration and proliferation of receptor neurons in BE preparations appeared to remain in balance, thus blocking further recovery of the olfactory epithelium. At 7 weeks post surgery, odorant responses of AX and BE goldfish to TLCS and 17,20P were still recovering. Accepted: 14 June 1997     

Food restriction-like effects of dehydroepiandrosterone: decreased lymphocyte numbers and functions with increased apoptosis.

Both dietary dehydroepiandrosterone (DHEA) and food restriction can prevent or modulate the initiation or progression of a number of diseases in rodents and prolong life span. We sought to determine if these interventions have common mechanisms of action in regulating lymphocyte functions and cell numbers. We observed that male C57BL/6 mice receiving DHEA in the diet (0.45%, w/w) ate approximately 50% as much food as mice on the DHEA-free diet, and this was reflected in decreased body weights throughout a 10-week period. Mice either fed the DHEA-containing diet or pair-fed to the DHEA-treated mice had decreased spleen and thymus weights and lymphocyte cell numbers compared to mice having free access to the control diet. Mice were fed these diets for 2 weeks before and 2 weeks after exposure to sublethal irradiation (500 cGy). In mice fed DHEA or pair-fed, there was a decrease in spleen cell numbers, and B cells were the most severely affected. The frequency of apoptosis in peripheral blood cells increased from <5% in nonirradiated controls to >50% within 4 days after starting DHEA or pair-feeding. Shortly after irradiation, >87% of blood lymphocytes were hypodiploid (apoptotic) in all groups. By 9 days only 27% of lymphocytes in mice on the control diet were hypodiploid compared to 62% in DHEA and 74% in pair-fed mice. In addition, both DHEA and pair-fed mice had significant reductions in T-cell function (contact hypersensitivity to dinitrofluorobenzene), B cell function (antibody response to trinitrophenolated-lipopolysaccharide), and NK cell function (lung clearance of radiolabeled YAC-1 tumor cells) 2 weeks after irradiation. In a complementary study, peripheral blood lymphocytes from na?ve mice were treated overnight with various concentrations of either DHEA or hydrocortisone 21-acetate. Only glucocorticoid-treated cells underwent apoptosis. Thus, DHEA induces apoptosis in vivo but not in vitro. We conclude that dietary DHEA induces apoptosis and decreased lymphocyte production and function in C57BL/6 mice largely by reducing food intake.     

Behavioral differentiation during collective building in wild mice Mus spicilegus

Although well documented in social insects, the possibility of behavioral differentiation during collective building has been poorly studied in mammals. In this context, the mound-building mouse Mus spicilegus is an interesting model. Under natural conditions, juveniles from different litters gather vegetal material and build a sophisticated structure, the mound, under which the mice will spend winter. The first steps of this complex building process may be elicited under laboratory conditions by offering cotton balls as building material. Spatio-temporal distribution of both animals and cotton balls was automatically recorded by RFID (Radio-Frequency Identification Device) technique. Our results revealed a behavioral differentiation during a collective building task. In a group of six individuals, only two mice (called carriers) transported 80% of the building material whereas the contribution of the remaining mice was weak or even non-existent. The proportion of carriers was constant in all of the six groups studied. This behavioral differentiation was implemented immediately after the building material was made available and remained stable during the 4 days of experiment. The high contribution level of carriers did not result from resource monopolization, nor did it depend on the gender or parental origin of the mice.     

Conjugated Linoleic Acid Does Not Improve Insulin Tolerance in Mice*

Objective: To determine if the addition or removal of dietary conjugated linoleic acid (CLA) would alter insulin tolerances in mice from two genetic lines. Research Methods and Procedures: High metabolic rate (MH) and low metabolic rate (ML) mice were assigned to consume 1) a control diet ad libitum, 2) a control diet at a restricted intake, or 3) a diet containing 1% CLA ad libitum. After 9 weeks, an insulin tolerance test was conducted, and a portion of the mice were killed. All remaining mice consumed the control diet ad libitum. Insulin tolerance tests were conducted 11 and 32 days after the diet change, and mice were killed 3 days after each test. Body fatness, fat pad weights, and serum insulin concentrations of mice were determined at each time‐point. Two follow‐up experiments were also conducted. Results: Restricted mice had insulin sensitivities not different than control mice. CLA‐fed MH mice in experiment 1 were resistant (p < 0.001) to insulin on each day measured. CLA‐fed ML mice were slightly resistant (p = 0.08) to exogenous insulin on day 0 of recovery and not different from control mice on day 11 or 32. Glucose response to insulin in MH mice fed CLA in experiments 2 or 3 did not differ from control mice. Discussion: Mice fed CLA did not have improved insulin tolerances compared with control mice. In some cases, dietary CLA may cause insulin resistance. MH mice seem more sensitive to CLA than ML mice.     

Effect of folic acid deficiency upon lymphocyte subsets from lymphoid organs in mice.

1. Three groups of weanling C57BL/6 female mice were fed one of two folate-deficient diets (0 and 0.1 mg folic acid/kg diet) or a normal folate-containing diet (2 mg folic acid/kg diet) for 8 weeks. A control pair-fed group was introduced with the most severe folate-deficient diet. Seven mice were fed the 0 mg folic acid/kg diet for 8 weeks, then rehabilitated (R) on the 2 mg folic acid/kg diet for 10 days. 2. Mice fed 0 mg folic acid/kg diet were severely folate-deficient (SFD), whereas mice fed 0.1 mg folic acid/kg diet were moderately folate-deficient (MFD), as shown by their folate status parameters. 3. Thymus weight, thymocyte content and positive immature CD4+8+ cells were decreased in SFD mice compared to controls. These values were normalized after 10 days of rehabilitation. 4. Mesenteric lymph node cells were apparently not affected by folate deficiency. 5. The proportion of Thy-1+ splenocytes was mildly lower in SFD mice than in controls. In R mice, mean spleen weight and spleen cellularity were increased compared to the other groups, but the proportions of Thy-1+, CD4+8- and CD4-8+ cells were markedly lower than control values.     

Diet and abdominal autofluorescence detected by in vivo fluorescence imaging of living mice

We investigated the effect of diet on abdominal autofluorescence detected by in vivo fluorescence imaging (FLI) of living mice. Groups of mice were fed a regular, alfalfa-free, or purified diet, and whole-body FLI was performed without the administration of fluorescent probes. In addition, quantum dots were injected intravenously into mice fed one of the three diets, and FLI was performed 3 and 24 hours later. Intense autofluorescence originating from the animals' intestinal contents was observed in mice fed the regular diet. Intestinal autofluorescence decreased substantially after feeding with the alfalfa-free diet and further after feeding with the purified diet. The decline was rapid and took only 1 to 2 days; however, it may have been affected by an intake of feces. The reticuloendothelial system was clearly delineated using a low dose of quantum dots in mice fed the purified diet. On the other hand, intestinal autofluorescence was visible 24 hours postinjection in mice given the alfalfa-free diet and definitely impaired the image quality in mice fed the regular diet. The use of a low-fluorescence diet, especially a purified diet, rapidly reduces intestinal autofluorescence and is expected to enhance the potential of in vivo FLI.     

The mouse bioassay for the detection of estrogenic activity in rodent diets: I. A standardized method for conducting the mouse bioassay

A standardized procedure was developed for conducting the mouse bioassay for detecting estrogenic activity in rodent diets. Studies were conducted with CD-1 mice to determine the appropriate weaning age and length of bioassay period. Uterine growth curves were generated from mice weaned at 15 days of age and fed a negative control diet until 28 days of age. These mice showed slow regular increases in uterine weights from 15 22 days of age followed by rapid uterine growth in some mice from 24 to 28 days of age. Estrogenic bioassays using female mice weaned at 15 days of age and fed the positive control diets containing 4 or 6 ppb diethylstilbestrol (DES) demonstrated significant (P less than 0.05) increases in uterine weight and in uterus to body weight (U:BW) ratios over those of mice fed the negative control diet without DES for 5, 7 or 9 days after weaning. In contrast, mice weaned at 17 days of age showed significant (P less than 0.05) increases in uterine weight and in U:BW ratios only at 5 days after weaning. Six ppb DES was required in the positive control diet to produce a 1.5 fold increase in the U:BW ratio over those of mice fed the negative control diet. It was concluded that mice should be weaned at 15 days of age and that the bioassay period should be terminated at 7 days, when the mice are 22 days old, for best reproducible results. The criteria for a valid bioassay should include the demonstration of a significant statistical increase in the U:BW ratios of mice fed the DES positive diet over those of mice fed the negative control diet.     

In goldfish the discriminative ability for odours persists after reduction of the olfactory epithelium, and rapidly returns after olfactory nerve axotomy and crossing bulbs

Goldfish are ideal vertebrates for the study of regeneration within the peripheral and the central olfactory system. The present behavioural investigations studied the effects of bilateral lesions on the animals' ability to qualitatively discriminate two amino acids (10(-6) M) and their performance in two more difficult tasks: (i) rewarded amino acid applied in a lower concentration, and (ii) rewarded stimulus contaminated. A 50 and 85% reduction of the olfactory epithelium resulted in no recordable behavioural deficit. After axotomy of olfactory nerves and lateral olfactory tractotomy, fishes were anosmic for seven to ten days. Following replacement of sensory cells in the epithelium, and after regeneration of olfactory tract fibres a full functional recovery i.e. a highly specific regeneration, was recorded. After three surgical modifications of the olfactory bulbs' position, (i) crossing olfactory tracts and bulbs, (ii) crossing tracts and turning bulbs, and (iii) turning bulbs upside down, a full functional recovery was recorded for amino-acid discrimination in a similar concentration. A permanent, and similar slight deficit was, however, found during application of different concentrations, and of contaminated stimuli when medial lateral halves of the bulb were in 'incorrect' position (i) and (ii), or olfactory bulbs were positioned in the vicinity of the contralateral epithelium (i) and (ii).     

Functional and morphological regeneration of olfactory tracts and subtracts in goldfish

Goldfish are ideal vertebrates for the study of regeneration within the central nervous system. The present behavioural and neuroanatomical investigations after bilateral transection of the entire olfactory tracts of either lateral or medial subtracts have been designed (1) to examine the relationship between morphological changes and changes in the perception of spontaneously preferred chemosensory stimuli, (2) to investigate the animals' ability to qualitatively discriminate amino acids in olfactory concentrations (below taste threshold, 10^-6–10^-8 M), one of which had been rewarded preoperatively (specific regeneration), and (3) to examine the discriminative ability for amino acids at concentrations above taste threshold (> 10^-5 M) in intact sham-operated, and in operated specimens at various time intervals before functional regeneration. Within 10–14 days after bilateral transection of the lateral olfactory tracts, specific regeneration was observed. After bilateral transection of the medial olfactory tracts, no immediate behavioural change was recorded for 1 week. Thereafter, goldfish behaviour became unstable and dropped to the chance level for 3–4 weeks. Subsequent to this time the goldfish returned to the preoperative level. Following bilateral crushing of the olfactory tracts and after total tractotomy, a specific regeneration was observed after 4 weeks and 6–8 weeks, respectively, post op. HRP studies showed that after bilateral lesioning a qualitative reinnervation of the respective nuclei within the forebrain by the medial and lateral olfactory subtracts was evident.Abbreviations FB funnel biting - FO funnel orientation - HRP horseradish peroxidase - LOT lateral olfactory tract - MOT medial olfactory tract     

Axon Guidance Events in the Wiring of the Mammalian Olfactory System

The detection of odorant signals from the environment and the generation of appropriate behavioral outputs in response to these signals rely on the olfactory system. Olfactory sensory neurons (OSNs) of the olfactory epithelium are located in the nasal cavity and project axons that synapse onto dendrites of second-order neurons in the olfactory bulb (OB) that in turn relay the information gathered to higher order regions of the brain. The connections formed are remarkably accurate such that axons of OSNs expressing the same olfactory receptor innervate specific glomeruli within the complex three-dimensional structure that represents the OB. The molecular determinants that control this complex process are beginning to be identified. In this review, we discuss the role of various families of axon guidance cues and of recently characterized families of adhesion molecules in the formation of stereotypic connections in the olfactory system of mice. Cho and Prince contributed equally.     

Ciliated olfactory receptor neurons in goldfish (Carassius auratus) partially survive nerve axotomy,rapidly regenerate and respond to amino acids

Electro-olfactogram (EOG) recordings in response to amino acid stimulation were made from both control and experimental olfactory mucosae following unilateral axotomy. The recorded EOG amplitudes, amino acid stimulus relative effectiveness and dose-response relations for control and experimental mucosae were comparable in all pre- and postoperative recordings. Semi-thin investigations of olfactory mucosae showed degeneration of olfactory receptors but indicated that intact receptors were also present. SEM of olfactory mucosae revealed that ciliated receptor cells were present in both axotomized and control sides on postoperative days, whereas microvillous receptors completely degenerated and did not regenerate until 7 weeks post axotomy. The present findings along with previous behavioral observations suggest at least three possible sources of the EOGs recorded from the experimental olfactory mucosae following olfactory nerve transection: (1) young olfactory receptor neurons whose axons had not yet reached the region of the transected olfactory nerve; (2) newly-emerged olfactory receptor neurons; and (3) olfactory receptor neurons that had not degenerated.Abbreviations EOG electro-olfactogram - SEM scanning electron microscopy (micrograph)     

High-fat diet-induced lipidome perturbations in the cortex,hippocampus, hypothalamus,and olfactory bulb of mice

Given their important role in neuronal function, there has been an increasing focus on altered lipid levels in brain disorders. The effect of a high-fat (HF) diet on the lipid profiles of the cortex, hippocampus, hypothalamus, and olfactory bulb of the mouse brain was investigated using nanoflow ultrahigh pressure liquid chromatography-electrospray ionization-tandem mass spectrometry in the current study. For 8?weeks, two groups of 5-week-old mice were fed either an HF or normal diet (6 mice from each group analyzed as the F and N groups, respectively). The remaining mice in both groups then received a 4-week normal diet. Each group was then subdivided into two groups for another 4-week HF or normal diet. Quantitative analysis of 270 of the 359 lipids identified from brain tissue revealed that an HF diet significantly affected the brain lipidome in all brain regions that were analyzed. The HF diet significantly increased diacylglycerols, which play a role in insulin resistance in all regions that were analyzed. Although the HF diet increased most lipid species, the majority of phosphatidylserine species were decreased, while lysophosphatidylserine species, with the same acyl chain, were substantially increased. This result can be attributed to increased oxidative stress due to the HF diet. Further, weight-cycling (yo-yo effect) was found more critical for the perturbation of brain lipid profiles than weight gain without a preliminary experience of an HF diet. The present study reveals systematic alterations in brain lipid levels upon HF diet analyzed either by lipid class and molecular levels.     

Does intranasal application of zinc sulfate produce anosmia in the mouse? An olfactometric and anatomical study

Mice pre-trained in an olfactometer were tested daily on odor detection and discrimination tasks after irrigation of their olfactory epithelium in each naris with 50 microl of 5% zinc sulfate or saline. Anterograde transport of a wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) conjugate from the epithelium to the olfactory bulb was used to assess anatomical connectivity in these and in mice that were used only for histological analyses. One day after treatment, saline controls performed at high levels of accuracy in detecting vapor from solutions of 5-0.01% ethyl acetate and in an odor discrimination task but most ZnSO4-treated mice performed at chance for 5-30 days before showing recovery. Although dense WGA-HRP reaction product was found in the accessory olfactory bulb, there was little or no evidence for axonal transport to glomeruli of the main olfactory bulb in the first 4-8 days after treatment. These results demonstrate that intranasal application of ZnSO4 to mice produces a brief but essentially total disruption of functional connections from the olfactory epithelium to the main olfactory bulb and a corresponding transient anosmia.