Airborne manganese exposure differentially affects end points of oxidative stress in an age-and sex-dependent manner

Juvenile female and male (young) and 16-mo-old male (old) rats inhaled manganese in the form of manganese sulfate (MnSO₄) at 0, 0.01, 0.1, and 0.5 mg Mn/m³ or manganese phosphate at 0.1 mg Mn/m³ in exposures of 6h/d, 5d/wk for 13 wk. We assessed biochemical end points indicative of oxidative stress in five brain regions: cerebellum, hippocampus, hypothalamus, olfactory bulb, and striatum. Glutamine synthetase (GS) protein levels, metallothionein (MT) and GS mRNA levels, and total glutathione (GSH) levels were determined for all five regions. Although most brain regions in the three groups of animals were unaffected by manganese exposure in terms of GS protein levels, there was significantly increased protein (p<0.05) in the hippocampus and decreased protein in the hypothalamus of young male rats exposed to manganese phosphate as well as in the aged rats exposed to 0.1 mg/m³ MnSO₄. Conversely, GS protein was elevated in the olfactory bulb of females exposed to the high dose of MnSO₄. Statistically significant decreases (p<0.05) in MT and GS mRNA as a result, of manganese exposure were observed in the cerebellum, olfactory bulb, and hippocampus in the young male rats, in the hypothalamus in the young female rats, and in the hippocampus in the senescent males. Total GSH levels significantly (p<0.05) decreased in the olfactory bulb of manganese exposed young male rats and increased in the olfactory bulb of female rats exposed to manganese. Both the aged and young female rats had significantly decreased (p<0.05) GSH in the striatum resulting from manganese inhalation. The old male rats also had depleted GSH levels in the cerebellum and hypothalamus as a result, of the 0.1-mg/m³ manganese phosphate exposure. These results demonstrate that age and sex are variables that must be considered whenassessing the neurotoxicity of manganese.     

Oxidative stress is induced in the rat brain following repeated inhalation exposure to manganese sulfate

Eight-week-old rats inhaled manganese (Mn) in the form of MnSO₄ at 0, 0.03, 0.3, or 3.0 mg Mn/m³ for 6 h/d for 7 d/wk (14 consecutive exposures). Brain manganese concentrations in these animals were reported by Dorman et al. in 2001, noting the following rank order: olfactory bulb>striatum>cerebellum. We assessed biochemical end points indicative of oxidative stress in these three brain regions, as well as the hypothalamus and hippocampus. Glutamine synthetase (GS) protein levels and total glutathione (GSH) levels were determined for all five regions. GS mRNA and metallothionein (MT) mRNA levels were also evaluated for the cerebellum, hypothalamus, and hippocampus. Statistically significant increases (p<0.05) in GS protein were observed in the olfactory bulb upon exposure to the medium and high manganese doses. In the hypothalamus, statistically significant (p<0.05) but more modest increases were also noted in the medium and high manganese dose. Total GSH levels significantly (p<0.05) decreased only in the hypothalamus (high manganese dose), and MT mRNA significantly increased in the hypothalamus (medium manganese dose). No significant changes were noted in any of the measured parameters in the striatum, although manganese concentrations in this region were also increased. These results demonstrate that the olfactory bulb and hypothalamus represent potentially sensitive areas to oxidative stress induced by exceedingly high levels of inhaled manganese sulfate and that other regions, and especially the striatum, are resistant to manganese-induced oxidative stress despite significant accumulation of this metal.     

Alterations of oxidative stress biomarkers due to in utero and neonatal exposures of airborne manganese

Neonatal rats were exposed to airborne manganese sulfate (MnSO₄) (0, 0.05, 0.5, or 1.0 mg Mn/m³) during gestation (d 0–19) and postnatal days (PNDs) 1–18. On PND19, rats were killed, and we assessed biochemical end points indicative of oxidative stress in five brain regions: cerebellum, hippocampus, hypothalamus, olfactory bulb, and striatum. Glutamine synthetase (GS) and tyrosine hydroxylase (TH) protein levels, metallothionein (MT), TH and GS mRNA levels, and reduced and oxidized glutathione (GSH and GSSG, respectively) levels were determined for all five regions. Mn exposure (all three doses) significantly (p=0.0021) decreased GS protein levels in the cerebellum, and GS mRNA levels were significantly (p=0.0008) decreased in the striatum. Both the median and high dose of Mn significantly (p=0.0114) decreased MT mRNA in the striatum. Mn exposure had no effect on TH protein levels, but it significantly lowered TH mRNA levels in the olfactory bulb (p=0.0402) and in the striatum (p=0.0493). Mn eposure significantly lowered GSH levels at the median dose in the olfactory bulb (p=0.032) and at the median and high dose in the striatum (p=0.0346). Significantly elevated (p=0.0247) GSSG, which can be indicative of oxidative stress, was observed in the cerebellum of pups exposed to the high dose of Mn. These data reveal that alterations of oxidative stress biomarkers resulting from in utero and neonatal exposures of airborne Mn exist. Coupled with our previous study in which similarly exposed rats were allowed to recover from Mn exposure for 3 wk, it appears that many of these changes are reversible. It is important to note that the doses of Mn utilized represent levels that are a hundred- to a thousand-fold higher than the inhalation reference concentration set by the United States Environmental Protection Agency.     

Regional distribution of metallothionein, zinc, and copper in the brain of different strains of rats

The regional brain distribution of metallothionein (MT), zinc, and copper in the brain was determined in nine anatomical regions (olfactory bulb, cortex, corpus striatum, hippocampus, thalamus plus hypothalamus, pons plus medulla oblongata, cerebellum, midbrain, and white matter) and was compared between two different strains of rat (Sprague-Dawley [SD] and Lewis). No significant difference was observed in the whole-brain MT level between the two strains (17.8 ± 3.4 μg/g in SD rats and 20.3 ± 2.3 μg/g in Lewis rats). In SD rats, however, MT was more highly expressed in the white matter than in the other regions studied. In contrast, MT concentration was highest in the cortex and lowest in the olfactory bulb in Lewis rats. The MT levels in the cortex, corpus striatum, hippocampus, and thalamus plus hypothalamus were significantly lower in SD rats than in Lewis rats. In both strains, the olfactory bulb contained markedly higher levels of both zinc and copper than the other regions (27.9 ±6.8 μg/g zinc in SD rats and 27.6 ± 6.9 μg/g zinc in Lewis rats, and 5.2 ± 1.5 μg/g copper in SD rats and 11.1 ± 4.8 μg/g copper in Lewis rats). The next high-est zinc levels were seen in the hippocampus, whereas the next highest copper levels were in the corpus striatum in both SD and Lewis rats. The high levels of zinc and copper in the olfactory bulb were not accompanied by concomitant high MT concentrations. These results indicate that the strain of rat as well as the anatomical brain region should be taken into account in MT and metal distribution studies. However, the highest concentrations of zinc and copper in olfactory bulb were common to both SD and Lewis rats. The discrepancy between MT and the metal levels in olfactory bulb suggests a role for other proteins in addition to MT in the homeostatic control of zinc and copper.     

Effects of acute manganese chloride exposure on lipid peroxidation and alteration of trace metals in rat brain

Although manganese (Mn) is an essential element, exposure to excessive levels of Mn and its accumulation in the brain can cause neurotoxicity and extrapyramidal syndrome. We have investigated the differences in the accumulated levels of Mn, the degree of lipid peroxidation, and its effects on the levels of trace elements (Fe, Cu, and Zn) in various regions in the brain of rats having undergone acute Mn exposure. The rats in the dose—effect group were injected intraperitoneally (ip) with MnCl₂ (25, 50, or 100 mg MnCl₂/kg) once a day for 24 h. The Mn significantly accumulated (p<0.05) in the frontal cortex, corpus callosum, hippocampus, striatum, hypothalamus medulla, cerebellum, and spinal cord in each case. The rats in the timecourse group were ip injected with MnCl₂ (50 mg MnCl₂/kg) and then monitored 12, 24, 48, and 72 h after exposure. The Mn accumulated in the frontal cortex, corpus callosum, hippocampus, striatum hypothalamus, medulla, cerebellum, and spinal cord after these periods of time, In both the dose—effect and time-course studies, we observed that the concentration of malondialdehyde, an end product of lipid peroxidation, increased significantly in the frontal cortex, hippocampus, striatum, hypothalamus, medulla, and cerebellum. However, no relationship between the concentrations of Mn in the brain and the extent of lipid peroxidation was observed. In addition, we found that there was a significant increase (p<0.05) in the level of Fe in the hippocampus, striatum, hypothalamus, medulla, and cerebellum, but the Cu and Zn levels had not changed significantly. These findings indicated that Mn induces an increase in the iron level, which provides direct evidence for Fe-mediated lipid peroxidation in the rats' brains; these phenomena might play important roles in the mechanisms of Mn-induced neurotoxicology.     

Effect of Chronic Manganese Treatment on Adenosine Tissue Levels and Adenosine A2a Receptor Binding in Diverse Regions of Mouse Brain

In the present study the effects of chronic manganese (Mn) treatment on adenosine A_2a receptor binding in mouse brain have been assessed. Male albino mice were divided in two groups: In the Mn-treated group, the animals were injected intraperitoneally (i.p.) with MnCl₂ (5 mg/kg/day) five days per week during 9 weeks; in the control group, they were injected likewise with a saline solution. A significant decrease of the Kd without alteration of Bmax in the cerebellum and, an increase of the Kd and Bmax in hippocampus of mice treated with Mn were found. Also, an increase of Kd in frontal cortex was observed. The binding parameters in caudate nucleus, olfactory bulb and hypothalamus were not altered by Mn. A significant decrease in the adenosine concentration in caudate nucleus, olfactory bulb and hypothalamus, without significant changes in hippocampus, frontal cortex and cerebellum was also detected. These findings suggest that chronic administration of Mn could affect adenosine receptor function and turnover, depending on the brain region analyzed.     

Desipramine administered chronically inhibits lipopolysaccharide-stimulated production of IL-1β in the brain and plasma of rats

Nowadays, it is assumed that therapeutic efficacy of antidepressants depends, at least partly, on their anti-inflammatory properties. The present study investigated for the first time the effect of 21-day oral administration of desipramine on the lipopolysaccharide (LPS)-stimulated IL-1β concentration in the olfactory bulb, hypothalamus, frontal cortex, hippocampus and plasma of rats, and on the LPS-induced IL-1β mRNA level in the olfactory bulb. Desipramine (15 mg/kg/day) reduced significantly the LPS (250 μg/kg i.p.)-induced IL-1β concentration in the olfactory bulb, hypothalamus and in plasma, and diminished the LPS effect on IL-1β mRNA in the olfactory bulb. Plasma concentration of desipramine was comparable to its therapeutic range. By using the α1/α2-adrenoceptor antagonist prazosin and the unspecific β-adrenoceptor antagonist propranolol given prior to LPS, we found that the effect of desipramine on LPS-induced IL-1β production was partially mediated by both adrenoceptors in the olfactory bulb and plasma, and that β-adrenoceptors contributed also to its effect on the stimulated IL-1β concentration in the hypothalamus. The effect of LPS on the cerebral IL-1β levels was, in part, mediated by β-adrenoceptors and, in a region-specific manner, by α1/α2-adrenoceptors. The findings provide evidence for central and peripheral anti-inflammatory activity of desipramine and confirm the impact of the noradrenergic system on IL-1β production induced by an immunostimulatory challenge.     

Chronic hypoxia in development selectively alters the activities of key enzymes of glucose oxidative metabolism in brain regions

The immature brain is more resistant to hypoxia/ischemia than the mature brain. Although chronic hypoxia can induce adaptive-changes on the developing brain, the mechanisms underlying such adaptive changes are poorly understood. To further elucidate some of the adaptive changes during postnatal hypoxia, we determined the activities of four enzymes of glucose oxidative metabolism in eight brain regions of hypoxic and normoxic rats. Litters of Sprague-Dawley rats were put into the hypoxic chamber (oxygen level maintained at 9.5%) with their dams starting on day 3 postnatal (P3). Age-matched normoxic rats were use as control animals. In P10 hypoxic rats, lactate dehydrogenase (LDH) activity in cerebral cortex, striatum, olfactory bulb, hippocampus, hypothalamus, pons and medulla, and cerebellum was significantly increased (by 100%–370%) compared to those in P10 normoxic rats. In P10 hypoxic rats, hexokinase (HK) activity in hypothalamus, hippocampus, olfactory bulb, midbrain, and cerebral cortex was significantly decreased (by 15%–30%). Neither -ketoglutarate dehydrogenase complex (KGDHC, which is believed to have an important role in the regulation of the tricarboxylic acid [TCA] cycle flux) nor citrate synthase (CS) activity was significantly decreased in the eight regions of P10 hypoxic rats compared to those in P10 normoxic rats. In P30 hypoxic rats, LDH activity was only increased in striatum (by 19%), whereas HK activity was only significantly decreased (by 30%) in this region. However, KGDHC activity was significantly decreased in olfactory bulb, hippocampus, hypothalamus, cerebral cortex, and cerebellum (by 20%–40%) in P30 hypoxic rats compared to those in P30 normoxic rats. Similarly, CS activity was decreased, but only in olfactory bulb, hypothalamus, and midbrain (by 9%–21%) in P30 hypoxic rats. Our results suggest that at least some of the mechanisms underlying the hypoxia-induced changes in activities of glycolytic enzymes implicate the upregulation of HIF-1. Moreover, our observation that chronic postnatal hypoxia induces differential effects on brain glycolytic and TCA cycle enzymes may have pathophysiological implications (e.g., decreased in energy metabolism) in childhood diseases (e.g., sudden infant death syndrome) in which hypoxia plays a role.     

Excitotoxicity in Rat’s Brain Induced by Exposure of Manganese and Neuroprotective Effects of Pinacidil and Nimodipine

Manganese (Mn) is an essential trace element for humans. However, manganism would be caused by excessive Mn. The mechanisms underlying excitotoxicity induced by manganism are poorly understood. As it is known to us, glutamate (Glu) is the most prevalent excitatory neurotransmitter. To determine the possible role of dysfunction of Glu transportation and metabolism in Mn-induced excitotoxicity, the rats were ip injected with different dose of MnCl₂ (0, 50, 100, and 200 μmol/kg), the levels of Mn and activities of GS, PAG, Na⁺-K⁺-ATPase, and Ca²⁺-ATPase in striatum were investigated. In addition, effect of 20.38 μmol/kg pinacidil (K⁺ channel opener) or 2.4 μmol/kg nimodipine (Ca²⁺ channel blocker) were studied at 200 μmol/kg MnCl₂. With dose-dependent inhibition of GS, Na⁺-K⁺-ATPase, and Ca²⁺-ATPase activities, increase of Mn levels and PAG activity were observed. Further investigation indicated that pre-treatment of pinacidil or nimodipine reversed toxic effect of MnCl₂ significantly. These results suggested that MnCl₂ could induce dysfunction of Glu transportation and metabolism by augmenting the excitotoxicity dose-dependently; pinacidil and nimodipine might antagonize manganese neurotoxicity.     

Regional and cellular codistribution of interleukin 1 beta and nerve growth factor mRNA in the adult rat brain: possible relationship to the regulation of nerve growth factor synthesis

We have found a regional distribution of IL 1 beta mRNA and IL 1 activity in the normal adult rat brain, which reveals at least partially a colocalization with nerve growth factor (NGF). The predominantly neuronal signal patterns were found over the granule cells of the dentate gyrus, the pyramidal cells of the hippocampus, the granule cells of the cerebellum, the granule and periglomerular cells of the olfactory bulb, and over dispersed cells of the ventromedial hypothalamus and of the frontal cortex. In these areas also the highest levels of IL 1 activity were observed. In the striatum and septum much lower levels of IL 1 beta mRNA and IL 1 activity (shown for the striatum), most likely synthesized by glial cells, could be determined. IL 1 beta-expressing cells were mainly found in brain regions that also synthesize NGF mRNA as shown by in situ hybridization. NGF mRNA could be demonstrated over pyramidal cells of the hippocampus, granule cells of the dentate gyrus, periglomerular cells of the olfactory bulb and over prefrontal cortex neurons. These data indicate that IL 1 beta, among other factors, might also play a regulatory role in the synthesis of NGF in the CNS, as has been demonstrated in the peripheral nervous system (Lindholm, D., R. Heumann, M. Meyer, and H. Thoenen. 1987. Nature (Lond.). 330:658-659).     

The effects of acute ethanol exposure and ageing on rat brain glutathione metabolism

Abstract

Binge alcohol consumption in adolescents is increasing, and it has been proposed that immature brain deals poorly with oxidative stress. The aim of our work was to study the effect of an acute dose of ethanol on glutathione (GSH) metabolism in frontal cortex, hippocampus and striatum of juvenile and adult rats. We have observed no change in levels of glutathione produced by acute alcohol in the three brain areas studied of juvenile and adult rats. Only in the frontal cortex the ratio of GSH/GSSG was increased in the ethanol-treated adult rats. GSH levels in the hippocampus and striatum were significantly higher in adult animals compared to young ones. Higher glutathione peroxidase (GPx) activity in adult rats was observed in frontal cortex and in striatum. Our data show an increased GSH concentration and GPx activity in different cerebral regions of the adult rat, compared to the young ones, suggesting that age-related variations of total antioxidant defences in brain may predispose young brain structures to ethanol-induced, oxidative stress-mediated tissue damage.     

Polysialic Acid Synthase (ST8Sia II/STX) mRNA Expression in the Developing Mouse Central Nervous System

Abstract: A comparative study was undertaken to correlate the immunohistochemical localization of polysialic acid (PSA) and the in situ localization of ST8Sia II mRNA. In situ hybridization of postnatal day 3 mouse brain showed high levels of ST8Sia II mRNA expression in the cerebral neocortex, striatum, hippocampus, subiculum, medial habenular nucleus, thalamus, pontine nuclei, and inferior colliculus; intermediate-level expression in the olfactory bulb, hypothalamus, superior colliculus, and cerebellum; and low-level expression in other regions. The distribution of ST8Sia II mRNA in the neocortex and cerebellum coincided with the immunohistochemical localization of PSA. During brain development, ST8Sia II mRNA started decreasing and had almost disappeared by postnatal day 14. Comparison between ST8Sia II and IV mRNA expression was also undertaken by northern blot analysis and competitive PCR analysis. During the late embryonic to early postnatal stages of the mouse CNS, the ST8Sia II mRNA showed abundant mRNA expression compared with the ST8Sia IV mRNA. Competitive PCR analysis of the adult mouse CNS showed weak expression of the two genes in the olfactory bulb, thalamus, hippocampus, and eyes. The regional and transient expression of ST8Sia II mRNA coincides with that of PSA, suggesting that ST8Sia II is closely involved in the biosynthesis and expression of PSA in the developing mouse CNS.     

Regionally specific effects of diazepam on brain serotonin metabolism in rats: Sustained effects following repeated administration

The effects of single (1mg/kg) and repeated (1mg/kg 2¹ daily for 4 days) diazepam administration are investigated on brain regional 5-hydroxytryptamine (5-HT; serotonin) and 5-hydroxy indoleacetic acid (5-HIAA) concentration in rats. Daily treatment decreased food intakes but body weights did not decrease. Administration of diazepam (1mg/kg) to 4 day sahne injected rats on the 5th day decreased 5-HT levels in the hippocampus and increased it in the hypothalamus. 5-HIAA levels were increased in the striatum and decreased in the hypothalamus. 4 day diazepam injected rats injected with sahne on the 5th day also exhibited silmilar changes of 5-HT and 5-HIAA. Cortical levels of 5-HIAA were also smaller in these rats. Administration of diazepam to 4 day diazepam injected rats again decreased 5-HT in the hippocampus and 5-HIAA in the hypothalamus. 5-HT and 5-HIAA were both decreased in the striatum. Regionally specific effects of diazepam on brain serotonin metabolism are discussed in relation to their possible functions.     

Regional Distribution of the GABAA/Benzodiazepine Receptor (α Subunit) mRNA in Rat Brain

A human cDNA clone containing the 5' coding region of the GABAA/benzodiazepine receptor alpha subunit was used to quantify and visualize receptor mRNA in various regions of the rat brain. Using a [32P]CTP-labelled antisense RNA probe (860 bases) prepared from the alpha subunit cDNA, multiple mRNA species were detected in Northern blots using total and poly A rat brain RNA. In all brain regions, mRNAs of 4.4 and 4.8 kb were observed, and an additional mRNA of 3.0 kb was detected in the cerebellum and hippocampus. The level of GABAA/benzodiazepine receptor mRNA was highest in the cerebellum followed by the thalamus = frontal cortex = hippocampus = parietal cortex = hypothalamus much greater than pons = striatum = medulla. In situ hybridization revealed high levels of alpha subunit mRNA in cerebellar gray matter, olfactory bulb, thalamus, hippocampus/dentate gyrus, and the arcuate nucleus of the hypothalamus. These data suggest the presence of multiple GABAA/benzodiazepine receptor alpha subunit mRNAs in rat brain and demonstrate the feasibility of studying the expression of genes encoding the GABAA/benzodiazepine receptor after pharmacological and/or environmental manipulation.     

Cocaine

Cocaine HCl (0, 10, or 50 mg/kg) was injected into adult male ICR mice ip. Thirty minutes later, the brains were removed, and nine regions were isolated: olfactory bulbs, olfactory tubercles, prefrontal cortex, septum, striatum, amygdala, hypothalamus, hippocampus, and thalamus. Using high-performance liquid chromatography, concentrations of norepinephrine, dopamine, serotonin, and their major metabolites and the metabolite/neurotransmitter ratios were determined as an indicator of utilization. Serotonergic systems responded most dramatically. 5HIAA/5-HT decreases were seen in all the brain regions, except the septum, hippocampus, and olfactory bulbs. In most instances, the alterations were dose-dependent. The most profound changes were seen in the amygdala, prefrontal cortex, hypothalamus, and thalamus. For noradrenergic systems, significant responses were seen only in the amygdala, prefrontal cortex, and hypothalamus, but then only at the lower dose. The dopaminergic responses were more complex and not always dose-dependent. The DOPAC/DA ratio was decreased only in the amygdala and striatum at the lower dose, and the olfactory tubercles at the higher dose. It was increased in the septum. The HVA/DA ratios were decreased in the amygdala, prefrontal cortex, and hypothalamus, but only at the lower dose (like MHPG/NE). The 3MT/DA ratio was decreased in the thalamus at the lower dose and in the olfactory tubercles at the higher dose, whereas it was increased in the prefrontal cortex at the lower dose. The HVA and DOPAC routes of degradation were both utilized only by the amygdala. Thus, cocaine produced its most comprehensive effects in this nucleus, as well as the greatest absolute percentage changes for all three of the monoamine systems studied.     

Neurochemical changes in rats chronically treated with a high concentration of manganese chloride

Several neurochemical parameters were studied in brain regions of rats chronically treated with a high concentration of manganese chloride (20 mg MnCl₂.4H₂O per ml. of drinking water) throughout development until adulthood. Large increases in Mn accumulation were found in all brain regions (hypothalamus, +530%; striatum, +479%; other regions, +152 to +250%) of Mn-treated adult rats. In these animals, Ca levels were decreased (–20 to –46%) in cerebellum, hypothalamus, and cerebral cortex but were increased (+186%) in midbrain. Mg levels were decreased (–12 to –32%) in pons and medulla, midbrain, and cerebellum. Fe levels were increased (+95%) in striatum but were decreased (–28%) in cerebral cortex. Cu levels were increased (+43 to +100%) in pons and medulla and striatum but Zn levels were decreased (–30%) in pons and medulla. Na levels were increased (+22%) in striatum but those of K and Cl remained unchanged. Type A monoamine oxidase activities were decreased (–13 to –16%) in midbrain, striatum, and cerebral cortex, but type B monoamine oxidase activities decreased (–13%) only in hypothalamus. Acetylcholinesterase activities were increased (+20 to +22%) in striatum and cerebellum. The results are consistent with out hypothesis that chronic manganese encephalopathy not only affects brain metabolism of Mn but also that of other metals.We dedicate this paper to Professor Alan N. Davison. Professor Davison has conducted pioneering research in several important areas including: brain development and myelination, aging and Alzheimer's disease, and multiple sclerosis. He encouraged us to investigate the neurochemical mechanisms of neurotoxicity of metal ions, particularly in connection with neurological diseases. His encouragement and continued support facilitated the launching of our multidisciplinary research program in the long-term effects of manganese toxicity on brain development and aging.     

Central connections of the olfactory bulb in the bichir,Polypterus palmas,reexamined

Summary Central connections of the olfactory bulb of Polypterus palmas were studied with the use of horseradish peroxidase and cobalt-tracing techniques. The olfactory bulb projects to subpallial and palliai areas in the ipsilateral telencephalon; a projection to the contralateral subpallium is noted via the habenular commissure. A further target of secondary olfactory fibers is a caudal olfactory projection area in the ipsilateral hypothalamus. No labeling was seen in the anterior commissure and in the contralateral olfactory bulb. The medial and the lateral pallium receive secondary olfactory fibers in distinct areas. Neurons projecting to the bulb are found in the ipsilateral subpallium, mainly in one dorsal longitudinal nucleus. The main connection with the tel- and diencephalon is mediated via the medial olfactory tract. This tract also contains fibers to the contralateral telencephalon, and to the hypothalamus. The smaller lateral olfactory tract mediates fibers to the lateral pallium. The organization of pathways of secondary olfactory fibers in the telencephalon is described. The present findings are compared to those obtained in species possessing an inverted forebrain.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft to DLM     

Trypanosoma evansi: Adenosine deaminase activity in the brain of infected rats

The study was undertaken to evaluate changes in the activity of adenosine deaminase (ADA) in brains of rats infected by Trypanosoma evansi. Each rat was intraperitoneally infected with 10⁶ trypomastigotes either suspended in fresh (group A; n = 13) and cryopreserved blood (group B; n = 13). Thirteen animals were used as control (group C). ADA activity was estimated in the cerebellum, cerebral cortex, striatum and hippocampus. No differences (P > 0.05) in ADA activity were observed in the cerebellum between infected and non-infected animals. Significant (P < 0.05) reductions in ADA activity occurred in cerebral cortex in acutely (day 4 post-infection; PI) and chronically (day 20 PI) infected rats. ADA activity was significantly (P < 0.05) decreased in the hippocampus in acutely infected rats, but significantly (P < 0.05) increased in the chronically infected rats. Significant (P < 0.05) reductions in ADA activity occurred in the striatum of chronically infected rats. Parasites could be found in peripheral blood and brain tissue through microscopic examination and PCR assay, respectively, in acutely and chronically infected rats. The reduction of ADA activity in the brain was associated with high levels of parasitemia and anemia in acute infections. Alterations in ADA activity of the brain in T. evansi-infected rats may have implications for pathogenesis of the disease.     

Effects of Ethanol In Vitro and In Vivo on the Release of Endogenous Catecholamines from Specific Regions of Rat Brain

Blocks of tissue from the hypothalamus, olfactory bulb, or striatum of rats were incubated in vitro to study the basal and potassium-stimulated release of endogenous catecholamines. When ethanol (100-250 mM) was added to these preparations in vitro no changes in release were observed. When ethanol (3.0 g X kg-1) was injected intraperitoneally in vivo, however, and 3,4-dihydroxyphenylethylamine (DA, dopamine) release was measured in vitro at various times after drug administration, significant increases in the basal release and decreases in the potassium-stimulated release were observed in striatum and olfactory bulb. In striatum, these changes showed a more rapid onset and a longer duration than in olfactory bulb. In both brain regions, DA release did not differ from controls at 4-6 h after the ethanol injection, although blood ethanol concentrations remained elevated. This may imply the tissue's acquisition of acute functional tolerance to the drug. Similar increases and decreases in the basal and the potassium-induced release of DA from striatal tissues were also found at 1 h after injection of a lower dose of ethanol (1.0 g X kg-1). In terms of behavior, this lower dose of ethanol produced only mild intoxication and ataxia, in contrast to the loss of righting reflex following the higher dose.     

Regional increase of cyclic GMP by atrial natriuretic factor in rat brain: markedly elevated response in spontaneously hypertensive rats

Atrial natriuretic factor (ANF)-responsive areas in rat brain were examined by measuring ANF-stimulated cyclic GMP production in rat brain slice preparations. The medulla oblongata, thalamus, and pituitary gland responded most sensitively, the septum, hypothalamus, pons, midbrain and olfactory bulb responded moderately, but neocortex, cerebellum, striatum and hippocampus were unresponsive to ANF. The most responsive regions in spontaneously hypertensive rats brains showed 2 to 5 times higher cyclic GMP production than those from the control Wistar-Kyoto rats. These findings provide evidence for biological action of ANF on brain tissues, and indicate the action of ANF produced in the brain.