bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epidermal Growth Factor Prevents Oxygen‐triggered Apoptosis and Induces Sustained Signalling in Cultured Rat Cerebral Cortical Neurons
Authors: Yamada Masashi , Enokido Yasushi , Ikeuchi Toshihiko , Hatanaka Hiroshi 
Published: April 2006

AbstractEpidermal growth factor (EGF), a conventional mitogenic factor, acts as a neurotrophic factor on several types of neurons in the central nervous system. We found that EGF prevented the death of rat cerebral cortical neurons cultured in a 50% oxygen atmosphere. This high‐oxygen‐triggered cell death showed features of apoptotic cell death, which was blocked by inhibitors of RNA or protein synthesis. EGF prevented the oxygen‐induced death of the cultured cortical neurons in a dose‐dependent manner. Basic fibroblast growth factor (bFGF) also prevented this cell death, although there was no apparent additive effect of EGF and bFGF. Among the cultured cortical neurons, we observed neurons possessing the EGF receptor and cells expressing c‐Fos protein in response to EGF. The cortical neurons were cultured in the presence of cytosine arabinoside, and the number of glial fibrillary acidic protein‐positive astroglial cells was >0.5% of that of the corresponding microtubule‐associated protein 2‐positive neurons. Therefore, the effect of EGF on the cultured cortical neurons is thought to be due to a direct action. We also examined EGF‐induced signalling in the cultured cortical neurons. We found that EGF induced the sustained tyrosine phosphorylation of the EGF receptor and sustained the activation of mitogen‐activated protein kinase in the cultured cortical neurons. We suggest that EGF may exert the survival effect through the prolonged activation of the EGF signalling.
Dopamine‐Glutamate‐GABA Interactions and Ageing: Studies in the Striatum of the Conscious Rat
Authors: Porras Alberto , Mora Francisco 
Published: April 2006

AbstractThe effects of apomorphine, a D1–D2 dopamine receptor agonist, on the extracellular concentrations of glutamate and GABA were investigated in the striatum of young, middle‐aged and aged rats. In vivo intracerebral perfusions were undertaken in the conscious rat using a concentric push‐pull cannula system. Amino acid concentrations in samples were determined by HPLC with fluorometric detection. Apomorphine produced a concentration‐related rise in striatal glutamate and GABA concentrations in young rats. Maximal increases were obtained at 20 μM apomorphine, and concentrations reached 184 and 191% of the basal value for glutamate and GABA respectively. Apomorphine failed to produce similar increases in glutamate concentration in middle‐aged and aged rats. Apomorphine, at 10 μM, also failed to produce an increase in GABA concentration in the aged rat. However, at 20 μM apomorphine produced increases in GABA concentration in middle‐aged and aged rats similar to those produced in young rats. These data are indicative of a change in threshold for GABA release induced by dopamine receptor stimulation in the aged rat. These results indicate that an interaction among dopamine, glutamate and GABA exists in the striatum of the rat, and that this type of interaction deteriorates with age.
Inertial, Substratal and Landmark Cue Control of Hippocampal CA1 Place Cell Activity
Authors: Wiener Sidney I. , Korshunov Victor A. , Garcia René , Berthoz Alain 
Published: April 2006

AbstractHippocampal ‘place cells’ discharge when a rat occupies a location that is fixed in relation to environmental landmarks. A principal goal of this study was to determine whether hippocampal place cell activity could be influenced by inertial cues. Water‐deprived rats were trained in a square‐walled open field in a dark room. The behavioural task required alternating visits to water reservoirs in the centre and in the four corners of the arena. The rat and arena were rotated in total darkness through ±90, 180 or 270°. The next water reward was then presented in the corner at the same position relative to the outside room as before the rotation. A cue card was later illuminated in this corner as a visual cue for the extra‐arena (room) reference frame. Fifteen out of 97 recorded hippocampal CA1 complex spike cells had spatially selective discharges in non‐central parts of the arena. After arena rotations, the firing fields of three units shifted between corners of the arena to maintain a fixed orientation relative to the room. This indicates that the hippocampus updated its representation of the position and heading direction of the rat using vestibular‐derived inputs concerning rotation angle. Other spatially selective discharges were guided to landmark cues (cue card or position of the reward: two units) or arena‐locked ‘substratal’ cues (eight units). In six cells, place cell activity suddenly ceased or appeared following rotations. These results provide evidence for contributions of inertial as well as substratal and landmark information to hippocampal spatial representations.
Targeted Delivery of Nerve Growth Factor via Fibronectin Conduits Assists Nerve Regeneration in Control and Diabetic Rats
Authors: Whitworth Ian H. , Terenghi Giorgio , Green Colin J. , Brown Robert A. , Stevens Elizabeth , Tomlinson David R. 
Published: April 2006

AbstractThis study examined the influence of fibronectin conduits joining two halves of a sectioned sciatic nerve, with and without preimpregnation with nerve growth factor, on regeneration in rats with streptozotocin‐induced diabetes mellitus. Regeneration, measured morphometrically in fibres containing immunoreactivity to calcitonin gene‐related peptide (CGRP) and GAP‐43, was significantly less (P < 0.0001 for all comparisons) in diabetic rats with fibronectin mat grafts without nerve growth factor compared to similarly treated controls. Regeneration distances in diabetic rats were reduced to 43% (CGRP‐reactive fibres) and 44% (GAP‐43‐reactive fibres) of controls, and the total amounts of immunoreactivities in the conduits were also reduced, though by lesser amounts (55 and 61% of controls respectively). Impregnation of the conduits with nerve growth factor before implantation increased the distance and amounts of regenerating immunoreactivity in both control and diabetic rats for both CGRP and GAP‐43, such that these regeneration parameters were similar in nerve growth factor‐treated diabetic rats to those in control rats implanted with untreated fibronectin mat conduits. These findings implicate impaired neurotrophic support in the defective regeneration characteristic of diabetic neuropathy.
The Nitric Oxide/cGMP System in the Antennal Lobe of Apis mellifera is Implicated in Integrative Processing of Chemosensory Stimuli
Authors: Müller Uli , Hildebrandt Herbert 
Published: April 2006

AbstractThe high concentration and the localization of nitric oxide synthase in the olfactory system of both vertebrates and invertebrates suggest that the diffusible messenger nitric oxide plays a central role in the processing of chemosensory information. This paper describes the nitric oxide releasing system in the antenna and the antennal lobes of Apis mellifera using the NADPH diaphorase technique, and analyses the contribution of the nitric oxide system in the neuronal processing of chemosensory signals using a behavioural assay in vivo. In the antenna the strongest NADPH diaphorase staining is found in non‐neuronal auxiliary and/or epithelial cells, while the sensory cells and the antennal nerve are stained at a low level. At the major site of chemosensory signal integration, the antennal lobes, the highest nitric oxide synthase activity is located in the glomeruli, which are ideally suited to act as diffusion compartments. We demonstrate that inhibition of nitric oxide synthase in the antennal lobes specifically interferes with neuronal processing of repetitive chemosensory stimuli but does not affect the response to single stimuli, and is independent of parameters such as satiation level, stimulus strength, interstimulus interval and duration of sensory stimuli. Since inhibition of the soluble guanylate cyclase, a major target of nitric oxide, also particularly affects the adaptive component, the physiological effects of nitric oxide appear to be mediated by the action of cGMP. These findings suggest that the nitric oxide/cGMP system in the antennal lobes is a component of the molecular machinery involved in adaptive and/or integrative mechanisms during chemosensory information processing in vivo.
Nucleus Reticularis Thalami and Neocortical Paroxysms in the Rat
Authors: Marini Gabriella , Giglio Roberto , Macchi Giorgio , Mancia Mauro 
Published: April 2006

AbstractThe role of the nucleus reticularis thalami in spike‐wave discharges in rats with genetic absence epilepsy has already been demonstrated. This study further investigated the role of the nucleus reticularis thalami in paroxysmal synchronizations in Sprague‐Dawley rats; this strain shows no propensity to epileptic activity. Electroencephalographic patterns were followed in chronically implanted, unrestrained rats. After both electrolytic and chemical unilateral lesions, stereotaxically placed in the anterolateral sectors of this nucleus (verified post mortem), abnormal electroencephalographic rhythms (high‐voltage polyspikes and spike‐wave complexes) were recorded from the frontoparietal cortex, primarily in the contralateral hemisphere. Stereotyped discharges at 3 Hz developed progressively from multiple spikes within the alpha frequency range through the lengthening of the wave component. The excessive synchronized activity recorded from the intact hemisphere was of greater amplitude and occurred slightly earlier than from the lesioned hemisphere. These EEG patterns were associated with behavioural manifestations closely resembling those seen during absence seizures in humans. Bilateral lesions did not induce paroxysmal activity, both hemispheres being characterized by dominant delta/theta activity without signs of EEG‐synchronized sleep. The seizures may thus have been due to disinhibition of the contralateral reticularis nucleus, recently shown to project to the reticularis nucleus of the other side in rats. This working hypothesis is supported by callosal cuts. The results indicate that the reticular neurons exert a control over neocortical paroxysmal activity even in animals which do not present genetic absence epilepsy.
Receptive Field Properties of Starburst Cholinergic Amacrine Cells in the Rabbit Retina
Authors: Taylor W. Rowland , Wässle Heinz 
Published: April 2006

AbstractPatch‐clamp recordings were made from ON starburst cholinergic amacrine cells with somas located in the ganglion cell layer of an isolated, dark‐adapted rabbit retina preparation. Light responses were analysed and cell identity was confirmed anatomically. The centre light response had a linear current‐voltage relation with a reversal potential close to 0 mV. The receptive field size was similar to the dendritic field size. Cholinergic amacrine cells displayed significant surround inhibition. The receptive field profile consisted of a central excitatory region flanked by an inhibitory surround. The surround attenuated the central response to 36% of the maximum. The surround was probably mediated by a combination of presynaptic and postsynaptic inhibition. Starburst amacrine cells did not display action potentials and the presence of a large, voltage‐dependent outward current limited depolarizing responses to a maximum potential of about ‐40 mV. Light responses were completely suppressed during application of 100 μM D, L‐2‐amino‐4‐phosphonobutyric acid (APB), consistent with activation exclusively through rod bipolar cells (on) and ON‐cone bipolar cells. In darkness the cells displayed a tonic inward current that could be blocked by 100 μM APB and 2 μM CNQX.
Distinct Temporal Patterns of Expression of Sodium Channel‐like Immunoreactivity During the Prenatal Development of the Monkey and Cat Retina
Authors: Miguel‐Hidalgo José J. , Angelides Kimon J. , Chalupa Leo M. 
Published: April 2006

AbstractPolyclonal and monoclonal antibodies prepared against the α‐subunit of the voltage‐gated sodium channel (αNaCh) were used to examine the distribution of sodium channel‐like immunoreactivity during the prenatal development of the cat and rhesus monkey (Macaca mulatta) retina. At all prenatal ages studied, beginning on embryonic day 29 (E29) in the cat and E52 in the monkey, both antibodies labelled optic axons. With the polyclonal antibodies, the appearance of positive cells largely mirrored the onset of their morphological maturation. Immunoreactivity appeared first in the somata of ganglion cells, and subsequently the inner plexiform layer could be distinguished by its intense immunolabelling. A few weeks later horizontal cells displayed immunolabelling that extended to their dendrites in the developing outer plexiform layer. This was followed by immunoreactive cones, with bipolar cells labelled only postnatally. By contrast, with the monoclonal antibody some cells were found to be immunoreactive while their somata were still in the ventricular layer (E33 in cat and E52 in monkey). Many of these cells appeared to migrate to the outer portion of the prospective inner nuclear layer, where they gradually acquired the morphological appearance of bipolar cells. Transient expression of immunolabelling with monoclonal sodium channel antibody was found in the cones of the cat and cones and rods of the monkey. These results indicate that different types of αNaCh‐like proteins are expressed in the mammalian retina at distinct developmental periods. Their presence at very early stages during development suggests that these proteins could play a specific role in the commitment and/or differentiation of specific retinal cell types.
Interleukin‐1β Stimulates both Central and Peripheral Release of Vasopressin and Oxytocin in the Rat
Authors: Landgraf Rainer , Neumann Inga , Holsboer Florian , Pittman Quentin J. 
Published: April 2006

AbstractSimultaneous microdialysis in the brain and blood was used to monitor the release of vasopressin and oxytocin within the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei and into the systemic circulation of urethane‐anaesthetized male rats before and after central administration of interleukin‐1β (IL‐1β). Following intracerebroventricular infusion of the cytokine (200 ng/5 μl), the content of vasopressin (up to 278% compared to vehicle‐treated control, P < 0.01 compared to vehicle‐treated control and preinfusion baseline) but not oxytocin (up to 148%, not significant) in 30‐min blood microdialysates was found to be increased. This peripheral release was accompanied by a transient rise in vasopressin (up to 163%, P < 0.05) and oxytocin (up to 182%, P < 0.05) release within the SON, the peak typically occurring during the first and second 30‐min collection intervals after IL‐1 β respectively. In contrast, in the simultaneously microdialysed PVN, both vasopressin and oxytocin failed to respond to intracerebroventricular IL‐1 β. In another series of experiments, IL‐1 β was directly infused (20 ng0.5 μl) into either the SON or PVN during microdialysis of the corresponding nucleus. The cytokine caused a significant and immediate rise in intra‐SON release of both vasopressin (up to 225%, P < 0.01) and oxytocin (up to 178%, P < 0.05). Again, in the PVN, nonapeptide release, although tending to be stimulated in response to intranuclear IL‐1 β, failed to reach statistical significance. The cytokine‐induced central and peripheral release pattern appeared to be independent of the rise in body temperature observed after IL‐1 β administration. In a third series of experiments, bilateral administration of IL‐1 β into the SON (20 ng/0.5 μl) failed to alter peripheral release of both vasopressin and oxytocin into the systemic circulation. The increase in central nonapeptide release in response to IL‐1 β shown in this paper supports the hypothesis that at least vasopressin might act to oppose central effects of the cytokine, including those on thermoregulation and behaviour, in this way contributing to the neuroendocrine‐immune dialogue at brain level.
α‐Bungarotoxin‐sensitive Nicotinic Receptors on Bovine Chromaffin Cells: Molecular Cloning, Functional Expression and Alternative Splicing of the α7 Subunit
Authors: García‐Guzmán Miguel , Sala Francisco , Sala Salvador , Campos‐Caro Antonio , Stühmer Walter , Gutiérrez Luis M. , Criado Manuel 
Published: April 2006

AbstractChromaffin cells from the bovine adrenal medulla express α‐bungarotoxin‐sensitive acetylcholine receptors whose subunit composition is unknown. Northern blot analysis showed that the α7 subunit, a main component of these α‐bungarotoxin‐sensitive acetylcholine receptors in avian and rat brain, is expressed in chromaffin cells. The cDNA of this bovine α7 subunit was cloned by polymerase chain reaction amplification of adrenal medulla RNA for detailed characterization of structure and function. The protein‐coding region revealed 92% amino acid sequence identity to rat α7 and 89% to chicken α7 subunits. The α‐bungarotoxin affinity of α7 homomers expressed in Xenopus oocytes was similar to that observed previously with native chromaffin α‐bungarotoxin sensitive acetylcholine receptors. Cross‐linking and sucrose gradient experiments suggested that, like the muscular and neuronal acetylcholine receptors, the α7 receptor has a pentameric structure. Upon activation with nicotinic agonists the α7 receptor exhibited rapidly desensitizing cation currents that were blocked by nicotinic antagonists and showed inward rectification. The amplification of adrenal medulla RNA by reverse transcription polymerase chain reaction methods revealed an alternatively spliced isoform of the bovine α7 subunit, where the exon that codes for the M2 transmembrane segment was skipped during mRNA processing. Oocyte expression of this isoform does not yield functional channels. However, this alternative mRNA exhibits dose‐dependent inhibition of α7 homomer expression when coinjected with the undeleted isoform.
α‐Latrotoxin is a Potent Inducer of Neurotransmitter Release in Torpedo Electric Organ—Functional and Morphological Characterization
Authors: Linial Michal , Llouz Nili , Feinstein Naomi 
Published: April 2006

AbstractIn this report we show that α‐latrotoxin from black widow spider venom is a potent activator of neurotransmitter release in synaptosomes from the Torpedo electric organ. Binding of the purified toxin (5 nM) to the synaptosomal fraction occurs already at 4°C and is dependent on the presence of divalent ions. However, neurotransmitter release commences only after temperature elevation (22°C) and is completed within 2 min. The effect of α‐latrotoxin on release is achieved at 1 nM and is already saturated at 5 nM. The release is stimulated by the presence of Ca2+ ions. Activation of release by α‐latrotoxin is accompanied by morphological changes in electric organ synaptosomes. The synaptosomes swell, resulting in a 55% increase in section area. Moreover, the number of synaptic vesicles per unit area decreases about three‐fold, and rows of docked synaptic vesicles are rarely detected as opposed to control synaptosomes. These morphological changes indicate that the massive release is mainly due to synaptic vesicle fusion. α‐Latrotoxin binding sites are highly concentrated in the innervated face of the electrocytes. lmmunoelectron microscopy on electric organ sections reveals alatrotoxin binding sites over the entire plasma membrane at release sites and facing Schwann cells surrounding Torpedo nerve terminals. Surprisingly, a high concentration of binding sites is also found at structures surrounding branching unmyelinated axons. This staining is in close proximity to Schwann cell envelopes and to the basal lamina around axonal tips. The mode of action of α‐latrotoxin in view of the localization of its binding sites is discussed.
Neuronal Sianallina of Information Imoortant to Visual Recognition‐Memory in Rat Rhinal aid Neighbouring Cortices
Authors: Zhu X. O. , Brown M. W. , Aggleton J. P. 
Published: April 2006

AbstractThis study was conducted to discover whether the rat cortex contains neurons that signal information concerning the previous occurrence of stimuli, as has been found in the primate. Recordings of the activity of 396 single neurons were made while unanaesthetized rats were shown objects. The effects on neuronal responsiveness of stimulus repetition and of the relative familiarity of the stimuli were sought. The areas sampled were the rhinal (entorhinal and perirhinal) cortex, area TE of the temporal cortex, the lateral occipital cortex and the hippocampal formation. The response to the first presentations of objects was significantly different from that to their second presentations for 63 (34%) of the 185 responsive neurons; for 39 of the neurons the response was smaller when the stimulus was repeated, whereas for 24 it was larger. The incidence of decremental responses was higher in the non‐hippocampal cortex than in the hippocampal formation, while the incidence of incremental responses was higher in the hippocampal formation than other cortical areas. The response to unfamiliar objects was significantly different from that to highly familiar objects for 15 (22%) of 67 responsive neurons so tested; for 12 of the neurons the response was smaller when the stimulus was repeated, and for three it was larger; most of these neurons were found in area TE. The responses of ten familiarity neurons varied significantly with the relative familiarity of the stimuli but not with stimulus repetition; the responses of seven recency neurons varied significantly upon stimulus repetition but not with the relative familiarity of the stimuli. Thus information concerning stimulus repetition and familiarity is separably encoded at the single neuron level in the rat cortex. The results demonstrate that in the rat cortex as in the monkey cortex there are neurons that signal information concerning the prior occurrence of stimuli; such information is of importance to recognition memory, working memory and priming memory.