摘要:

AbstractA purified polyclonal antibody preparation was made against recombinant human brain‐derived neurotrophic factor (BDNF) in guinea pig and characterized for use in immunoassays and immunohistochemistry. The anti‐BDNF antibodies specifically recognized BDNF in Western blots and immunoprecipitation. There was no cross‐reactivity with the other known mammalian members of the neurotrophin family, nerve growth factor, neurotrophin‐3 and neurotrophin‐4/5. In immunohistochemical analysis, the anti‐BDNF recognized exogenous BDNF injected into the brain of rats, whereas no signal was obtained with the other neurotrophins. Preabsorption with native BDNF abolished the immunoreactivity in brain sections. These studies identify the anti‐BDNF as a tool for immunocytochemistry and the development of an immunoassay. Immunohistochemical analysis revealed widespread neuronal localization of BDNF in many brain areas. BDNF was localized in all subpopulations of hippocampal neurons. The distribution in the hippocampus suggests localization in the cytoplasm of cell bodies

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00703.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCerebral ischaemia causes activation of ornithine decarboxylase followed by accumulation of putrescine, and these biochemical phenomena have been thought to contribute to the development of neuronal damage. We have used a transgenic mouse line overexpressing the human ornithine decarboxylase gene in their neurons with constitutively high putrescine to study the possible role of putrescine in development of neuronal damage in forebrain ischaemia. An incomplete forebrain ischaemia model was developed in which common carotid arteries were bilaterally occluded and reduction of blood pressure caused by orthostatic reaction was used as a way of decreasing cerebral circulation. Cerebral high‐energy metabolites, intracellular pH and lactate were monitored by means of31P and1H nuclear magnetic resonance spectroscopy respectively. Incomplete ischaemia for 15 min resulted in severe energy failure, as indicated by an increase in the inorganic phosphate/phosphocreatine ratio, intracellular acidification from a pH of ∼7.1 to ∼6.5 and an increase in lactate concentration from<1 to ∼10 mmol/kg in both syngenic and transgenic mice. Following deocclusion, recovery of energy metabolites, intracellular pH and lactate were identical in both animal groups. Ornithine decarboxylase activity rose 9‐ and 3‐fold in syngenic and transgenic mice respectively 6 h after ischaemia. Activation of ornithine decarboxylase resulted in extensive accumulation of putrescine in the brains of transgenic animals 12–24 h after ischaemia, which was ∼50‐fold greater than the basal level in syngenic mice.In situhybridization experiments revealed induction of transcription factors c‐Fos and zif‐268 in the hippocampus, throughout the cerebral cortex and striatum 1–3 h after ischaemia. Messenger RNA of heat shock protein 70 was induced in dentate gyrus and CA3 and CA4 subfields of the hippocampus 1 h after ischaemia. The distribution and extent of induced mRNAs were similar in syngenic and transgenic animals. Histological evaluation did not reveal any difference between the two animal groups despite large variation in their cerebral putrescine content. Neuronal necroses were observed in the CA4 layer of hippocampi in both syngenic and transgenic mice. These data suggest that ornithine decarboxylase activation and accumulation of endogenous putrescine are indicative of an ischaemic insult and that these changes reflect an adaptive response rather than acting as causative fac

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00704.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractProdynorphin mRNA and immunoreactive dynorphin A (ir‐dynorphin A) levels were measured in different brain areas at various time points after amygdala kindled seizures. In the hippocampus, striatum and hypothalamus, prodynorphin mRNA levels were not significantly changed in kindled rats (killed 1 week after the last stimulus‐evoked seizure), but they were significantly increased 1 h after seizures. The relative increase was the highest in the hippocampus (∼3‐fold). In the brainstem, midbrain and cerebral cortex no changes in prodynorphin mRNA were detected in kindled rats, 1 h or 1 week after a kindled seizure. ir‐Dynorphin A levels were significantly reduced in the hippocampus and in the striatum of kindled rats, as well as 5 and 60 min after kindled seizures, but they were increased back to control levels after 120 min. In the hypothalamus, ir‐dynorphin A levels were significantly increased 120 min after a kindled seizure. ir‐Dynorphin A levels were also significantly reduced in the brainstem and in the frontal, parietal and temporal cortex 120 min, but not 5 or 60 min, after a kindled seizure. Taken together, these data support the hypothesis that the dynorphinergic system is activated after amygdala kindled seizures, with different kinetics in differen

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00705.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious experiments using metamizol have shown that this non‐steroidal anti‐inflammatory drug (NSAID) produces a central anti‐nociceptive effect probably through neural substrates that also support the analgesic effects of opiates, such as the periaqueductal grey matter (PAG) and the off‐ and on‐cells of the rostral ventromedial medulla (RVM). Off‐ and on‐cells have been postulated to respectively inhibit and facilitate nociceptive transmission, since the heat‐elicited tail flick reflex (TF) occurs only after off‐cells have decreased (pause), and on‐cells have increased (burst) their activity. The aim of the present study was to examine whether the effect of metamizol upon TF and off‐ and on‐cells responses could be generalized to other NSAIDs such as, in this case, lysine‐acetylsalicylate (LASA). Fifty‐nine off‐ and on‐cells of the RVM were recorded in lightly anaesthetized rats. Systemic administration (200 and 300 mg/kg) or PAG microinjection (30, 50 and 100 μg) of LASA caused retardation of the heat‐elicited off‐cell pause, on‐cell burst and the corresponding TF. Neuronal responses and TF retained their mutual time relationship but shifted simultaneously toward longer latencies. This anti‐nociceptive effect of LASA was dose‐dependent, present 5 min after administration and reached a maximum in 30 min for both administration methods. These data confirm that analgesics typically defined as peripherally‐acting, such as metamizol and LASA in this study, may also have an anti‐nociceptive effect by acting directly upon PAG, and suggest that this cen

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00706.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThree cynomolgus monkeys (Macaca fascicularis) were trained preoperatively in visual discrimination learning for an auditory secondary reinforcer. Each new discrimination problem was solved on the basis of the secondary reinforcer, and primary reinforcement (food reward) was given only after a new problem had been solved. The animals learned 50 new problems in each daily session and it was therefore possible to assess accurately their average rate of learning new discrimination problems in this procedure. After the learning rate had stabilized preoperatively the animals were operated upon to transect the uncinate fascicle, the cortico‐cortical pathway from visual association cortex in the temporal lobe to prefrontal cortex. The animals' learning rate was unchanged after uncinate fascicle section. A previous experiment had shown that visual learning for an auditory secondary reinforcer is unaffected by disconnection of visual association cortex from the amygdala and the fornix. Taken together, this negative evidence points strongly to the conclusion that visual learning for an auditory secondary reinforcer depends upon interaction of temporal lobe visual association cortex with the corpus striatum, since other possibilities have been exclude

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00707.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRecently, we could demonstrate that ‘complex’ glial cells in mouse hippocampal slices express glutamate receptor channels of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA)/kainate subtypes. In the present study, we further characterized this glial receptor. Since voltage‐clamp control is imperfect and diffusion barriers hinder the quantitative analysis of the receptor currentsin situ, the patch‐clamp technique was applied to glial cells acutely isolated from the mouse hippocampal CA1 stratum radiatum subregion. A concentration‐clamp technique was used which enabled very fast exchange of the extracellular solutions. Thus, it was possible to characterize the transient receptor currents with high time resolution. Application of L‐glutamate, AMPA and L‐homocysteate induced rapidly activating and fast desensitizing receptor currents in the suspended glial cells. In contrast, kainate induced non‐desensitizing currents. The corresponding dose‐response curve revealed a half‐maximum of current activation at 350 μM. The current/voltage relationship of the kainate‐evoked response was linear, with a reversal potential at ∼9 mV. Analysis of the reversal potential in solutions containing high concentrations of CaCl2confirmed earlierin situdata by demonstrating significant Ca2+permeability of the glial glutamate receptor channels in the hippocampus. The kainate‐induced receptor currents were markedly increased by cyclothiazide, a substance which selectively potentiates glutamate receptors of the AMPA subtype. We conclude that glial cells of the juvenile hippocampus mainly express heteromeric high‐affinity AMPA receptors. Most probably, the receptor channels are assembled from the low Ca2+‐permeable glutamate receptor‐2 subunit togeth

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00708.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe possibility of regular activation of unitary excitatory synapses on hippocampal CA1 cells by electrical stimulation of Schaffer collaterals was explored in the rat. The amplitude of the excitatory postsynaptic currents (EPSCs) and failures in response to a range of stimulation intensities around the threshold for the smallest detectable EPSC were analysed. After an abrupt appearance of EPSCs in response to increasing stimulation strength, both EPSC amplitude and failure rate could reach a plateau where increasing stimulation intensity did not cause additional responses. This was interpreted as a regular activation of mainly a single axon. Statistical methods showed, however, that only 12 out of ∼50 experiments using threshold stimulation were without significant contamination from additional fibres. In this subset of experiments, upper limits for contamination from other fibres were estimated by using bootstrapping methods. More than 90% of the responses were probably due to faithful activation of a single axon, assuming that the density of axons connecting to one target cell is relatively homogeneous. This result makes the described method suitable for examining some aspects of the transmission between individual hippocampal cell

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00709.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractUsing a corticostriatal slice preparation, we have recently shown that tetanic stimulation of the corticostriatal pathway produces long‐term depression (LTD) of striatal excitatory synaptic transmission. In the present study we have analysed the relationship between LTD and the striatal release of different endogenous transmitters. Samples of perfusate were collected via a small cannula placed just above the surface of the striatal slice close to the recording electrode, and were analysed by HPLC. The high‐frequency stimulation (100 Hz, three trains, 3 s duration, 20 s intervals) used to induce LTD caused a significant but transient increase in the release of both excitatory (aspartate and glutamate) and inhibitory (glycine and GABA) amino acid transmitters. Tetanic stimulation also produced a significant, but transient increase in the release of endogenous dopamine. We conclude that the tetanic stimulation of the corticostriatal pathway is able to induce a large but transient release of excitatory amino acids and of dopamine, whose participation in the induction of striatal LTD has been demonstrated previously. Moreover, the maintenance of this form of synaptic plasticity does not seem to require a sustained change in transmitter rele

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00710.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have established a culture system for microexplants of rat cerebellar cortical tissue in which cells develop morphologically, express type‐A receptors for the inhibitory neurotransmitter γ‐aminobutyric acid (GABA) and form GABAergic synaptic connections. Criteria of cell size and shape allow reliable identification of granule and Purkinje neurons, criteria confirmed by studies of the binding of antibodies to calbindin D28K and GABA. Both granule and Purkinje neurons express GABAAreceptors, but granule neurons fall into two classes in terms of their sensitivity. Granule neurons which do not show spontaneous synaptic currents are relatively insensitive to GABA, while granule neurons with synaptic currents are much more sensitive. The responses of Purkinje neurons to applications of 1 μM GABA are relatively insensitive to Zn2+ions (10 μM), and are potentiated by chlordiazepoxide (100 μM) and La3+ions (100 μM). Responses of innervated granule neurons, on the other hand, are blocked more strongly by Zn2+ions, are less affected by chlordiazepoxide and are equally potentiated by La3+ions. Hence these cultures provide a source of identifiable, functionally innervated cells which express distinct types of GABAAr

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00711.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTrans‐1‐aminocyclopentane‐1,3‐dicarboxylic acid, a mixed agonist of all metabotropic glutamate receptor (mGluR) subtypes, is known to produce either neurotoxic or neuroprotective effects. We have therefore hypothesized that individual mGluR subtypes differentially affect neurodegenerative processes. Selective agonists of subtypes which belong to mGluR class II or III, such as (2s, 1′R,2′R,3′R)‐2‐(2,3‐dicarboxycyclopropyl)‐glycine (DCG‐IV) (specific for subtypes mGluR2 or 3) or L‐2‐amino‐4‐phosphonobutanoate and L‐serine‐O‐phosphate (specific for subtypes mGluR4, 6 or 7), were highly potent and efficacious in protecting cultured cortical neurons against toxicity induced by either a transient exposure toN‐methyl‐D‐aspartate (NMDA) or a prolonged exposure to kainate. In contrast, agonists that preferentially activate class I mGluR subtypes (mGluR1 or 5), such as quisqualate ortrans‐azetidine‐2,3‐dicarboxylic acid, were inactive. DCG‐IV was still neuroprotective when applied to cultures after the toxic pulse with NMDA. This delayed rescue effect was associated with a reduction in the release of endogenous glutamate, a process that contributes to the maturation of neuronal damage. We conclude that agonists of class II or III mGluRs are of potential interest in the experimental ther

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00712.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY