bluuebunny/crossref_metadata_2025 huggingface dataset:
IAP family proteins delay motoneuron cell death in vivo
Authors: Perrelet D. , Ferri A. , MacKenzie A. E. , Smith G. M. , Korneluk R. G. , Liston P. , Sagot Y. , Terrado J. , Monnier D. , Kato A. C.
Published: March 2003

Neuronal apoptosis inhibitory protein (NAIP), and human inhibitors of apoptosis 1 and 2 (HIAP1 and HIAP2) are three members of the mammalian family of antiapoptosis proteins called ‘inhibitors of apoptosis’ (IAP). These molecules can prevent apoptosis in vitro and the over‐expression of NAIP can decrease ischemic damage in the hippocampus. The goal of our experiments was to determine whether administration of NAIP, HIAP1 and HAIP2 could rescue motoneurons following axotomy of a peripheral nerve. In young rats, an adenoviral gene transfer technique was used to deliver and express these proteins in motoneurons; a fluorescent tracer was simultaneously added as a means for quantitatively assessing the rescue of fluorescently labelled motoneurons in serial sections of the lumbar spinal cord. Control experiments using adenoviral vectors (adv) expressing the lacZ gene showed that 14% of the sciatic motoneuron pool could be transfected indicating the existence of a subpopulation of spinal motoneurons susceptible to this class of viral vectors. The administration of an adv‐NAIP, adv‐HIAP1 and adv‐HIAP2 rescued 30–40% of motoneurons at one week after sciatic axotomy. The efficiency of these proteins was similar to that of two neurotrophic factors, ciliary neurotrophic factor and brain‐derived neurotrophic factor, administrated by the same viral technique. The effect of the IAP proteins on motoneuron survival decreased with time but was still present after 4 weeks postaxotomy; the duration of the response was dependent upon the viral titre. These experiments demonstrate that IAP family proteins can prevent motoneuron cell death in vivo and may offer a new therapeutic approach for motoneuron diseases.
Effects of glutamate agonist versus procaine microinjections into the basal forebrain cholinergic cell area upon gamma and theta EEG activity and sleep–wake state
Authors: Cape Edmund G. , Jones Barbara E.
Published: March 2003

Serving as the ventral, extra‐thalamic relay from the brainstem reticular activating system to the cerebral cortex, basal forebrain neurons, including importantly the cholinergic cells therein, are believed to play a significant role in eliciting and maintaining cortical activation during the states of waking and paradoxical sleep. The present study was undertaken in rats to examine the effects upon electroencephalogram (EEG) activity and sleep–wake state of inactivating basal forebrain neurons with microinjections of procaine versus activating them with microinjections of agonists of glutamate, which is the primary neurotransmitter of the brainstem reticular activating system. Microinjections into the basal forebrain were performed using a remotely controlled device in freely moving, naturally sleeping/waking rats during the day when they are asleep the majority of the time. Procaine produced a decrease in gamma (30–60 Hz) and theta (4–8 Hz) EEG activities, and an increase in delta (1–4 Hz) associated with a loss of paradoxical sleep, despite the persistence of slow wave sleep. α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and N‐methyl‐d‐aspartate (NMDA) produced an increase in gamma and a decrease in delta, while eliciting waking. In addition, NMDA, which has been shown in vitro to induce rhythmic bursting in the cholinergic cells, significantly increased theta activity. Following the microinjections of NMDA, c‐Fos protein, which has been shown to reflect neural activity, was found in numerous cholinergic, and also GABAergic (γ‐aminobutyric acid) and other non‐cholinergic neurons, in the substantia innominata and magnocellular preoptic nucleus near the microinjection cannulae. These results substantiate the role of cholinergic, possibly together with other, basal forebrain neurons in cortical activation, including elicitation of gamma and theta activities that underlie cortical arousal during waking and paradoxical sleep.
Electrophysiological properties of microglial cells in normal and pathologic rat brain slices
Authors: Boucsein Clemens , Kettenmann Helmut , Nolte Christiane
Published: March 2003

Microglial cells serve as pathologic sensors of the brain. They are highly abundant in all regions of the central nervous system (CNS) and are characterized by a ramified morphology within the normal tissue. In the present study, we have developed a procedure to study the membrane properties of identified, in situ microglia in acutely isolated brain slices from rat cortex, striatum and facial nucleus. Unlike the well characterized cultured microglial cells, ramified microglia of the slice are characterized by little, if any, voltage‐gated membrane currents and a very low membrane potential. They are thus distinct from neurons, other glial cells and nonbrain macrophages. To study the consequences of microglial activation on the membrane channel pattern, we compared cells in the normal facial nucleus and at defined times after facial nerve axotomy. Within 12 h of axotomy, microglial cells expressed a prominent inward rectifier current and thus acquired the physiological properties of cultured microglia. Within 24 h of the lesion, the cells expressed an additional outward current, which is typical for lipopolysaccharide (LPS)‐activated microglia in vitro. Seven days after the lesion, at a time of major regenerative processes in the facial nucleus, the physiological properties of microglial cells had reverted to those present prior to the pathological event. In conclusion: (i) ramified microglial cells represent a physiologically unique population of cells in the brain; (ii) are distinct from their cultured counterparts; and (iii), undergo a defined pattern of physiological states in the course of pathologic events.
Activation of spinal cannabinoid 1 receptors inhibits C‐fibre driven hyperexcitable neuronal responses and increases [35S]GTPγS binding in the dorsal horn of the spinal cord of noninflamed and inflamed rats
Authors: Drew L. J. , Harris J. , Millns P. J. , Kendall D. A. , Chapman V.
Published: March 2003

The analgesic potential of cannabinoid (CB) receptor agonists is of clinical interest. Improved understanding of the mechanisms of action of cannabinoids at sites involved in the modulation of acute and sustained inflammatory nociceptive transmission, such as the spinal cord, is essential. In vivo electrophysiology was used to compare the effect of the synthetic CB agonist, HU210, on acute transcutaneous electrical‐evoked responses of dorsal horn neurons of noninflamed anaesthetized rats and anaesthetized rats with a peripheral carrageenin inflammation. CB receptor G‐protein coupling in lumbar spinal cord sections of noninflamed and carrageenin‐inflamed rats was studied with in vitro autoradiography of guanylyl 5′‐[γ‐[35S]thio]triphosphate ([35S]GTPγS) binding. Spinal HU210 significantly inhibited the C‐fibre‐mediated late (300–800 ms) postdischarge response of dorsal horn neurons of noninflamed and carrageenin‐inflamed rats; the CB1 receptor antagonist SR141716A blocked the effect of HU210. HU210 had limited effects on A‐fibre‐evoked dorsal horn neuronal responses of both groups of rats. HU210 significantly increased [35S]GTPγS binding in the dorsal horn of the spinal cord of both groups of rats compared with basal [35S]GTPγS binding; SR141716A blocked these effects. The predominant effect of spinal HU210, via CB1 receptor activation, was on the C‐fibre driven postdischarge responses, a measure of neuronal hyperexcitability following repetitive C‐fibre stimulation. Sustained, but not enhanced, antinociceptive effects of HU210 following carrageenin inflammation are reported; CB receptor G‐protein coupling was not altered by inflammation. These results strengthen the body of evidence suggesting CB agonists may be an important novel analgesic approach for the treatment of sustained pain states.
Temporal integration vs. parallel processing: coping with the variability of neuronal messages in directional hearing of insects
Authors: Ronacher Bernhard , Krahe Rüdiger
Published: March 2003

The behaviour of many animals indicates a high precision in the processing of sensory signals, which often seems at odds with the large variability of individual neuronal responses. Using the directional hearing of the grasshopper Chorthippus biguttulus (Ch. biguttulus) as a model system, we investigated the possible contributions of temporal integration and parallel processing at the receptor level to the observed behavioural acuity. The precision of the animals' phonotactic orientation behaviour to stimuli of different durations was measured and compared with the spiking responses of auditory receptor cells, leading to the following results. A behavioural decision based on integrating the spikes from a pair of receptors (one cell in each ear) over a 1000‐ms time window would substantially decrease the error probability, compared with evaluating a 250‐ms period. The animal as a whole, however, responded as precisely to a 250 ms stimulus as to a stimulus of natural duration (c. 1000 ms). A phonotactic decision based on a 1.5 dB intensity difference between the ears corresponds to a spike count difference of approximately 1 spike per 100 ms in a pair of receptors. As these differences are in the order of the statistical spike count fluctuations, the error probabilities for an ideal observer of the spike count are substantially higher (13–18%) than the errors observed in the behavioural tests (only 5%). We conclude that the animals' nervous system has to sample information from a pool of 6–13 receptors to arrive at the observed behavioural precision.
Effects of barium on stimulus‐induced rises of [K+]o in human epileptic non‐sclerotic and sclerotic hippocampal area CA1
Authors: Kivi A. , Lehmann T. ‐N. , Kovács R. , Eilers A. , Jauch R. , Meencke H. J. , Von Deimling A. , Heinemann U. , Gabriel S.
Published: March 2003

In the hippocampus of patients with therapy‐refractory temporal lobe epilepsy, glial cells of area CA1 might be less able to take up potassium ions via barium‐sensitive inwardly rectifying and voltage‐independent potassium channels. Using ion‐selective microelectrodes we investigated the effects of barium on rises in [K+]o induced by repetitive alvear stimulation in slices from surgically removed hippocampi with and without Ammon's horn sclerosis (AHS and non‐AHS). In non‐AHS tissue, barium augmented rises in [K+]o by 147% and prolonged the half time of recovery by 90%. The barium effect was reversible, concentration dependent, and persisted in the presence of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA), N‐methyl‐d‐aspartate (NMDA) and γ‐aminobutyric acid [GABA(A)] receptor antagonists. In AHS tissue, barium caused a decrease in the baseline level of [K+]o. In contrast to non‐AHS slices, in AHS slices with intact synaptic transmission, barium had no effect on the stimulus‐induced rises of [K+]o, and the half time of recovery from the rise was less prolonged (by 57%). Under conditions of blocked synaptic transmission, barium augmented stimulus‐induced rises in [K+]o, but only by 40%. In both tissues, barium significantly reduced negative slow‐field potentials following repetitive stimulation but did not alter the mean population spike amplitude. The findings suggest a significant contribution of glial barium‐sensitive K+‐channels to K+‐buffering in non‐AHS tissue and an impairment of glial barium‐sensitive K+‐uptake in AHS tissue.
Astrocytes in the hippocampus of patients with temporal lobe epilepsy display changes in potassium conductances
Authors: Hinterkeuser Stefan , Schröder Wolfgang , Hager Gerhard , Seifert Gerald , Blümcke Ingmar , Elger Christian E , Schramm Johannes , Steinhäuser Christian
Published: March 2003

Functional properties of astrocytes were investigated with the patch‐clamp technique in acute hippocampal brain slices obtained from surgical specimens of patients suffering from pharmaco‐resistant temporal lobe epilepsy (TLE). In patients with significant neuronal cell loss, i.e. Ammon's horn sclerosis, the glial current patterns resembled properties characteristic of immature astrocytes in the murine or rat hippocampus. Depolarizing voltage steps activated delayed rectifier and transient K+ currents as well as tetrodotoxin‐sensitive Na+ currents in all astrocytes analysed in the sclerotic human tissue. Hyperpolarizing voltages elicited inward rectifier currents that inactivated at membrane potentials negative to ‐130 mV. Comparative recordings were performed in astrocytes from patients with lesion‐associated TLE that lacked significant histopathological hippocampal alterations. These cells displayed stronger inward rectification. To obtain a quantitative measure, current densities were calculated and the ratio of inward to outward K+ conductances was determined. Both values were significantly smaller in astrocytes from the sclerotic group compared with lesion‐associated TLE.

During normal development of rodent brain, astroglial inward rectification gradually increases. It thus appears reasonable to suggest that astrocytes in human sclerotic tissue return to an immature current pattern. Reduced astroglial inward rectification in conjunction with seizure‐induced shrinkage of the extracellular space may lead to impaired spatial K+ buffering. This will result in stronger and prolonged depolarization of glial cells and neurons in response to activity‐dependent K+ release, and may thus contribute to seizure generation in this particular condition of human TLE.
Q‐ and L‐type calcium channels control the development of calbindin phenotype in hippocampal pyramidal neurons in vitro
Authors: Boukhaddaoui Hassan , Sieso Victor , Scamps Frédérique , Vigues Stephan , Roig Anne , Valmier Jean
Published: March 2003

Cultured immature hippocampal neurons from embryonic 17‐day‐old rats were used to explore activity‐dependent regulation of neuronal phenotype differentiation in the developing hippocampus. The calbindin‐D28k phenotype of the pyramidal neurons appeared during the first 6 days in culture, and was expressed by 12% of the cells on day 6. Daily stimulation with 50 mm KCl during the first 5 days in vitro increased the number of calbindin‐D28k‐positive pyramidal neurons without affecting neuronal survival. This effect was prevented by buffering extracellular Ca2+. Omega‐agatoxin‐IVA‐sensitive Q‐type and nitrendipine‐sensitive L‐type voltage‐gated Ca2+ channels (VGCCs) carried Ca2+ currents and Ca2+ influx in immature pyramidal neurons at somata level. Blockade of these channels inhibited calbindin‐D28k phenotype induced by 50 mm KCl. Conversely, glutamate‐activated Ca2+ channel antagonists did not affect the KCl‐induced calbindin‐D28k phenotype. Chronic blockade of Q‐ and/or L‐type VGCCs downregulated the normal calbindin‐D28k development of immature pyramidal neurons without affecting neuronal survival, the somatic area of pyramidal neurons or the number of GABAergic‐positive (γ‐aminobutyric acid) interneurons. However, at later developmental stages, Q‐type VGCCs lost their ability to control Ca2+ influx at somata level, and both Q‐ and L‐type VGCCs failed to regulate calbindin‐D28k phenotype. These results suggest that Q‐type channels, which have been predominantly associated with neurotransmitter release in adult brain, transiently act in synergy with L‐type VGCCs to direct early neuronal differentiation of hippocampal pyramidal neurons before the establishment of their synaptic circuits.
Gephyrin, a major postsynaptic protein of GABAergic synapses
Authors: Sassoè‐Pognetto Marco , Fritschy Jean‐Marc
Published: March 2003

γ‐aminobutyric acid type A (GABAA) receptors are located at the majority of inhibitory synapses in the mammalian brain. However, the mechanisms by which GABAA receptor subunits are targeted to, and clustered in, the postsynaptic membrane are poorly understood. Recent studies have demonstrated that gephyrin, a protein first identified as a component of the glycine receptor (GlyR) complex, is colocalized with several subtypes of GABAA receptors and is involved in the stabilization of postsynaptic GABAA receptor clusters. Thus, gephyrin functions as a clustering protein for major subtypes of inhibitory ion channel receptors.
Spatial and cortical influences exerted on cuneothalamic and thalamocortical neurons of the cat
Authors: Canedo Antonio , Aguilar Juan
Published: March 2003

This work aimed to study the responses of cuneothalamic and thalamocortical cells to electrical stimulation of the body surface in α‐chloralose‐anaesthetized cats. It was found that both classes of cells had a central excitatory receptive field, an edge overlapping the field centre whose stimulation elicited inhibitory–excitatory (cuneothalamic cells) and excitatory–inhibitory (thalamocortical cells) sequences, and a surrounding or peripheral area usually being inhibitory. Manipulating the descending corticofugal activity by removing the fronto‐parietal cortex, electrical stimulation, or by placing picrotoxin or muscimol over the sensorimotor cortex demonstrated that the cortical feedback potentiated effects driven from the field centre and the surround. In particular this potentiated centre‐driven excitation and surround‐driven inhibition, but some of the data points to more complex patterns. The inhibition elicited in cuneothalamic cells from the edge and the surround of the field was faster than the excitation induced from the field centre. Effects at the edge of the field centre included late excitatory responses relayed via the cerebral cortex. There were also direct corticofugal excitatory inputs to the field centre. Excitatory surrounds were occasionally observed, the assumption being that in most cases these were suppressed by the enhanced inhibition driven from the cortex. The data indicate that the cortico‐subcortical feedback contributes not only to enhance the surround antagonism of a centre response but also to increase the time resolution of thalamic and cuneate relay somesthetic neurons.
Synaptic plasticity in the basolateral amygdala in transgenic mice expressing dominant‐negative cAMP response element‐binding protein (CREB) in forebrain
Authors: Rammes G. , Steckler T. , Kresse A. , Schütz G. , Zieglgänsberger W. , Lutz B.
Published: March 2003

Electrophysiological and behavioural experiments were performed in transgenic mice expressing a dominant‐negative form of cAMP response element‐binding protein (CREBA133) in the limbic system. In control littermate in vitro slice preparation, tetanizing the lateral amygdala–basolateral amygdala (BLA) pathway with a single train (100 Hz for 1 s) produced short‐term potentiation (STP) in the BLA. Five trains (10‐s interstimulus interval) induced long‐term potentiation (LTP), which was completely blocked by the N‐methyl‐d‐aspartate (NMDA) receptor antagonist d(–)‐2‐amino‐5‐phosphonopentanoic acid (AP5; 50 μm). When GABAergic (γ‐aminobutyric acid) inhibition was blocked by picrotoxin (10 μm), LTP became more pronounced. Low‐frequency stimulation (1 Hz for 15 min) induced either long‐term depression (LTD) or depotentiation. LTD remained unaffected by AP5 (50 μm) or by the L‐ and T‐type Ca2+‐channel blockers nifedipine (20 μm) and Ni2+ (50 μm), but was prevented by picrotoxin (10 μm), indicating a GABAergic link in the expression of LTD in the BLA. When conditioned fear was tested, a mild impairment was seen in one of three transgenic lines only. Although high levels of mRNA encoding CREBA133 lead to downregulation of endogenous CREB, expression of LTP and depotentiation were unaltered in BLA of these transgenic animals. These results could suggest that residual CREB activity was still present or that CREB per se is dispensable. Alternatively, other CREB‐like proteins were able to compensate for impaired CREB function.
The chondroitin sulphate proteoglycan brevican is upregulated by astrocytes after entorhinal cortex lesions in adult rats
Authors: Thon Niklas , Haas Carola A. , Rauch Uwe , Merten Tobias , Fässler Reinhard , Frotscher Michael , Deller Thomas
Published: March 2003

The chondroitin sulphate proteoglycan brevican is one of the most abundant extracellular matrix molecules in the adult rat brain. It is primarily synthesized by astrocytes and is believed to influence astroglial motility during development and under certain pathological conditions. In order to study a potential role of brevican in the glial reaction after brain injury, its expression was analysed following entorhinal cortex lesion in rats (12 h, 1, 2, 4, 10, 14 and 28 days and 6 months post lesion). In situ hybridization and immunohistochemistry were employed to study brevican mRNA and protein, respectively, in the denervated outer molecular layer of the fascia dentata and at the lesion site. In both regions brevican mRNA was upregulated between 1 and 4 days post lesion. The combination of in situ hybridization with immunohistochemistry for glial fibrillary acidic protein demonstrated that many brevican mRNA‐expressing cells are astrocytes. In the denervated zone of the fascia dentata, immunostaining for brevican was increased by 4 days, reached a maximum by 4 weeks and remained detectable up to 6 months post lesion. Electron microscopic immunocytochemistry showed that brevican is a component of the extracellular matrix compartment. At the lesion site a similar time course of brevican upregulation was observed. These data demonstrate that brevican is upregulated in areas of brain damage as well as in areas denervated by a lesion. They suggest a role of brevican in reactive gliosis and are compatible with the hypothesis that brevican is involved in the synaptic reorganization of denervated brain areas.
Role of the peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) and its natural ligand 15‐deoxy‐Δ12,14‐prostaglandin J2in the regulation of microglial functions
Authors: Bernardo Antonietta , Levi Giulio , Minghetti Luisa
Published: March 2003

The peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) is a member of a large group of nuclear receptors controlling the proliferation of peroxisomes that is involved in the downregulation of macrophage functions. Here, we report that PPAR‐γ was constitutively expressed in rat primary microglial cultures and that such expression was downregulated during microglial activation by endotoxin (LPS). The presence of the PPAR‐γ natural ligand 15‐deoxy‐Δ12,14‐prostaglandin J2(15d‐PGJ2) counteracted the repression of PPAR‐γ expression caused by LPS. In microglial cultures stimulated by LPS, interferon‐γ (IFN‐γ) or by their combination, 15d‐PGJ2reduced the production of nitric oxide (NO) and the expression of inducible NO synthase (iNOS). The inhibitory effect was dose‐dependent and did not involve an elevation of cyclic AMP, a second messenger known to inhibit NOS expression in microglia. In addition, 15d‐PGJ2down‐regulated other microglial functions, such as tumour necrosis factor‐α (TNF‐α) synthesis and major histocompatibility complex class II (MHC class II) expression. The effects of 15d‐PGJ2occurred, at least in part, through the repression of two important transcription factors, the signal transducer and activator of transcription 1 and the nuclear factor κB, known to mediate IFN‐γ and LPS cell signalling. Our observations suggest that 15d‐PGJ2, the synthesis of which is likely to occur within the brain, could play an important role in preventing brain damage associated with excessive microglial activation.
Glucocorticoid receptor impairment enhances impulsive responding in transgenic mice performing on a simultaneous visual discrimination task
Authors: Steckler Thomas , Sauvage Magdalena , Holsboer Florian
Published: March 2003

Transgenic mice with impaired glucocorticoid receptor (GR) function were tested for their ability to learn and perform a series of simultaneous visual discriminations which allowed a dissociation between accuracy of discrimination from those of motivation and behavioural disinhibition. Animals were first trained on an operant five‐choice simultaneous discrimination autoshaping procedure, followed by a continuous reinforcement schedule on that task. Subsequently, the number of choices was limited to two and data were analysed according to the mathematical methods of signal detection theory (SDT). The effects of GR‐antisense expression on accuracy when different rates of responding were required were studied under different fixed ratio response requirements (FR1–FR10). Autoshaping was retarded in transgenic animals and accuracy was impaired in both the five‐choice and the two‐choice discrimination tasks, although transgenic mice showed clear evidence for learning. Under conditions of low response requirements, transgenic mice showed increased response and cognitive biases, but reduced perceptual bias, and a behavioural disinhibition, characterized by a reduction in errors of omission, decreased response latencies and increased number of responses during the inter‐trial interval. Increasing the response requirement improved performance in transgenic animals as reflected by enhanced accuracy. Moreover, transgenics were less susceptible to the deleterious effects of higher response requirements, as indicated by relatively unaffected bias measures in this group, while bias increased in controls. These results indicate that altered performance in GR‐antisense transgenic animals cannot simply be interpreted as a mnemonic deficit, but that altered motivation and enhanced impulsive responding may account for some of these impairments.
Localization and targeting of SCG10 to the trans‐Golgi apparatus and growth cone vesicles
Authors: Lutjens Robert , Igarashi Michihiro , Pellier Veronique , Blasey Horst , Di Paolo Gilbert , Ruchti Evelyne , Pfulg Claudine , Staple Julie K. , Catsicas Stefan , Grenningloh Gabriele
Published: March 2003

SCG10 is a membrane‐associated, microtubule‐destabilizing protein of neuronal growth cones. Using immunoelectron microscopy, we show that in the developing cortex of mice, SCG10 is specifically localized to the trans face Golgi complex and apparently associated with vesicular structures in putative growth cones. Consistent with this, subcellular fractionation of rat forebrain extracts demonstrates that the protein is enriched in the fractions containing the Golgi apparatus and growth cone particles. In isolated growth cone particles, SCG10 was found to be particularly concentrated in the growth cone vesicle fraction. To evaluate the molecular determinants of the specific targeting of SCG10 to growth cones, we have transfected PC12 cells and primary neurons in culture with mutant and fusion cDNA constructs. Deletion of the amino‐terminal domain or mutations within this domain that prevented palmitoylation at cysteines 22 and 24 abolished Golgi localization as well as growth cone targeting, suggesting that palmitoylation of the amino‐terminal domain is a necessary signal for Golgi sorting and possibly transport of SCG10 to growth cones. Fusion proteins consisting of the amino‐terminal domain of SCG10 and the cytosolic proteins stathmin or glutathione‐S‐transferase colocalized with a Golgi marker, α‐mannosidase II, and accumulated in growth cones of both axons and dendrites. These results reveal a novel axonal/dendritic growth cone targeting sequence that involves palmitoylation.
No effect of apolipoprotein E on neuronal cell death due to excitotoxic and apoptotic agents in vitro and neonatal hypoxic ischaemia in vivo
Authors: Lendon Corinne L. , Han Byung Hee , Salimi Kayvon , Fagan Anne M. , Behrens Maria I. , Muller Maureen C. , Holtzman David M.
Published: March 2003

The ε4 allele of apolipoprotein E (apoE) is a genetic risk factor for Alzheimer's disease. Studies also suggest that the ε4 allele may be a risk factor for poor outcome following head trauma, brain haemorrhage and ischaemia. The mechanism by which the presence of an apoE ε4 allele and certain brain injuries act to predispose to Alzheimer's disease and poor outcome following brain injury is unknown. We questioned whether poor outcome after brain injury was due to direct modification by apoE protein and its gene variants of susceptibility to glutamate‐mediated excitotoxic injury and apoptosis, mechanisms of cell death which occur following ischaemia and trauma. We investigated the effect of the presence or absence of endogenous murine apoE protein and different apoE isoforms in modification of the survival of murine embryonic cortical neurons exposed to the glutamate agonist, N‐methyl‐ d‐aspartic acid (NMDA) or apoptotic insult by staurosporine, and on the amount of brain injury sustained following a hypoxic‐ischaemic insult in vivo to the brain of neonatal mice transgenically expressing human apoE ε3 or ε4. Our data provide evidence that apoE does not appear to alter neuronal viability following diverse types of acute neuronal insult, e.g. hypoxic‐ischaemic or acute exposure to injurious agents in the models we have examined. This suggests that if apoE does modify the extent of brain damage and recovery after injury, it seems unlikely to be a result of direct or indirect modulation of excitotoxic or apoptotic cell death.
The accuracy of sound duration representation in the human brain determines the accuracy of behavioural perception
Authors: Amenedo Elena , Escera Carles
Published: March 2003

In recent years, the links between neural activity and perception have been an area of interest in cognitive neuroscience. Combined psychophysiological and psychophysical experiments provide a new powerful tool for establishing the relationship between neural activity and perceptual performance. In animals, intracellular recordings combined with psychophysical detection indices have revealed that a particular neuron or set of neurons can play a critical role in the generation of a perceptual event, showing detection functions (referred to as neurometric functions) which are remarkably similar to psychophysical detection functions, or psychometric functions (Parker & Newsome, (1998) Annu. Rev. Neurosci., 21, 227–277). As noninvasive techniques for recording neural activity are now available, studies combining neuroelectric and psychophysical measures in humans are sparse. In the present study, the accuracy of the human brain in detecting differences in sound duration and the subject's ability to perceive the same differences were tested by means of mismatch negativity (MMN) and the distance between the distributions of false alarms and hits (sensitivity index d′), respectively. It was found that the accuracy of the human auditory system to represent sound duration information is related to the duration context in which the sounds are heard, and that these contextual representations determine the accuracy of perception at the behavioural level.
Deficits of spatial and non‐spatial memory and of auditory fear conditioning following anterior thalamic lesions in mice: comparison with chronic alcohol consumption
Authors: Célérier Aurélie , Ognard Raphaël , Decorte Laurence , Beracochea Daniel
Published: March 2003

This study was aimed at determining (i) whether or not bilateral subtotal lesions of the anterior thalamic nuclei (ATH) in rodents produced memory deficits for spatial and/or non‐spatial information and of auditory fear conditioning, and (ii) if these eventual deficits resemble those produced by chronic alcohol consumption (CAC). Working memory was assessed using both spatial (spontaneous alternation) and non‐spatial (temporal alternation) delayed response tasks. Results showed that ATH lesions induced delay‐dependent memory impairments in both spatial and non‐spatial alternation tasks, as well as a decreased level of auditory and background contextual fear conditioning compared with respective controls. CAC did not induce accelerated rate of forgetting in the spatial and non‐spatial tasks, but increased the vulnerability to interference in the spatial task. CAC impaired only background contextual fear conditioning. We conclude that ATH nuclei are involved in the maintenance of information over time, regardless of the nature (spatial vs. non‐spatial) of the information, and play a role in associative processes for both unimodal (the tone) and polymodal (contextual) information. In contrast, ATH dysfunction does not account for the memory disorders induced by the CAC treatment. Our results contribute to showing that the functional overlap between the structures comprising the hippocampo‐mamillo‐thalamic pathway is only partial.
VIP and PACAP potentiation of nicotinic ACh‐evoked currents in rat parasympathetic neurons is mediated by G‐protein activation
Authors: Liu Dong‐Mei , Cuevas Javier , Adams David J.
Published: March 2003

The effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase‐activating polypeptide (PACAP27 and PACAP38) on isolated parasympathetic neurons of rat intracardiac and submandibular ganglia were examined under voltage clamp using whole‐cell patch‐clamp recording techniques. VIP and PACAP (≤ 10 n m) selectively and reversibly increased the affinity of nicotinic acetylcholine receptor channels (nAChRs) for their agonists resulting in a potentiation of acetylcholine (ACh)‐evoked whole‐cell currents at low agonist concentrations. VIP‐induced potentiation was observed with either ACh or nicotine as the cholinergic agonist. The VIP‐ but not the PACAP‐induced potentiation of ACh‐evoked currents was inhibited by [Ac‐Tyr1, D‐Phe2]‐GRF 1–29, amide (100 nm), a selective antagonist of VPAC1 and VPAC2 receptors; whereas the PACAP38‐ but not the VIP‐induced potentiation was inhibited by 100 nm PACAP6–38, a PAC1 and VPAC2 receptor antagonist. The signal transduction pathway mediating VIP‐ and PACAP‐induced potentiation of nicotinic ACh‐evoked currents involves a pertussis toxin (PTX)‐sensitive G‐protein. Intracellular application of 200 μm GTPγS or GDPβS inhibited VIP‐induced potentiation of ACh‐evoked whole‐cell currents. GTPγS alone potentiated ACh‐ and nicotine‐evoked currents and the magnitude of these currents was not further increased by VIP or PACAP. The G‐protein subtype modulating the neuronal nAChRs was examined by intracellular dialysis with antibodies directed against αo, αi‐1,2, αi‐3 or β G‐protein subunits. Only the anti‐Gαo and anti‐Gβ antibodies significantly inhibited the effect of VIP and PACAP on ACh‐evoked currents. The potentiation of ACh‐evoked currents by VIP and PACAP may be mediated by a membrane‐delimited signal transduction cascade involving the PTX‐sensitive Go protein.
Long‐term consequences of early postnatal seizures on hippocampal learning and plasticity
Authors: Lynch Michael , Sayin Ümit , Bownds Jonathan , Janumpalli Sridevi , Sutula Thomas
Published: March 2003

Neural activity influences the patterning of synaptic connections and functional organization of developing sensory and motor systems, but the long‐term consequences of intense neural activity such as seizures in the developing hippocampus are not adequately understood. To evaluate the possibility that abnormal neural activity during early development may have long‐term functional effects in hippocampal circuitry that plays a role in learning, memory and epilepsy, functional properties of hippocampal circuitry were assessed in adult rats that had experienced seizures induced by kainic acid on specific days during early postnatal development. Although previous studies have suggested that the immature hippocampus is relatively resistant to seizure‐induced alterations compared with adults, independent behavioural and physiological experiments demonstrated that seizures evoked by kainic acid during early postnatal development induced a long‐term loss of hippocampal plasticity manifesting as reduced capacity for long‐term potentiation, reduced susceptibility to kindling, and impaired spatial learning, which was associated with enhanced paired‐pulse inhibition in the dentate gyrus. The enhancement of inhibition and loss of plasticity were maximal when the seizures occurred on the first day of life, but were also observed when seizures were induced as late as postnatal day 14, which delimited a period of postnatal susceptibility in the developing rat hippocampus when disruption of normal neural activity by seizures produced consistent effects on a hippocampal‐dependent behaviour and several forms of hippocampal plasticity implicated in learning, memory and the development of epilepsy in adulthood.
Pituitary adenylate cyclase‐activating polypeptide promotes the survival of basal forebrain cholinergic neurons in vitro and in vivo: comparison with effects of nerve growth factor
Authors: Takei Nobuyuki , Torres Eduardo , Yuhara Aki , Jongsma Helen , Otto Christiane , Korhonen Laura , Abiru Yasuhiro , Skoglösa Ylva , Schütz Günther , Hatanaka Hiroshi , Sofroniew Michael V. , Lindholm Dan
Published: March 2003

Pituitary adenylate cyclase‐activating polypeptide (PACAP) is a member of the vasointestinal polypeptide gene family for which neurotrophic activity has been postulated. PACAP mRNA is expressed in the developing and adult hippocampus, which is the principal target region of septal cholinergic neurons. We therefore studied the effects of PACAP on septal cholinergic neurons. In primary cultures from septum of embryonic and postnatal rats, PACAP increased the number of neurons immunohistochemically stained for the low‐affinity nerve growth factor (NGF) receptor p75 and for the enzyme choline acetyltransferase (ChAT). PACAP also caused a corresponding increase in ChAT activity. In comparison, NGF had a greater effect than PACAP on the number of p75‐ and ChAT‐positive neurons in these cultures. In vivo, following fimbria fornix transection, the number of immunohistochemically stained septal cholinergic neurons fell significantly to 18% in rats given continuous intracerebroventricular infusion of vehicle, whereas in rats given NGF the number of these neurons did not differ significantly from unoperated controls. In PACAP‐treated rats the number was 48% of unoperated values, which represented a significant increase compared with vehicle‐treated rats and a significant decrease compared with NGF‐treated rats or unoperated controls. Double‐staining experiments revealed that most ChAT‐positive neurons in rat medial septum also express PACAP receptor 1. Together the results show that PACAP promotes the survival of septal cholinergic neurons in vitro, and after injury in vivo, suggesting that PACAP acts as a neurotrophic factor influencing the development and maintenance of these neurons.
Deafferentation‐induced apoptosis of neurons in thalamic somatosensory nuclei of the newborn rat: critical period and rescue from cell death by peripherally applied neurotrophins
Authors: Baldi Alfonso , Calia Eustachio , Ciampini Alessandro , Riccio Massimo , Vetuschi Antonella , Persico Antonio M. , Keller Flavio
Published: March 2003

This study shows that unilateral transection of the infraorbital nerve (ION) in newborn (P0) rats induces apoptosis in the contralateral ventrobasal thalamic (VB) complex, as evidenced by terminal transferase‐mediated deoxyuridine triphosphate‐biotin nick end labelling (TUNEL) and electron miscroscopy. Double‐labelling experiments using retrograde transport of labelled microspheres injected into the barrel cortex, followed by TUNEL staining, show that TUNEL‐positive cells are thalamocortical neurons. The number of TUNEL‐positive cells had begun to increase by 24 h postlesion, increased further 48 h after nerve section, and decreased to control levels after 120 h. Lesion‐induced apoptosis in the VB complex is less pronounced if ION section is performed at P4, and disappears if the lesion is performed at P7. This time course closely matches the critical period of lesion‐induced plasticity in the barrel cortex. Nerve growth factor (NGF) or brain‐derived neurotrophic factor (BDNF), applied on the ION stump alone or in combination, are able to partially rescue thalamic neurons from apoptosis. Total cell counts in the VB complex of P7 animals that underwent ION section at P0 confirm the rescuing effect of BDNF and NGF. Blockade of axonal transport in the ION mimics the effect of ION section. These data suggest that survival‐promoting signals from the periphery, maybe neurotrophins, are required for the survival of higher‐order neurons in the somatosensory system during the period of fine‐tuning of neuronal connections. We also propose that anterograde transneuronal degeneration in the neonatal rat trigeminal system may represent a new animal model for studying the pathways of programmed cell death in vivo.
Differential effect of oestradiol and astroglia‐conditioned media on the growth of hypothalamic neurons from male and female rat brains
Authors: Cambiasso M. J. , Colombo J. A. , Carrer H. F.
Published: March 2003

To determine whether soluble products from different CNS regions differ in their ability to support oestrogen‐stimulated neurite growth, hypothalamic neurons from sexually segregated embryos were cultured with astroglia‐conditioned medium (CM) derived from cortex, striatum and mesencephalon, with or without 17‐β‐oestradiol 100 n m added to the medium. After 48 h in vitro, neurite outgrowth was quantified by morphometric analysis. Astroglia‐CM from mesencephalon (a target for the axons of hypothalamic neurons) induced the greatest axogenic response in males and in this case only a neuritogenic effect could be demonstrated for oestradiol. On the other hand, astroglia‐CM from regions that do not receive projections from ventromedial hypothalamus inhibited axon growth. A sexual difference in the response of hypothalamic neurons to astroglia‐CM and oestradiol was found; growth of neurons from female foetuses was increased by astroglia‐CM from mesencephalon, but no neuritogenic effect could be demonstrated for oestradiol in these cultures. Blot immunobinding demonstrated the presence of receptors for neurotrophic factors in cultures of hypothalamic neurons; Western blot analysis of these cultures demonstrated that oestradiol increased the concentration of trkB and IGF‐I Rβ, whereas trkA was not detected and the concentration of trkC was not modified. These results support the hypothesis that target regions produce some factor(s) that stimulate the growth of axons from projecting neurons and further indicate that in the case of males this effect is modulated by oestradiol, perhaps mediated through the upregulation of trkB and IGF‐I receptors.
Species‐specific modulation of pattern‐generating circuits
Authors: Meyrand Pierre , Faumont Serge , Simmers John , Christie Andrew E. , Nusbaum Michael P.
Published: March 2003

Phylogenetic comparison can reveal general principles governing the organization and neuromodulation of neural networks. Suitable models for such an approach are the pyloric and gastric motor networks of the crustacean stomatogastric ganglion (STG). These networks, which have been well studied in several species, are extensively modulated by projection neurons originating in higher‐order ganglia. Several of these have been identified in different decapod species, including the paired modulatory proctolin neuron (MPN) in the crab Cancer borealis [Nusbaum & Marder (1989) J. Neurosci., 9,1501–1599; Nusbaum & Marder (1989), J. Neurosci., 9, 1600–1607] and the apparently equivalent neuron pair, called GABA (γ‐aminobutyric acid) neurons 1 and 2 (GN1/2), in the lobster Homarus gammarus [Cournil et al. (1990) J. Neurocytol., 19, 478–493]. The morphologies of MPN and GN1/2 are similar, and both exhibit GABA‐immunolabelling. However, unlike MPN, GN1/2 does not contain the peptide transmitter proctolin. Instead, GN1/2, but not MPN, is immunoreactive for the neuropeptides related to cholecystokinin (CCK) and FLRFamide. Nonetheless, GN1/2 excitation of the lobster pyloric rhythm is similar to the proctolin‐mediated excitation of the crab pyloric rhythm by MPN. In contrast, GN1/2 and MPN both use GABA but produce opposite effects on the gastric mill rhythm. While MPN stimulation produces a GABA‐mediated suppression of the gastric rhythm [Blitz & Nusbaum (1999) J. Neurosci., 19, 6774–6783], GN1/2 activates or enhances gastric rhythmicity. These results highlight the care needed when generalizing neuronal organization and function across related species. Here we show that the ‘same’ neuron in different species does not contain the same neurotransmitter complement, nor does it exert all of the same effects on its postsynaptic targets. Conversely, a different transmitter phenotype is not necessarily associated with a qualitative change in the way that a modulatory neuron influences target network activity.
Elevation of intradendritic sodium concentration mediated by synaptic activation of metabotropic glutamate receptors in cerebellar Purkinje cells
Authors: Knöpfel T. , Anchisi D. , Alojado M. E. , Tempia F. , Strata P.
Published: March 2003

Cerebellar Purkinje cells express both ionotropic glutamate receptors and metabotropic glutamate receptors. Brief tetanic stimulation of parallel fibers in rat and mouse cerebellar slices evokes a slow excitatory postsynaptic current in Purkinje cells that is mediated by the mGluR1 subtype of metabotropic glutamate receptors. The effector system underlying this mGluR1 EPSC has not yet been identified. In the present study, we recorded the mGluR1 EPSC using the whole‐cell patch‐clamp technique in combination with microfluorometric recordings of the intracellular sodium concentration ([Na+]i) by means of the fluorescent sodium indicator SBFI. The mGluR1 EPSC was induced by local parallel fibre stimulation in the presence of the ionotropic glutamate receptor antagonists NBQX and D‐APV and the GABAA receptor antagonists bicuculline or picrotoxin. The mGluR1 EPSC was associated with an increase in [Na+]i that was restricted to a specific portion of the dendritic tree. The mGluR1 EPSC as well as the increase in [Na+]i were inhibited by the mGluR antagonist S‐MCPG. In the presence of NBQX, D‐APV, pictrotoxin and TTX, bath application of the selective mGluR agonist 3,5‐DHPG induced an elevation in [Na+]i which extended over the whole dendritic field of the Purkinje cell. This finding demonstrates that the mGluR1‐mediated postsynaptic current leads to a significant influx of sodium into the dendritic cytoplasm of Purkinje cells and thereby provides a novel intracellular signalling mechanism that might be involved in mGluR1‐dependent synaptic plasticity at this synapse.
Time‐dependent enhancement of inhibitory avoidance retention and MAPK activation by post‐training infusion of nerve growth factor into CA1 region of hippocampus of adult rats
Authors: Walz Roger , Lenz Guido , Roesler Rafael , Vianna Mônica M. R. , Martins Vilma , Brentani Ricardo , Rodnight Richard , Izquierdo Ivan
Published: March 2003

Several studies have demonstrated that chronic intracerebroventricular nerve growth factor (NGF) infusion has a beneficial effect on cognitive performance of lesioned as well as old and developing animals. Here we investigate: (i) the effect of post‐training infusion of NGF into the CA1 region of hippocampus on inhibitory avoidance (IA) retention in rats; (ii) the extension of the effect, in time and space, of NGF infusion into CA1 on the activity of mitogen‐activated protein kinase (MAPK, syn: ERK1/2, p42/p44 MAPK). NGF was bilaterally injected into the CA1 regions of the dorsal hippocampus (0.05, 0.5 or 5.0 ng diluted in 0.5 μL of saline per side) at 0, 120 or 360 min after IA training in rats. Retention testing was carried out 24 h after training. The injection of 5.0 and 0.5, but not 0.05, ng per side of NGF at 0 and 120 min after IA training enhanced IA retention. The highest dose used was ineffective when injected 360 min after training. The infusion of 0.5 μL of NGF (5.0 ng) induced a significant enhancement of MAPK activity in hippocampal microslices; this enhancement was restricted to a volume with 0.8 mm radius at 30 min after injection. The MAPK activation was still seen 180 min after NGF infusion, although this value showed only a tendency. In conclusion, localized infusion of NGF into the CA1 region enhanced MAPK activity, restricted in time and space, and enhanced IA retention in a time‐ and dose‐dependent manner.