Activation of astrocytes and ischemic damage following the transient focal ischemia

Astrocytes play vital roles not only in the mechanical support of the central nervous system but also in the metabolism of neurotransmitters and in the transfer of nutritive substances to neuron. After ischemic brain injuries, it has been known that gliosis appears around degenerative regions and repairs these regions. Recently, accumulating evidence indicates that overexpression of S-100 protein, astrocyte-derived protein, is detrimental to neuronal cells in various pathological conditions. To confirm the astrocytic activation in cerebral ischemia, we examined immunohistochemical changes in S-100 protein and glial fibrillary acidic protein (GFAP) in the transient focal ischemia. Cerebral infarction determined by hematoxylin-eosin staining was slight on day 1 and further expanded on day 2 and 3. Thereafter, GFAP immunoreactivity was observed in boundary zone of the infarct area at 72 hours after the transient focal ischemia. On the other hand, S-100 protein immunoreactivities were markedly increased at 9 hours after the transient focal ischemia. After the infarct formation, the increase of S-100 immunoreactivity was observed in outside boundary of infarct area. These results suggest that astrocytic activation, which we would like to be called "pre-mitotic S-100 peak (PSP)", precedes the neurodegeneration following the transient focal ischemia, and should be distinguished from so-called gliosis observed in the post-neurodegeneration and GFAP-dependent astrocytic proliferation.     

Differentiation of serum-free mouse embryo cells into an astrocytic lineage is associated with the asymmetric production of early neural, neuronal and glial markers

Serum-free mouse embryo (SFME) cells, the astrocyte progenitor cells in the central nervous system (CNS), were exposed to 10 ng/ml leukemia inhibitory factor (LIF) and 10 ng/ml bone morphogenic protein 2 (BMP2) to induce differentiation, and expression of cell-type specific markers. Nestin, a marker of early neural lineage, betaIII-tubulin, a marker of neuronal lineage, oligodendrocyte marker O4 (O4), a marker of oligodendrocytic lineage and glial fibrillary acidic protein (GFAP), a marker of astrocytic lineage, were analyzed. Characteristics of SFME cells, as a CNS progenitor, were identified and a possible mechanism, underlying SFME cell specification into an astrocytic lineage upon differentiation, was investigated. These markers were present, both at the initial proliferative phase and after induction of differentiation. GFAP expression increased strongly upon differentiation, while expression of the other markers changed very little. These results indicate that astrocytic differentiation is associated with the asymmetric production of these markers, rather than through induction of astrocytic markers.     

Development of a neurotoxicity test-system, using human post-mitotic, astrocytic and neuronal cell lines in co-culture.

Astrocytes are essential for neuronal function and survival, so both cell types were included in a human neurotoxicity test-system to assess the protective effects of astrocytes on neurons, compared with a culture of neurons alone. The human NT2.D1 cell line was differentiated to form either a co-culture of post-mitotic NT2.N neuronal (TUJ1, NF68 and NSE positive) and NT2.A astrocytic (GFAP positive) cells (approximately 2:1 NT2.A:NT2.N), or an NT2.N mono-culture. Cultures were exposed to human toxins, for 4h at sub-cytotoxic concentrations, in order to compare levels of compromised cell function and thus evidence of an astrocytic protective effect. Functional endpoints examined included assays for cellular energy (ATP) and glutathione (GSH) levels, generation of hydrogen peroxide (H(2)O(2)) and caspase-3 activation. Generally, the NT2.N/A co-culture was more resistant to toxicity, maintaining superior ATP and GSH levels and sustaining smaller significant increases in H(2)O(2) levels compared with neurons alone. However, the pure neuronal culture showed a significantly lower level of caspase activation. These data suggest that besides their support for neurons through maintenance of ATP and GSH and control of H(2)O(2) levels, following exposure to some substances, astrocytes may promote an apoptotic mode of cell death. Thus, it appears the use of astrocytes in an in vitro predictive neurotoxicity test-system may be more relevant to human CNS structure and function than neuronal cells alone.     

Matrix metalloproteinases 2 and 9 in central nervous system and their modification after vanadium inhalation

Vanadium (V) derivatives are well-known environmental pollutants and its toxicity has been related with oxidative stress. Toxicity after vanadium inhalation on the substantia nigra, corpus striatum, hippocampus and ependymal epithelium was reported previously. The purpose of this study was to analyse the role of matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9) in the changes observed in brain tissue after chronic V inhalation. Mice were exposed to vaporized, vanadium pentoxide 0.02 m in deionized water for 1 h twice a week, and killed at 1 h, 1, 2 and 4 weeks after exposure. The brain was removed and the olfactory bulb, prefrontal cortex, striatum and hippocampus were dissected and the MMP content was obtained by zymography. The results showed that MMP-9 increased in all the structures at the end of the exposure, although in the hippocampus this increment was evident after 1 week of exposure. When MMP-2 was analysed in the olfactory bulb and prefrontal cortex it remained unchanged throughout the whole exposure, while in the hippocampus it increased at week 4, while in the striatum MMP-2 increased from the second week only, through the whole experiment. These results demonstrate that V increased MMPs in different structures of the CNS and this change might be associated with the previously reported modifications, such as dendritic spine loss and neuronal cell death. The modifications in MMPs could be related with blood-brain barrier (BBB) disruption which was reported previously. Oxidative stress might also be involved in the activation of these gelatinases as part of the different mechanisms which take place in V toxicity in the CNS.     

Chronic psychosocial stress and citalopram modulate the expression of the glial proteins GFAP and NDRG2 in the hippocampus

Rationale

It has been suggested that there are causal relationships between alterations in brain glia and major depression.

Objectives

To investigate whether a depressive-like state induces changes in brain astrocytes, we used chronic social stress in male rats, an established preclinical model of depression. Expression of two astrocytic proteins, the intermediate filament component glial fibrillary acidic protein (GFAP) and the cytoplasmic protein N-myc downregulated gene 2 (NDRG2), was analyzed in the hippocampus. For comparison, expression of the neuronal protein syntaxin-1A was also determined.

Methods

Adult male rats were subjected to daily social defeat for 5 weeks and were concomitantly treated with citalopram (30 mg/kg/day, via the drinking water) for 4 weeks.

Results

Western blot analysis showed that the chronic stress downregulated GFAP but upregulated NDRG2 protein. Citalopram did not prevent these stress effects, but the antidepressant per se downregulated GFAP and upregulated NDRG2 in nonstressed rats. In contrast, citalopram prevented the stress-induced upregulation of the neuronal protein syntaxin-1A.

Conclusions

These data suggest that chronic stress and citalopram differentially affect expression of astrocytic genes while the antidepressant drug does not prevent the stress effects. The inverse regulation of the cytoskeletal protein GFAP and the cytoplasmic protein NDRG2 indicates that the cells undergo profound metabolic changes during stress and citalopram treatment. Furthermore, the present findings indicate that a 4-week treatment with citalopram does not restore normal glial function in the hippocampus, although the behavior of the animals was normalized within this treatment period, as reported previously.     

Nanostructures of hydrated C60 fullerene (C60HyFn) protect rat brain against alcohol impact and attenuate behavioral impairments of alcoholized animals

It is well known that chronic ethyl alcohol (EtOH) consumption is capable to injure brain cells and to cause essential abnormalities in behavioral characteristics of animals addicted to alcohol. In this work we for the first time have shown that administration of aqueous solutions of hydrated C60 fullerenes (C60HyFn) with C60 concentration of 30nM as a drinking water during chronic alcoholization of rats (a) protects the tissues of central nervous system (CNS) from damage caused by oxidative stress with high efficacy, (b) prevents the pathological loss of both astrocytes (the main cells of CNS) and astrocytic marker, glial fibrillary acidic proteins (GFAP) and, as consequence, (c) due to their adaptogenic effects, C60HyFn significantly improves behavioral response and eliminates emotional deficits induced by chronic alcohol uptake. The wide range of beneficial biological effects, zero-toxicity, and efficacy even in super-small doses provide a rationale for the possible application of C60HyFn for the treatment of alcohol-induced encephalopathy as well as alcoholism prophylaxis.     

Increase of glial fibrillary acidic protein and S-100B in hippocampus and cortex of diabetic rats: effects of vitamin E

Glial interactions with neurones play vital roles during the ontogeny of the nervous system and in the adult brain. Physical and metabolic insults cause rapid changes in the glial cells and this phenomenon is called reactive gliosis. One of the important events during astrocyte differentiation is the increased expression of glial markers, glial fibrillary acidic protein (GFAP) and S-100B protein. Diabetes mellitus is the most common serious metabolic disorder, which is characterised by functional and structural changes in the peripheral as well as in the central nervous system. In the present study, we aimed to investigate glial reactivity in hippocampus, cortex and cerebellum of streptozotocin-induced diabetic rats by determining the expression of GFAP and S-100B and also to examine the protective effects of vitamin E against gliosis. Western blotting showed increases in total and degraded GFAP content and S-100B protein expression in brain tissues of diabetic rats compared with those of controls. In addition, there was a significant increase in lipid peroxidation in these brain regions of diabetic rats. Both glial markers and lipid peroxidation levels were reversed by vitamin E administration. These findings indicate that streptozotocin-induced diabetes alters degradation and production of GFAP and S-100B, which are markers of reactive astrocytosis. Thus, determination of GFAP and S-100B may provide a relevant marker in the central nervous system for studying neurodegenerative changes in experimental diabetes mellitus. This study also suggests that the gliosis that occurs in diabetes mellitus is mediated, at least indirectly, by free radical formation and antioxidants may prevent reactive gliosis possibly by reducing damaging effects of reactive oxygen species in the central nervous system.     

REACTIVE ASTROCYTIC RESPONSE AND INCREASED PROLIFERATING CELL NUCLEAR ANTIGEN EXPRESSION IN CEREBRAL CORTEX OF ENVENOMED RATS

The regional distribution and the appearance of astrocytes expressing glial fibrillary acidic protein (GFAP), S100 protein, and proliferating cell nuclear antigen (PCNA) were determined in the cerebral cortex of normal and cobra venom intoxicated rats. Male rats were divided to three groups intramuscularly treated with a single injection of either physiological saline solution or ½ LD50 or LD50 of cobra venom respectively. Formalin-fixed paraffin-embedded brain sections of animals of the three groups were immunohistochemically studied according to avidin-biotin-peroxidase complex method using antibodies against GFAP, S100 protein and PCNA. As biomarkers of cerebral neurotoxicity, dose and time dependent increases in the expression of GFAP and S100 protein were observed. Marked increases in the expression of GFAP and S100 protein were common in high dose (LD50) envenomed rats 72 h after venom injection, whereas in low dose (½ LD50) envenomed rats only moderate increases of these two proteins were detected 72 h post-treatment.

Similar pattern of expression was also observed for PCNA in the cerebral cortex layer III but not in layer II or layer I. PCNA, the indicator of cell proliferation, was highly expressed in cerebral cortex of envenomed rats if compared with control animals.

These results demonstrate that intramuscular injection of cobra venom produces enhanced cell proliferation as measured by PCNA staining, and reactive astrocytosis as ascertained by increased GFAP and S100 immunoreactivities. This may represent a protective response of the cerebral cortex by which the brain is able to remove injured cells and protect the remaining neurons by PCNA expression. Furthermore, these observations affirm the usefulness of GFAP, S100 and PCNA immunohistochemistry as a sensitive biomarker of neurotoxicity.     

Chronic cerebral hypoperfusion-induced neuropathological changes in rats.

We investigated the time courses of histopathological changes in various brain regions following permanent occlusion of the bilateral common carotid arteries (2VO) in rats. 2VO rats exhibited rarefaction in the white matter, shrinkage of neurons in the cerebral cortex and hippocampus CA1-3 and dentate gyrus areas 1-3 days after the operation. These histological changes in the cortex and hippocampus were accompanied by a decrease in immunoreactivity for microtubule-associated protein 2 (MAP2), a marker protein of neuronal dendrites. Immunoreactivity for glial fibrillary acid protein (GFAP) was observed at 3-7 days after the 2VO operation. A marked increase in GFAP staining of the astrocytes in the cerebral cortex and hippocampus was found 30 days after ligation. Eight-arm radial maze performance was tested from 14 days to 60 days after the operation. The 2VO rats showed fewer initial correct responses than sham-operated control rats during a repeated training period. These findings suggested that the loss in dendritic MAP2 immunoreactivity and an increase in astroglial staining and/or rarefaction of the white matter may cause neuronal death, infarction and learning impairment under conditions of chronic hypoperfusion.     

A dose-response study of ibogaine-induced neuropathology in the rat cerebellum.

Ibogaine (IBO) is an indole alkaloid from the West African shrub, Tabernanthe iboga. It is structurally related to harmaline, and both these compounds are rigid analogs of melatonin. IBO has both psychoactive and stimulant properties. In single-blind trials with humans, it ameliorated withdrawal symptoms and interrupted the addiction process. However, IBO also produced neurodegeneration of Purkinje cells and gliosis of Bergmann astrocytes in the cerebella of rats given even a single dose (100 mg/kg, ip). Here, we treated rats (n = 6 per group) with either a single ip injection of saline or with 25 mg/kg, 50 mg/kg, 75 mg/kg, or 100 mg/kg of IBO. As biomarkers of cerebellar neurotoxicity, we specifically labeled degenerating neurons and axons with silver, astrocytes with antisera to glial fibrillary acidic protein (GFAP), and Purkinje neurons with antisera to calbindin. All rats of the 100-mg/kg group showed the same pattern of cerebellar damage previously described: multiple bands of degenerating Purkinje neurons. All rats of the 75-mg/ kg group had neurodegeneration similar to the 100-mg/kg group, but the bands appeared to be narrower. Only 2 of 6 rats that received 50 mg/kg were affected; despite few degenerating neuronal perikarya, cerebella from these rats did contain patches of astrocytosis similar to those observed with 75 or 100 mg/kg IBO. These observations affirm the usefulness of GFAP immunohistochemistry as a sensitive biomarker of neurotoxicity. None of the sections from the 25-mg/kg rats, however stained, were distinguishable from saline controls, indicating that this dose level may be considered as a no-observable-adverse-effect level (NOAEL).     

Vanadium (V)-Induced Neurotoxicity in the Rat Central Nervous System: A Histo-Immunohistochemical Study

As vanadium was found to induce oxidative stress in the central nervous system, the morphological alterations of neurons and astroglial cells in adult rat central nervous system after vanadium exposure was studied, using histological markers of cellular injury. Animals were intraperitoneally injected with 3 mg/kg body weight of sodium metavanadate for 5 consecutive days. NADPH diaphorase histochemistry and heat shock protein (hsp) 70, glial fibrillary acidic protein (GFAP), and S-100 immunohistochemistry were performed in floating sections of several brain areas. NADPHd staining was higher in the molecular and granular layers of the cerebellar cortex, and small NADPHd-stained interneurons were observed in hippocampal sections in V(+5)-exposed animals. hsp 70 immunostaining showed the presence of reactive neurons in cerebellum of treated animals. GFAP and S-100 immunohistochemistry showed enlarged astrocytes in cerebellum and hippocampus in the V(+5)-exposed animals. The histological markers used showed that the main areas affected by vanadium-mediated free-radical generation were the hippocampus and the cerebellum.     

Vanadium (V)-induced neurotoxicity in the rat central nervous system: a histo-immunohistochemical study

As vanadium was found to induce oxidative stress in the central nervous system, the morphological alterations of neurons and astroglial cells in adult rat central nervous system after vanadium exposure was studied, using histological markers of cellular injury. Animals were intraperitoneally injected with 3 mg/kg body weight of sodium metavanadate for 5 consecutive days. NADPH diaphorase histochemistry and heat shock protein (hsp) 70, glial fibrillary acidic protein (GFAP), and S-100 immunohistochemistry were performed in floating sections of several brain areas. NADPHd staining was higher in the molecular and granular layers of the cerebellar cortex, and small NADPHd-stained interneurons were observed in hippocampal sections in V(+5)-exposed animals. hsp 70 immunostaining showed the presence of reactive neurons in cerebellum of treated animals. GFAP and S-100 immunohistochemistry showed enlarged astrocytes in cerebellum and hippocampus in the V(+5)-exposed animals. The histological markers used showed that the main areas affected by vanadium-mediated free-radical generation were the hippocampus and the cerebellum.     

Reactive astrocytic responses to denervation in the motor cortex of adult rats are sensitive to manipulations of behavioral experience

Recent research has suggested that mild denervation of the neocortex of adult rats may facilitate neuronal growth in response to behavioral changes. Astrocytes react to denervation, produce growth-promoting factors and are a potential mediator of this denervation-facilitated growth. The present study assessed whether astrocytic reactions to denervation vary dependent upon post-injury behavioral experience. Denervation of the transcallosal afferents to the motor cortex was induced via partial transections of the corpus callosum. Transected- or sham-operated rats were then either forced to use the opposite forelimb (via limb-restricting vests) or permitted to use both forelimbs normally for 8 days. In the motor cortex, the surface density of glial fibrillary acidic protein (GFAP)-immunoreactive (IR) astrocytic processes and the density of basic fibroblast growth factor (FGF-2)-IR glial cells was significantly increased as a result of transections alone and as a result of forced forelimb-use alone in comparison to controls. The combination of transections and forced-use significantly enhanced GFAP-IR in comparison to all other groups, but did not further enhance FGF-2-IR. These findings are consistent with behavior and denervation having interactive influences on astrocytic reactivity in the motor cortex. These results also raise the possibility that astrocyte-mediated support of neural restructuring after brain injury might be enhanced with appropriate post-injury behavioral manipulations.     

Astroglial reaction during the early phase of acute lead toxicity in the adult rat brain

The developing nervous system is susceptible to lead (Pb) exposure but less is known about the effect of this toxic agent in adult rat brain. Since astrocytes serve as a cellular Pb deposition site, it is of importance to investigate the response of astroglial cells in the adult rat brain in a model of acute lead exposure (25 mg/kg b.w. of lead acetate, i.p. for 3 days). An increased immunoreactivity of glial fibrillary acidic protein (GFAP) on Western blots was noticeable in fractions of astroglial origin-glial plasmalemmal vesicles (GPV) and in homogenates from the hippocampus and cerebral cortex but not in the cerebellum. The features of enhanced astrocytic reactivity (i.e. large accumulation of mitochondria, activated Golgi apparatus and increment of gliofilaments) were observed in electron microscopy studies in the same tissues. Total glutathione levels increased both in GPV fractions and in brain homogenates-in the cerebellum (120% above control) and in hippocampus (30% above control). The results of current studies indicate that acute lead exposure is accompanied by astrocyte activation connected with the presence of the enhanced expression of GFAP. It may indicate lead-induced neuronal injury. At the same time, a regional enhancement of detoxicative mechanisms (GSH) was noticed, suggesting activation of astrocyte-mediated neuroprotection against toxic Pb action.     

哌替啶不同给药时程对SD大鼠齿状回星形胶质细胞形态和GFAP表达的影响

目的 观察哌替啶不同给药时程对SD大鼠齿状回星形胶质细胞形态和胶质纤维酸性蛋白(GFAP)表达的影响.方法 成年SD大鼠24只随机分为对照(C)组、单次给药1d处死(D1)组、重复给药7 d处死(D7)组和重复给药14 d处死(D14)组.各组在末次给药24 h后经心脏灌注取脑.免疫组化检测GFAP,共聚焦显微镜观察、测定齿状回GFAP阳性星形胶质细胞的数量及体视学参数.结果 D1组GFAP表达水平增加,平均细胞面积减小,细胞个数增加,细胞形态复杂,侧枝增多;D7组GFAP表达水平较D1组有所下降,但仍高于C组,细胞的侧枝开始减少;而D14组GFAP表达水平与C组相仿,细胞胞体皱缩,面积缩小,侧枝更少.结论 哌替啶不同给药时程对SD大鼠齿状回星形胶质细胞形态和GFAP表达的影响不尽相同.     

Intranasal instillation of aflatoxin B(1) in rats: bioactivation in the nasal mucosa and neuronal transport to the olfactory bulb.

Aflatoxin B(1) (AFB(1)) may be present in moldy dust. Inhalation of contaminated dust particles may result in high local exposure of the nasal mucosa. The present study was designed to assess bioactivation and toxicity of AFB(1) in the nasal mucosa after intranasal administration of the mycotoxin in rats and also to examine if translocation of the mycotoxin occurs from the nasal mucosa to the brain along olfactory neurons. Female Sprague-Dawley rats were given (3)H-AFB(1) (0.2, 1 or 20 microg) intranasally and were sacrificed at various intervals (1 h to 20 d). Tissues were examined autoradiographically or histopathologically. Quantitative data were obtained by beta-spectrometry in rats given (3)H-AFB(1) intranasally or orally (for comparison). The data indicated that intranasal administration of AFB(1) resulted in formation of tissue-bound metabolites in sustentacular cells, in some cells of Bowman's glands, and in a population of neuronal cells in the olfactory mucosa, whereas in the respiratory nasal mucosa, there was selective bioactivation of AFB(1) in mucous cells. Intranasal instillation of 20 microg AFB(1) resulted in disorganized undulating olfactory epithelium, with injured neuronal and sustentacular cells. In the respiratory epithelium, there was selective destruction of mucous cells. beta-Spectrometry and autoradiography with tape-sections of the head of rats given (3)H-AFB(1) intranasally indicated transport of AFB(1) and/or AFB(1) metabolites along the axons of the primary olfactory neurons to their terminations in the glomeruli of the olfactory bulb. The data indicate that the materials transported in the olfactory nerves represent AFB(1) and/or some of its nonreactive metabolites. It is concluded that application of AFB(1) on the nasal mucosa in rats results in high local bioactivation of the mycotoxin in this tissue and translocation of AFB(1) and/or its metabolites to the olfactory bulb.     

Nasal toxicity of manganese sulfate and manganese phosphate in young male rats following subchronic (13-week) inhalation exposure

Growing evidence suggests that nasal deposition and transport along the olfactory nerve represents a route by which inhaled manganese and certain other metals are delivered to the rodent brain. The toxicological significance of olfactory transport of manganese remains poorly defined. In rats, repeated intranasal instillation of manganese chloride results in injury to the olfactory epithelium and neurotoxicity as evidenced by increased glial fibrillary acidic protein (GFAP) concentrations in olfactory bulb astrocytes. The purpose of the present study was to further characterize the nasal toxicity of manganese sulfate (MnSO(4)) and manganese phosphate (as hureaulite) in young adult male rats following subchronic (90-day) exposure to air, MnSO(4) (0.01, 0.1, and 0.5 mg Mn/m(3)), or hureaulite (0.1 mg Mn/m(3)). Nasal pathology, brain GFAP levels, and brain manganese concentrations were assessed immediately following the end of the 90-day exposure and 45 days thereafter. Elevated end-of-exposure olfactory bulb, striatum, and cerebellum manganese concentrations were observed following MnSO(4) exposure to > or = 0.01, > or = 0.1, and 0.5 mg Mn/m(3), respectively. Exposure to MnSO(4) or hureaulite did not affect olfactory bulb, cerebellar, or striatal GFAP concentrations. Exposure to MnSO(4) (0.5 mg Mn/m(3)) was also associated with reversible inflammation within the nasal respiratory epithelium, while the olfactory epithelium was unaffected by manganese inhalation. These results confirm that high-dose manganese inhalation can result in nasal toxicity (irritation) and increased delivery of manganese to the brain; however, we could not confirm that manganese inhalation would result in altered brain GFAP concentrations.     

Monocrotaline pyrrol is cytotoxic and alters the patterns of GFAP expression on astrocyte primary cultures.

Dehydromonocrotaline (DHMC) is the main monocrotaline active cytochrome P450's metabolite, and has already been assessed in the CNS of experimentally intoxicated rats. DHMC effects were here investigated toward rat astroglial primary cultures regarding cytotoxicity, morphological changes and regulation of GFAP expression. Cells, grown in DMEM supplemented medium, were treated with 0.1-500 microM DHMC, during 24- and 72-h. According to MTT and LDH tests, DHMC was toxic to astrocytes after 24-h exposure at 1 microM, and induced membrane damages at 500 microM. Rosenfeld dying showed hypertrophic astrocytes after 72-h exposure to 0.1-1 microM DHMC. GFAP immunocytochemistry and western immunoblot revealed an increase of GFAP labelling and expression, suggesting an astrogliotic reaction to low concentrations of DHMC. At higher concentrations (10-500 microM), astrocytes shrank their bodies and retracted their processes, presenting a more polygonal phenotype and a weaker expression on GFAP labelling Nuclear chromatin staining by Hoechst-33258 dye, revealed condensed and fragmented chromatin in an important proportion (+/-30%) of the astrocytes exposed to 100-500 microM DHMC, suggesting signs of apoptosis. Our results confirm a cytotoxic and dose-dependent effect of DHMC on cultures of rat cortical astrocytes, leading to apoptotic figures. These effects might be related to the neurological damages and clinical signs observed in animals intoxicated by Crotalaria.     

Accumulation of Cd(II) in the CNS Depending on the Route of Administration: Intraperitoneal, Intratracheal, or Intranasal

The uptake and subsequent neuronal transport of certain heavymetals in the olfactory mucosa may be a major means by whichthese compounds gain access to the CNS. To contrast olfactoryversus blood-borne routes of exposure, three groups (n = 4)of adult Long-Evans rats were exposed to solutions of radiolabeledCdCl₂. Exposure was by one of three routes: unilateral intranasalinstillation (IN), intratracheal lavage (IT), or intraperitonealinjection (ip). The dose level for the intranasal route was30 µl of 1 µM CdCl₂ labeled with 1 µCi ¹⁰⁹Cd.For IT and ip, the dose was 30 µl of 1 µM CdCl₂diluted to 300 µl in saline and labeled with 1 µCi¹⁰⁹Cd. Rats were euthanized 24 hr after exposure, tissue sampleswere taken, and radioactivity was counted. Cd levels were lowin the olfactory bulbs of rats exposed either intratracheallyor intraperitoneally. However, in rats intranasally exposed,Cd levels were nearly 40 higher in olfactory bulbs ipsilateralto the exposed side than in those on the contralateral side.With all routes of exposure, Cd levels in brain samples wereonly slightly elevated. These results suggest that for certainairborne toxicants, especially those that are excluded fromthe CNS by the blood-brain barrier, the olfactory system mayprovide a direct route of entry into the CNS.     

甲基苯丙胺的神经毒性及对GFAP表达的研究

目的探讨甲基苯丙胺(MA)的神经毒性及胶质纤维酸性蛋白(GFAP)的表达。方法设立对照组和实验组,实验组予MA,对照组予等体积生理盐水。采用HPLC测定不同脑区DA和5-HT的含量,用免疫组织化学方法检测GFAP的表达。结果给予MA后,大鼠额叶皮层和纹状体的5-HT和DA均有下降;但对海马DA的影响不明显,对GFAP蛋白的表达明显上调。结论MA对中枢5-HT、DA系统具有明显的神经毒性,并导致GFAP表达的上调。