"In vitro" effect of cumene hydroperoxide on hepatic elongation factor-2 and its protection by melatonin

We have examined by immunoblotting the effect of three oxidant compounds on the level of hepatic elongation factor-2 (eEF-2). Rat liver homogenates were exposed to cumene hydroperoxide (CH), 2-2'-azobis (2-aminopropane) dihydrochloride (AAPH) and H(2)O(2). Only CH treatment produced the disappearance of eEF-2, probably due to a phenomena of peptide bond cleavage. The direct implication of free radical species in this process is evident because of the fact that the inclusion of a free radical scavenger such as melatonin prevented the eEF-2 depletion. The results also suggest that the disappearance of eEF-2 induced by CH can be linked to a lipid peroxidant process, which could account for the decline of protein synthesis in aging and other circumstances where lipid peroxidation is high.

Effect of prenatal exposure to ethanol on hepatic elongation factor-2 and proteome in 21 d old rats: protective effect of folic acid

In this article, we study the effects of ethanol intake during pregnancy and lactation on hepatic and pancreatic elongation factor-2 (EF-2) of 21 d old progeny. At the same time, the effect of ethanol on the level of other relevant hepatic proteins was determined using proteomic analysis. The results show that ethanol not only produces a general increase of protein oxidation, but also produces an important depletion of EF-2 and several other proteins. Among the hepatic proteins affected by ethanol, the concomitant supplementation with folic acid to alcoholic mother rats prevented EF-2, RhoGDI-1, ER-60 protease, and gelsolin depletion. This protective effect of folic acid may be related to its antioxidant properties and suggests that this vitamin may be useful in minimizing the effect of ethanol in the uterus and lactation exposure of the progeny.

DCG-IV but not other group-II metabotropic receptor agonists induces microglial BDNF mRNA expression in the rat striatum. Correlation with neuronal injury

We have previously described a neuroprotective action of (2S,2'R,3'R)-2-(2'3'-dicarboxycyclopropyl)glycine (DCG-IV), an agonist for group-II metabotropic receptors, on dopaminergic nerve terminals against the degeneration induced by 1-methyl-4-phenylpyridinium (MPP+). This effect was accompanied by an up-regulation of brain-derived neurotrophic factor (BDNF) mRNA expression in the rat striatum. We have now analyzed the phenotypic nature of the BDNF mRNA-expressing cells in response to intrastriatal injection of DCG-IV. Dual in situ hybridization and immunohistochemistry revealed that microglial cells but not astrocytes were responsible for this induction. Subsequent analysis demonstrated that this effect was accompanied by striking loss of striatal glutamic acid decarboxylase (GAD) mRNA and massive appearance of internucleosomal DNA fragmentation, a hallmark of apoptosis. A dose-response study demonstrated that doses of DCG-IV as low as 5 nmol was very toxic in terms GAD mRNA and apoptosis. 0.5 nmol of DCG-IV did not induce toxicity at all in terms of GAD mRNA and apoptosis. Activation of group-II metabotropic receptors in striatum with N-Acetyl-Asp-Glu (NAAG; a mGlu3 agonist) and (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (a mGlu2 and mGlu3 agonist) did not induce neither loss of GAD mRNA nor appearance of apoptosis (doses up to 20 nmol). In additional experiments, NAAG, in contrast to DCG-IV, failed to protect the striatal dopaminergic system against the degeneration induced by MPP+ as studied by microdialysis. Finally, we studied the mechanism by which DCG-IV is highly toxic. For that, selective antagonists of either metabotropic--(R,S)-alpha-methyl-4-carboxyphenylglycine and LY 341495--or ionotropic (N-methyl-D-aspartate, NMDA)--DL-2-amino-5-phosphonovaleric acid (AP-5) glutamate receptors --were co-administered with DCG-IV. Only AP-5 highly protected the striatum against the degeneration induced by DCG-IV. Since DCG-IV also activates the NMDA receptor at concentrations higher than 3 microM, it is conceivable that a intrastriatal concentration equal or higher than 3 microM after a single striatal injection of 5-20 nmol of DCG-IV. Our findings suggest that much caution must be exerted when testing the numerous neuroprotective effects ascribed to group-II metabotropic receptor activation, in particular when using DCG-IV. We conclude that the neuroprotectant capability of a given compound on a specific system does not exclude the possibility of inducing toxicity on a different one.

Comparative study of the neuroprotective effect of dehydroepiandrosterone and 17beta-estradiol against 1-methyl-4-phenylpyridium toxicity on rat striatum

The effects of dehydroepiandrosterone, estradiol and testosterone on 1-methyl-4-phenylpyridium (MPP+)-induced neurotoxicity of the nigrostriatal dopaminergic system were examined in rat. They were subjected to a unilateral intrastriatal infusion of the following treatment conditions: MPP+ alone or co-injection of MPP+ plus each hormone. Four days after injection, concentrations of dopamine and their metabolites were determined from the corpus striatum. To corroborate the neurochemical data an immunohistochemical analysis of tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase histochemistry in the striatum was performed. Moreover, we performed a dose-response study of the three hormones on the high-affinity dopamine transport system in rat striatal synaptosomes. Rats co-injected within the striatum with MPP+ and either dehydroepiandrosterone or estradiol had significantly greater concentrations of dopamine and less tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase fiber density loss compared with their respective controls. In addition, 4 days after injection, the brain was fixed and cut into coronal sections, and was immunostained with major histocompatibility complex class II antigens for activated microglia, and glial fibrillary acidic protein for activated astrocytes. Dehydroepiandrosterone also attenuated microglial cell activation. In contrast, testosterone showed reductions in dopamine concentrations similar to those obtained by MPP+. The protective effect of dehydroepiandrosterone against the MPP+ neurotoxic dopaminergic system may be produced by its partial prevention of MPP+ inhibition of NADH oxidase activity, whereas the estradiol may function as a neuroprotectant by reducing the uptake of MPP+ into dopaminergic neurons. Our findings we suggest indicate that dehydroepiandrosterone and estradiol by a non-genomic effect may have an important modulatory action, capable of attenuating degeneration within the striatum, and in this way serve as neuroprotectants of the nigrostriatal dopaminergic system.

The degenerative effect of a single intranigral injection of LPS on the dopaminergic system is prevented by dexamethasone, and not mimicked by rh-TNF-alpha, IL-1beta and IFN-gamma

It is becoming widely accepted that the inflammatory response is involved in neurodegenerative disease. In this context, we have developed an animal model of dopaminergic system degeneration by the intranigral injection of lipopolysaccharide (LPS), a potent inductor of inflammation. To address the importance of the inflammatory response in the LPS-induced degeneration of nigral dopaminergic neurones, we carried out two different kinds of studies: (i) the possible protective effect of an anti-inflammatory compound, and (ii) the effect of the intranigral injection of inflammatory cytokines (TNF-alpha, IL-1beta and IFN-gamma) on dopaminergic neurones viability. Present results show that dexamethasone, a potent anti-inflammatory drug that interferes with many of the features characterizing pro-inflammatory glial activation, prevented the loss of catecholamine content, Tyrosine hydroxylase (TH) activity and TH immunostaining induced by LPS-injection and also the bulk activation of microglia/macrophages. Surprisingly, injection of the pro-inflammatory cytokines failed to reproduce the LPS effect. Taken together, our results suggest that inflammatory response is implicated in LPS-induced neurodegeneration. This damage may be due, at least in part, to a cascade of events independent of that described for TNF-alpha/IL-1 beta/IFN-gamma.

[Can sural nerve biopsy be used to orientate the treatment of chronic inflammatory demyelinating polyneuropathy?]

INTRODUCTION

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired neuropathy characterized by demyelination of the peripheral nerves and roots. The course of the illness is progressively chronic or of relapses and remissions. Biopsy of the sural nerve is not essential for diagnosis. It is therefore not necessary to carry it out on all occasions, but probably permits a more rational approach to treatment.

OBJECTIVE

To show whether biopsy of the sural nerve is useful for orientation of the treatment required in cases of CIDP.

PATIENTS AND METHODS

We studied a total of 16 patients admitted to hospital with a diagnosis of CIDP. They had neurophysiological studies, sural nerve biopsy and other studies to rule out other diagnoses. The patients were assigned to the therapeutic protocols recommended. During 8 years of follow up we compared the response to treatment with intacglobin/plamapheresis, steroids and cytostatic drugs.

RESULTS

It was highly significant (p< 0.001) that the patients with axon lesions on sural nerve biopsy did not respond to treatment with intac globin/plasmapheresis or steroids but did respond to cyclophosphamide, without any serious adverse effects being seen.

CONCLUSIONS

Axonal histopathological lesions of CIDP at the onset of the disease may require cytostatic treatment since they do not usually improve on standard treatment. Sural biopsy is usually invaluable in such cases.

Potential role of endogenous brain-derived neurotrophic factor in long-term neuronal reorganization of the superior colliculus after bilateral visual deprivation

The role of the brain-derived neurotrophic factor (BDNF), the BDNF receptor (TrkB), and the glutamic acid decarboxylase (GAD67) after neonatal, bilateral nerve deafferentiation during postnatal development was investigated in the rat superior colliculus (SC). BDNF and GAD67 mRNA expression were significantly increased in optic (Op) and intermediate gray (InG) layers at 5, 8, 15, and 21 days after birth, but not in adult animals. However, TrkB mRNA expression was not modified at any time tested. At 15 days, where changes in BDNF and GAD67 mRNAs were more evident, an upregulation of the NMDAR(1A) mRNA glutamate receptor in the Op and InG, a modification in the pattern of synaptic zinc in the superficial layers of SC, and an increased synaptophysin immunoreactivity in the Op was found. This indicates the existence of a synergic mechanism between BDNF and NMDA to determine refinement of connections after the loss of visual input in SC.

Validity of a quantitative technique to study striatal dopaminergic neurodegeneration by in vivo microdialysis

The development of a technique that allows the direct quantitative study of the damage produced by a toxin on a specific neurotransmitter system is very important. For that, we have used the microdialysis technique to validate a method to study the specific drug's toxicity on dopaminergic (DAergic) striatal terminals. We perfused different MPP(+) and 6-hydroxydopamine (6-OHDA) concentrations, with different toxicity for DAergic terminals, 24 h after the implantation of the microdialysis probe (day 1). One day later (day 2), MPP(+) was perfused through the microdialysis probe and DA extracellular output measured. We hypothesize that the amount of extracellular dopamine (DA) obtained on day 2 is directly proportional to the neurotoxic damage produced on day 1. To corroborate this hypothesis tyrosine hydroxylase (TH) immunohistochemistry was also carried out on day 2. There was a clear correlation index between the amount of DA measured after MPP(+) perfusion and the lack of TH immunoreactivity measured as the radius of the area showing decrease in TH immunoreactivity around the cannula. These results show the possibility to measure DAergic remaining terminals after a toxic drug exposure by in vivo MPP(+) perfusion. The possibility to extend this neurotoxic study to another neurotransmitter systems is suggested.

Long-lasting induction of brain-derived neurotrophic factor is restricted to resistant cell populations in an animal model of status epilepticus

We have recently characterized an animal model of status epilepticus induced by a single intraseptal injection of kainate. Under these conditions, there is a delayed expanding apoptotic hippocampal and amygdalar cell death. In order to further characterize this animal model, we have performed a detailed time-course analysis of the appearance of cell death, brain-derived neurotrophic factor messenger RNA expression and astroglial and microglial response in different brain areas related to the limbic system. We found a long-lasting delayed apoptotic cell death in the hippocampal formation, amygdala, medial thalamus, dorsal endopiriform nucleus and multiple cortical areas from two to 21 days post-injection. There was a spatiotemporal correlation between the appearance of cell death and induction of brain-derived neurotrophic factor messenger RNA expression in the areas studied, and interestingly this induction was found in non-degenerating cells. We conclude that our animal model of status epilepticus exhibits remarkable features of recurrent seizure activity and provides evidence for a neuroprotective role of brain-derived neurotrophic factor against seizure-induced apoptotic cell death.

Appropriateness of emergency department visits in a Portuguese university hospital

STUDY OBJECTIVE

There are no studies in Portugal supporting a common claim that most emergency department visits are inappropriate. The aim of this study was to determine the prevalence of and to evaluate factors associated with an appropriate ED visit in a major public hospital.

METHODS

A cross-sectional prospective study was performed at a public university hospital ED. Data for demographic variables, duration of complaint, transfer from other medical sources, and previous medical care for the same complaints were collected by interviewing all patients who arrived at the ED within a consecutive period of at least 24 hours. Data for diagnostic tests, treatment performed, and final patient destination were collected by triage records review. An appropriate ED visit was defined by explicit criteria: interhospital transfer, patient death at the ED, hospitalization, and diagnostic tests or treatments performed.

RESULTS

The study included 5,818 adult patients. The prevalence of an appropriate ED visit, by use of our criteria, was 68.7%. Sex was an effect modifier. According to this study, determinants of an appropriate visit for men and women were age 60 years or older and complaints of 24 hours or less and in women but not in men, retired from work and with arrival between midnight and 8 AM.

CONCLUSIONS

In a university hospital in Oporto, the majority of ED visits were appropriate according to explicit criteria. Some variables may be associated with appropriateness of ED visits. A duration of the complaint 24 hours or less along with an arrival between midnight and 8 AM in women and age 60 years or older in men were the most important determinants.

Decreased messenger RNA expression of key markers of the nigrostriatal dopaminergic system following vitamin E deficiency in the rat

We have evaluated the effect of a vitamin E-deficient diet on the rat nigrostriatal dopaminergic system. After 15 days of deficient diet, the amount and activity of striatal and nigral tyrosine hydroxylase increased, which contrasted with a decreased messenger RNA expression for tyrosine hydroxylase and the dopamine transporter in the ventral mesencephalon. When we prolonged the deficiency of vitamin E for 30 days, dopamine levels did not differ in both areas. In contrast, messenger RNA levels for tyrosine hydroxylase and the dopamine transporter were markedly reduced in 30-day deficient rats. In addition, the number of oxidatively modified proteins significantly increased in the striatal and nigral areas studied. Overall, we propose that these changes suggest an important role of vitamin E in maintaining the normal equilibrium of the dopaminergic nigrostriatal system.

Enterococcus faecalis resistant to vancomycin and teicoplanin (VanA phenotype) isolated from a bone marrow transplanted patient in Brazil

We report for the first time in Brazil, a patient from whom an Enterococcus faecalis VanA phenotype was isolated. Glycopeptide resistance is not commonly observed in Enterococcus faecalis, so this finding is of great concern since this species is responsible for 90% of enterococcal infections in Brazil. The isolate was recovered from a surveillance rectal swab culture from a patient with acute lymphocytic leukemia (ALL). Identification to the species level was performed by conventional biochemical tests and Vitek GPI cards. Antimicrobial susceptibility testing was evaluated by use of broth microdilution and Etest (AB BIODISK, Solna, Sweden) methods. The isolate was identified as E. faecalis and was considered resistant to both vancomycin (MIC, > 256 microg/mL) and teicoplanin (MIC, 256 microg/mL). The isolate also showed high level resistance to gentamicin and streptomycin (MICs, > 1024 microg/mL), but was considered susceptible to ampicillin (MIC, 4 microg/mL). Although the frequency of enterococcal infections is very low in most Latin America countries, the finding of glycopeptide (VanA) resistance in E. faecalis increases concern about apreading antimicrobial resistance in this region.

Aquaporins in the central nervous system

In this review, we have tried to summarize most available data dealing with the aquaporin (AQP) family of water channels in the CNS. Two aquaporins have been identified so far in the CNS, AQP1 and AQP4. AQP1 is restricted to the choroid plexus of the lateral ventricles, which raises a role for this aquaporin in cerebrospinal fluid formation. AQP4 is the predominant water channel in the brain and it is more widely distributed than originally believed, with a marked prevalence over periventricular areas. In the first part of this review, we examine the complete distribution pattern of AQP4 in the CNS including its rostro-caudal localization to end with its subcellular location. After discussing scarce data dealing with regulation of aquaporins in the CNS, we focus in potential roles for aquaporins. Novel recent data highlights very important roles for this aquaporin in the normal and pathological brain including, among others, role in potassium buffering, body fluid homeostasis, central osmoreception and development and restoration of brain edema.

Group II metabotropic glutamate receptor activation protects striatal dopaminergic nerve terminals against MPP+-induced neurotoxicity along with brain-derived neurotrophic factor induction

We have studied the in vivo effect of the selective agonist for group II metabotropic glutamate receptors (2S, 2'R, 3'R)-2-(2'3'-dicarboxycyclopropyl)glycine (DCG-IV) against MPP+-induced toxicity on rat striatal dopaminergic nerve terminals by using both microdialysis and immunohistochemical techniques. Perfusion of 1 mM DCG-IV during 1 h protected dopaminergic nerve terminals against the degeneration induced by a 15-minute perfusion of 1 mM MPP+. In addition, the microglial cell population was markedly activated 24 h after DCG-IV perfusion. The astroglial cell population was only markedly activated around the microdialysis probe. This protective effect seems to be dependent on protein synthesis since 1 mM cycloheximide, an inhibitor of protein synthesis, abolished the neuroprotective effect of 1 mM DCG-IV against MPP+ toxicity. Perfusion of DCG-IV induced an upregulation of striatal brain-derived neurotrophic factor (BDNF) mRNA expressing cells which were confined precisely around the microdialysis probe. Taken together, our results suggest that the induction and release of brain-derived neurotrophic factor (BDNF) by activated glial cells induced by DCG-IV perfusion may account for its protective action against MPP+-induced dopaminergic terminal degeneration.

Low selenium diet induces tyrosine hydroxylase enzyme in nigrostriatal system of the rat

We have studied the effect of a selenium-deficient diet on the nigrostriatal dopaminergic system for 15 and 30 days. The neurochemical analysis demonstrated significant elevations in nigral DA levels after 15 and 30 days of selenium deficiency. The most significant change in striatum was an elevation in dopamine (DA) in 30-day-deficient animals. As a further step, we measured the levels of activity and mRNA expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT). There were significant elevations in all of these parameters in the nigrostriatal system following selenium deficiency at the two time-points studied except for the striatal DA uptake at day 30, which dropped to control levels. Altogether, our results suggest that the decrease in antioxidant capacity due to a selenium deficiency promotes an increase in DA synthesis and turnover, which are clearly associated to the induction of TH. This effect may trigger a positive feed-forward mechanism that could increase the oxidative stress considering the capacity of DA to generate free radicals.

Protective effect of melatonin against the 1-methyl-4-phenylpyridinium-induced inhibition of complex I of the mitochondrial respiratory chain

In the present study, a novel property of melatonin is shown: a protective effect of melatonin on the respiratory chain in isolated rat liver mitochondria and in striatal synaptosomes treated with 1-methyl-4-phenylpyridinium ion (MPP+). The cellular damage caused by MPP+, a compound that produces a Parkinsonian-like syndrome in humans, is the result of the mitochondrial respiration inhibition at the Complex I level and oxidative stress induction. Treatment of mitochondria with MPP+ inhibits the respiration rate. This effect was prevented by the inclusion of melatonin in the incubation mixture. This preventive effect, which is not related to the antioxidative properties of melatonin, seems to be due to the fact that melatonin prevents MPP+ interaction with Complex I. These results suggest that melatonin may protect against the effect of several Parkinsonogenic compounds that are associated with progressive impairment of mitochondrial function and increased oxidative damage.

The single intranigral injection of LPS as a new model for studying the selective effects of inflammatory reactions on dopaminergic system

We have injected lipopolysaccharide (LPS) into the nigrostriatal pathway of rats in order to address the role of inflammation in Parkinson's disease (PD). LPS induced a strong macrophage/microglial reaction in Substantia nigra (SN), with a characteristic clustering of macrophage cells around blood-vessels. The SN was far more sensitive than the striatum to the inflammatory stimulus. Moreover, only the dopaminergic neurons of the SN were affected, with no detectable damage to either the GABAergic or the serotoninergic neurons. The damage to the DA neurons in the SN was permanent, as observed 1 year postinjection. Unlike the direct death of dopaminergic neurons caused by agents as MPP(+) or 6-OHDA, LPS seems to cause indirect death due to inflammatory reaction. Therefore, we suggest that the injection of a single dose of LPS within the SN is an interesting model for studying the selective effects of inflammatory reaction on dopaminergic system and also potentially useful for studying PD.

Histamine infusion induces a selective dopaminergic neuronal death along with an inflammatory reaction in rat substantia nigra

We have evaluated the effects of a direct infusion of histamine, as mediator of inflammatory response, in substantia nigra, striatum, medial septum, and medial lemniscus. Injection of 100 and 250 nmol of histamine in substantia nigra produced a selective damage in dopaminergic neurons evidenced by the loss of tyrosine hydroxylase mRNA-expressing cells, tyrosine hydroxylase-immunolabeled-positive cell bodies, and dopamine and 3,4-dihydroxyphenylacetic acid levels. In parallel we found an acute inflammatory response manifested by a loss of glial fibrillary acidic protein-immunolabeled astrocytes and, at precisely the same area, an activation of microglia. In the striatum, only high doses (500 nmol) produced an evident terminal degeneration. The selective neurotoxicity of histamine for dopaminergic cells was demonstrated by the unaltered transcription of glutamic acid decarboxylase mRNA in substantia nigra. Moreover, intraseptal injection of 100 nmol of histamine failed to alter the pattern of choline acetyltransferase mRNA-expressing cells, and intraparenchymal injection of histamine in medial lemniscus failed to alter the pattern of serotonin-immunolabeled cells. We conclude that the substantia nigra is highly sensitive to histamine-derived neurotoxicity, where inflammatory processes mediated by histamine could be important in the pathological changes that lead to dopaminergic neuronal damage after histamine infusion.

Shifts in the psychometric function and their implications for models of timing

This study examined how two models of timing, scalar expectancy theory (SET) and learning to time (LeT), conceptualize the learning process in temporal tasks, and then reports two experiments to test these conceptualizations. Pigeons responded on a two-alternative free-operant psychophysical procedure in which responses on the left key were reinforceable during the first two, but not the last two, quarters of a 60-s trial, and responses on the right key were reinforceable during the last two, but not the first two, quarters of the trial. In Experiment 1 three groups of birds experienced a difference in reinforcement rates between the two keys only at the end segments of the trial (i.e., between the first and fourth quarters), only around the middle segments of the trial (i.e., between the second and third quarters), or in both end and middle segments. In Condition 1 the difference in reinforcement rate favored the left key; in Condition 2 it favored the right key. When the reinforcement rates differed in the end segments of the trial, the psychometric function--the proportion of right responses across the trial--did not shift across conditions; when it occurred around the middle of the trial or in both end and middle segments, the psychometric function shifted across conditions. Experiment 2 showed that the psychometric function shifts even when the overall reinforcement rate for the two keys is equal, provided the rates differ around the middle of the trial. This pattern of shifts of the psychometric function is inconsistent with SET. In contrast, LeT provided a good quantitative fit to the data.

The endogenous amine 1-methyl-1,2,3,4- tetrahydroisoquinoline prevents the inhibition of complex I of the respiratory chain produced by MPP(+)

The endogenous monoamine 1-methyl-1,2,3,4-tetrahydroisoquinoline has been shown to prevent the neurotoxic effect of MPP(+) and other endogenous neurotoxins, which produce a parkinsonian-like syndrome in humans. We have tested its potential protective effect in vivo by measuring the protection of 1-methyl-1,2,3,4-tetrahydroisoquinoline in the neurotoxicity elicited by MPP(+) in rat striatum by tyrosine hydroxylase immunocytochemistry. Because we know that cellular damage caused by MPP(+) is primarily the result of mitochondrial respiratory inhibition at the complex I level, we have extended the study further to understand this protective mechanism. We found that the inhibitory effect on the mitochondrial respiration rate induced by MPP(+) in isolated rat liver mitochondria and striatal synaptosomes was prevented by addition of 1-methyl-1,2,3,4-tetrahydroisoquinoline. This compound has no antioxidant capacity; therefore, this property is not involved in its protective effect. Thus, we postulate that the preventive effect that 1-methyl-1,2,3,4-tetrahydroisoquinoline has on mitochondrial inhibition for MPP(+) could be due to a "shielding effect," protecting the energetic machinery, thus preventing energetic failure. These results suggest that this endogenous amine may protect against the effect of several parkinsonism-inducing compounds that are associated with progressive impairment of the mitochondrial function.

Neurotoxic relationship between dopamine and iron in the striatal dopaminergic nerve terminals

The neurotoxic effect of dopamine (DA) and iron(III) on DAergic terminals in striatum has been studied by intracerebral microdialysis technique. Twenty-four hours after surgery (day 1), DA and/or iron(III) with and without DA reuptake inhibitor, nomifensine, were perfused for 1 h. Forty-eight hours after surgery (day 2), MPP(+) 1 mM was perfused for 15 min and the output of DA was measured, its amount being directly proportional to the remaining striatal DAergic terminals, supported by tyrosine hydroxylase immunohistochemistry technique. Perfusion of exogenous DA, as well as iron(III) 10 and 100 microM, did not produce any neurotoxic effect. However, perfusion of iron(III) (333 and 1000 microM) produced a concentration-dependent toxic effect. Co-perfusion of iron(III) at non-toxic concentration (100 microM) with DA (15 microM) produced a toxic effect. Elevation of the endogenous extracellular levels of DA by inhibiting its uptake with nomifensine increased the neurotoxic effect of iron(III) in a dose-dependent manner. The use of tetrodotoxin after elevation of DA with nomifensine partially prevented the neurotoxic effect of its co-perfusion with iron(III) (100 microM). These results suggest that DAergic system could be synergistically damaged by DA and iron(III). Thus, alterations in the clearance of DA from extracellular space along with an increase of iron may have significant consequences for DAergic system toxicity.

Delayed apoptotic pyramidal cell death in CA4 and CA1 hippocampal subfields after a single intraseptal injection of kainate

We have performed a detailed time-course analysis of cell death in the hippocampal formation, basal forebrain and amygdala following a single intraseptal injection of kainate in adult rats. Acetylcholinesterase histochemistry revealed a profound loss of staining in the medial septum but not in the diagonal band, and cholinergic fiber density was highly reduced in the hippocampus and amygdala at 10 days postinjection. Terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphatebiotin nick end labeling (TUNEL) histochemistry was performed for precise location of apoptotic cells. Both the medial septum and amygdala exhibited numerous TUNEL-positive nuclei after the intraseptal injection of kainate, while the lateral septum exhibited a lower but significant incidence in terms of apoptotic cells. In the medial septum, the presence of apoptotic cells was at a location displaying acetylcholinesterase staining. TUNEL histochemistry revealed a time-dependent sequential apoptotic cell death in hippocampal pyramidal cells. During the first two days postinjection, apoptosis in the hippocampus was only evident in the CA3 region. At five days postinjection, the entire CA4 region became apoptotic. At 10 days postinjection, the whole extent of the CA1 pyramidal cell layer exhibited numerous TUNEL-positive nuclei. The time-course of kainate-induced apoptosis in Ammons's horn correlated with the disappearance of hippocampal pyramidal neurons as detected by Nissl staining, which is suggestive of a prominent apoptotic death for these cells. The temporal delayed distant damage to CA4 and CA1 hippocampal subfields after a single intraseptal kainate injection is not seen in other models employing kainate and may be a valuable tool for exploring the cellular mechanisms leading to cell death in conditions of status epilepticus.