bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dihydrokainate‐sensitive neuronal glutamate transport is required for protection of rat cortical neurons in culture against synaptically released glutamate
Authors: Wang Guang Jian , Chung Hye Joo , Schnuer Jamie , Lea Elizabeth , Robinson Michael B. , Potthoff William K. , Aizenman Elias , Rosenberg Paul A. 
Published: March 2003

AbstractGlutamate transport in nearly pure rat cortical neurons in culture (less than 0.2% astrocytes) is potently inhibited by dihydrokainate, l‐serine‐O‐sulphate, but not by l‐α‐amino‐adipate. This system allows for a test of the hypothesis that glutamate transport is important for protecting neurons against the toxicity of endogenous synaptically released glutamate. In support of this hypothesis, a 20–24 h exposure to 1 mm dihydrokainate reduced cell survival to only 14.8 ± 9.8% in neuronal cultures (P < 0.001;n = 3), although it had no effect on neuronal survival in astrocyte‐rich cultures (P > 0.05;n = 3). Dihydrokainate also significantly caused accumulation of glutamate in the extracellular medium of cortical neuronal cultures (6.6 ± 4.9 μm, compared to 1.2 ± 0.3 μm in control, n = 14, P < 0.01). The neurotoxicity of dihydrokainate was blocked by 10 μm MK‐801, 10 μm tetrodotoxin, and an enzyme system that degrades extracellular glutamate. The latter two also abolished the accumulation of glutamate in the extracellular medium. Dihydrokainate (1 mm) inhibited the 45calcium uptake stimulated by 30 μmN‐methyl‐d‐aspartate (NMDA), but not by higher concentrations consistent with a weak antagonist action of dihydrokainate at the NMDA receptor. Whole cell recordings showed that 1 mm dihydrokainate produced ≈ 25% inhibition of 30 μm NMDA‐induced current in cortical neurons. Dihydrokainate (1 mm) alone generated a small current (17% of the current produced by 30 μm NMDA) that was blocked by 30 μm 5,7‐dichlorokynurenate and only weakly by 10 μm 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX). These results suggest that the toxicity of dihydrokainate in neuronal cultures is due to its ability to block glutamate transport in these cultures, and that dihydrokainate‐sensitive neuronal glutamate transport may be important in protecting neurons against the toxicity of synaptically released glutamate.
Changes in morphology and behaviour of retinal growth cones before and after crossing the midline of the mouse chiasm – a confocal microscopy study
Authors: Chan S. O. , Wong K. F. , Chung K. Y. , Yung W. H. 
Published: March 2003

AbstractThe growth of retinal axons was investigated in different regions of the optic chiasm in C57 pigmented mouse embryos aged embryonic day 13 (E13) to E15. Individual retinal axons and their growth cones were labelled anterogradely by DiI and imaged using a confocal imaging system. In aldehyde‐fixed embryos, retinal growth cones display a simple form in the optic nerve and become more complex in morphology in the chiasm. The complex form is particularly prominent in those axons that turn to the ipsilateral tract in the premidline region of chiasm. Moreover, complex growth cones are also commonly found in axons in the postmidline chiasm, which are markedly different in morphology from those axons in the premidline region, suggesting that the postmidline chiasm contains a novel environment for the pathfinding of retinal axons. In another experiment, the dynamic growth of retinal axons is studied in a brain slice preparation of the living retinofugal pathway. Retinal axons show an intermittent growth across the premidline and postmidline chiasm. Extensive remodelling of growth cone form followed by a shift in growth direction is commonly seen during the pause periods, indicating that signals that guide axon growth across the chiasm are not restricted to the midline, but are laid down throughout the chiasm. Moreover, dramatic changes in axon trajectory are noted first at the premidline chiasm where the uncrossed axons segregate from the crossed axons, and second at the postmidline chiasm where specific sorting of retinal axons according to their position in the dorsal ventral retinal axis and their ages are known to take place. These results show that there are two distinct environments, separated by the midline in the chiasm, where axons show different responses to local guidance cues and develop the distinct fibre orders.
Cellular prion protein localization in rodent and primate brain
Authors: Salès Nicole , Rodolfo Katia , Hässig Raymonde , Faucheux Baptiste , Di Giamberardino Luigi , Moya Kenneth L. 
Published: March 2003

AbstractThe presence of an abnormal, protease‐resistant form of the prion protein (PrP) is the hallmark of various forms of transmissible spongiform encephalopathies (TSE) which can affect a number of mammalian species, including humans. The normal, cellular form of this protein, PrPc, while abundant in brain is also present in many tissues and a number of species. In order to address the unresolved question of the precise localization of normal cerebral PrPc, we used a free‐floating immunohistochemistry procedure to localize the protein at both the light and the electron microscopic levels in the brain of three TSE‐sensitive species: hamster, macaque and humans. This method shows that PrPc is abundant in synaptic terminal fields in olfactory bulb, limbic‐associated structures and in the striato‐nigral complex, whereas many other regions of the hamster brain are essentially devoid of immunoreactivity. With the striking exception of the olfactory nerve, in which axons are continually growing throughout life, PrPc is not abundant in fibre pathways. PrPc distribution in the primate hippocampus and cortex is very similar to the distribution observed in hamster. PrPc was present at synaptic profiles as shown by immunoelectron microscopy, but was not detectable in neuronal perikaryon either by light or electron microscopy. Our results show that PrPc is abundant in a number of brain structures known for ongoing plasticity, and are consistent with the hypothesis that the protein also plays a role in synaptic function.
Human FGF‐1 gene delivery protects against quinolinate‐induced striatal and hippocampal injury in neonatal rats
Authors: Hossain Mir Ahamed , Fielding Kevin E. , Trescher William H. , Ho Tang , Wilson Mary Ann , Laterra John 
Published: March 2003

AbstractFibroblast growth factors (FGFs) are cell mitogens and differentiating factors with neuroprotective properties in the CNS. We have already shown that endothelial cells genetically engineered to secrete human FGF‐1 (RBEZ‐FGF) survive implantation to neonatal rat brain (Johnston et al. (1996) J. Neurochem.67, 1643–1652]. In this study, the effects of cell‐based FGF‐1 gene delivery on quinolinate‐induced neurotoxicity in the developing rat brain were examined. Control endothelial cells (RBE4), and RBEZ‐FGF cells were implanted into right striatum at post‐natal day (PND) 7. On PND 10, quinolinate (150 nmol), an endogenous N‐methyl‐d‐aspartate (NMDA) receptor agonist, or vehicle alone was injected into striatum ipsilateral to cell implantation. Injury was quantified in coronal sections obtained from PND 17 animals by comparing striatal and hippocampal volumes ipsilateral and contralateral to the site of quinolinate injection. Human FGF‐1 specific transgene expression in vivo was shown by Northern blot and RT‐PCR up to 14 days after cell implantation in control animals, and up to 4 days after quinolinate exposure. Quinolinate reduced the size of ipsilateral striatum by 37% and hippocampus by 38% in animals preimplanted with control endothelial cells. In contrast, quinolinate reduced the size of striatum by only 14% and had no effect on hippocampal size in animals preimplanted with RBEZ‐FGF cells. Thus, FGF‐1 gene delivery protected the developing striatum and hippocampus from quinolinate‐induced volume loss by 62% and 100%, respectively. Intrastriatal quinolinate resulted in a significant decrease in density of NOS+ CA3 hippocampal neurons (–38%) without affecting the density of NOS+ neurons in hippocampal regions CA1, dentate gyrus or striatum. This response of CA3 NOS+ neurons appeared to be only partially reversed by FGF‐1 gene delivery. Our results show that intracerebral FGF‐1 gene expression within the developing brain can protect striatum and hippocampus from quinolinate‐mediated injury.
Effects of chronic alcohol consumption or Diazepam administration on item recognition and temporal ordering in a spatial working memory task in mice
Authors: Borde Nathalie , Jaffard Robert , Béracochéa Daniel 
Published: March 2003

AbstractThis study was aimed at determining the effects of either Diazepam administration or chronic alcohol consumption (CAC) on spatial memory measured by concurrent discriminations in an eight arm radial maze using mice as subjects. Two different protocols involving a non‐matching rule were used to evaluate either temporal order (recurrent items) or item recognition (non‐recurrent items). Results showed that both Diazepam administration and CAC produced a memory deficit which was primarily observed in the temporal task, whereas item recognition was spared. These data show that Diazepam and CAC produced similar memory impairments. Thus, our study stressed the potential importance of the GABA/BDZ dysfunction in the production of organic amnesia of alcoholic origin. The overall analysis of the data suggests that both CAC and Diazepam injections would impair forms of memory sustained by automatic or incidental learning.
Re‐establishment of direct synaptic connections between sensory axons and motoneurons after lesions of neonatal opossum CNS (Monodelphis domestica) in culture
Authors: Lepre M. , Fernandéz J. , Nicholls J. G. 
Published: March 2003

AbstractFor functional recovery after spinal cord injury, regenerating fibres need to grow and to reform appropriate connections with their targets. The isolated central nervous system of neonatal opossums aged 1–9 days has been used to analyse the precision with which neurons become reconnected during regeneration. In culture these preparations maintain their electrical activity and show rapid outgrowth through spinal cord crushes or cuts. By recording electrically and by staining with horseradish peroxidase, we first demonstrated that direct reflex connections were already present at birth between sensory fibres in one segment and motoneurons in the same segment and in adjacent segments. As in previous experiments, 5 days after the spinal cord had been crushed, labelled sensory fibres grew across the lesion to reach the next segment (Woodward et al. (1993) J. Exp. Biol., 176, 77–88;Varga et al. (1995a) Eur. J.Neurosci., 7, 2119–2129, Varga et al. (1995b) Proc. Natl. Acad. Sci. USA, 92, 10959–10963). Beyond the lesion the labelled axons abruptly changed direction, traversed the spinal cord and terminated on labelled motoneurons in the ventral horn. In preparations that had regenerated dorsal root stimulation once again initiated ventral root reflexes. Electron micrographs revealed synapses made by labelled sensory axons on motoneurons. Double staining of growing sensory axons and radial glial fibres showed close association, suggesting guidance. These results indicate that the original pathway is re‐established during repair and that appropriate connections are reformed after injury.
Associative and limbic regions of monkey striatum express high levels of dopamine D3 receptors: effects of MPTP and dopamine agonist replacement therapies
Authors: Morissette Marc , Goulet Martin , Grondin Richard , Blanchet Pierre , Bédard Paul J. , Di Paolo Thérèse , Lévesque Daniel 
Published: March 2003

AbstractThe role of the dopamine D3 receptor subtype in the central nervous system is still not well understood. It has a distinct and restricted distribution, mostly associated with limbic territories of the striatum (olfactory tubercle and the shell of nucleus accumbens) in rat brain. Dopaminergic denervation induced by a 6‐hydroxydopamine lesion of the nigrostriatal system in rat down‐regulates the expression of the D3 receptor. In the present study, we investigated the functional neuroanatomy of the dopamine D3 receptor subtype in the monkey (Macaca fascicularis) basal ganglia. We also studied the effect of administration of the dopaminergic neurotoxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) and chronic D1‐like (SKF 82958) or D2‐like (cabergoline) agonist treatments on dopamine D3 receptor levels using receptor autoradiography. Our results clearly show that the distribution of D3 receptors in the monkey is more closely related to associative and limbic components of the striatum (caudate‐putamen), as compared with its sensorimotor counterpart. Hence, D3 receptors may be more specifically involved in cognitive and motivational aspects of striatal functions, which are elaborated in prefrontal, temporal, parietal, cingulate and limbic cortices. Moreover, MPTP administration significantly decreased levels of D3 receptors and this effect was reversed or compensated by a chronic treatment with a D1‐like, but not a D2‐like, receptor agonist. The D3 receptor may represent an important target for adjunct or direct therapy designed to improve cognitive deficits observed in patients with Parkinson's disease, schizophrenia and other illnesses with frontal lobe cognitive disturbances.
Absence of short‐wavelength sensitive cones in the retinae of seals (Carnivora) and African giant rats (Rodentia)
Authors: Peichl Leo , Moutairou Kabirou 
Published: March 2003

AbstractMost non‐primate mammals have two types of cone: short‐wavelength sensitive (S) and middle‐to‐long‐wavelength sensitive (M/L) cones. In two species of African giant rats, Cricetomys gambianus and C. emini, and in two species of earless seals, Phoca hispida and P. vitulina, the retinal cone types and cone distributions were assessed with antibodies specific for the M/L‐cone opsin and the S‐cone opsin, respectively. All four species were found to completely lack S‐cones, while M/L‐cones were present in low densities. M/L‐cone densities, rod densities and cone/rod ratios were determined across the retina. Cone proportions are about 0.3–0.5% in C. gambianus, 0.5–0.8% in C. emini, and 1.5–1.8% in P. hispida. An absence of S‐cones has previously been reported in a few nocturnal mammals. As earless seals are visually active during night and day, we conclude that an absence of S‐cones is not exclusively associated with nocturnality. The functional and comparative aspects are discussed.
Short‐lasting exposure to one odour decreases general reactivity in the olfactory bulb of adult rats
Authors: Buonviso N. , Gervais R. , Chalansonnet M. , Chaput M. 
Published: March 2003

AbstractWe investigated in adult rats whether a relatively short exposure to a novel odour can lead to changes in reactivity of olfactory bulb principal neurons. Naive rats were exposed to isoamyl acetate for 20 min per day either for 6 consecutive days or for a single 20‐min exposure. Control group was non‐exposed. Under anaesthesia, responsiveness of each recorded single mitral/tufted cell was tested towards isoamyl acetate and four other odours. Results show that the proportion of responding cells in the exposed groups decreased drastically when compared to controls. In the two experimental groups recorded 24 h following the last exposure, mitral/tufted cells show a significant decrease in the number of excitatory responses. In parallel, the number of non‐responsive cells increased by at least a fourfold factor. This decrease in reactivity was not selective towards the odour used during the exposure but concerned any of the five test‐odours presented during recordings. Finally, this lower responsiveness was long lasting as it was still observed 10 days after the end of the last exposure. This preliminary study points out the importance of even limited sensory experience in neural representation of odours.
Influence of Gz and Gi2 transducer proteins in the affinity of opioid agonists to μ receptors
Authors: Garzón Javier , Castro Marián , Sánchez‐Blázquez Pilar 
Published: March 2003

AbstractThe affinity displayed by different opioids to μ receptors (ORs) was determined in mouse brain membranes incubated with antibodies directed to Gα subunits of the guanine nucleotide‐binding proteins Gi2 and Gz. Assays were conducted with 10 pm125I‐Tyr27‐β‐endorphin in the presence of 300 nmN,N‐diallyl‐Tyr‐(α‐aminoisobutyric acid)2‐Phe‐Leu‐OH (ICI‐174 864), which prevented the binding of the iodinated neuropeptide to δ‐ORs. Gpp(NH)p or the preincubation of mouse brain membranes with IgGs to Gi2α or Gzα subunits, promoted reductions in the affinity exhibited by the labelled probe. The potencies of β‐endorphin, [D‐Ala2,N‐MePhe4,Gly‐ol5]‐enkephalin (DAMGO) and [D‐Pen2,5]enkephalin (DPDPE) were reduced after impairing the coupling of μ‐ORs to Gi2 or Gz proteins. Morphine showed a loss of affinity towards the μ‐OR after preincubation of membranes with IgGs to Gzα subunits. However, it retained its potency after treatment with the anti‐Gi2α IgGs. Conversely, [D‐Ala2, D‐Leu5]enkephalin (DADLE) and [D‐Ser2, Leu5] enkephalin‐Thr6 (DSLET) showed decreased affinity to μ‐ORs after treatment with anti‐Gi2α IgGs, with no noticeable change following the use of IgGs to Gzα subunits. The affinity exhibited by the opioid antagonists naloxone, naltrexone, naloxonazine and [Cys2,Tyr3,Orn5,Pen7 amide]somatostatin analogue (CTOP) remained unchanged after either treatment. Therefore, the affinity exhibited by opioid agonists of μ‐ORs, but not antagonists, depends on the nature of the G‐protein coupled to these receptors.
Two types of TTX‐resistant and one TTX‐sensitive Na+ channel in rat dorsal root ganglion neurons and their blockade by halothane
Authors: Scholz A. , Appel N. , Vogel W. 
Published: March 2003

AbstractThe clinically employed general anaesthetic halothane was shown to exert action on the peripheral nervous system by suppressing spinal reflexes, but it is still unclear which mechanisms underlie this action. The present study addressed the question whether blockade of tetrodotoxin‐sensitive (TTXs) and ‐resistant (TTXr) Na+‐channels in rat dorsal root ganglia (DRG) neurons by halothane could explain its peripheral effects. Two types of TTXr Na+‐currents, fast and slow, with distinct activation and inactivation kinetics were found in small (< 25 μm) and medium sized (25–40 μm) DRG neurons. These currents were blocked by halothane with IC50 values of 5.4 and 7.4 mmol/L, respectively. Additionally, in a concentration‐dependent manner halothane accelerated the inactivation kinetics of both currents and shifted the inactivation curves to more hyperpolarized potentials. Neither the activation curves of both TTXr Na+‐currents were influenced by halothane nor a voltage‐dependent block at test potentials of the currents was seen. In contrast to that of fast current, the time‐to‐peak for slow current was changed in the presence of halothane. The TTXs Na+‐current which prevailed in large neurons (> 40 μm) was blocked by halothane with an IC50 of 12.1 mmol/L. Its inactivation curve was also shifted to more hyperpolarized potentials and the inactivation kinetics accelerated with increasing halothane concentration. Similarly to TTXr Na+‐currents, the activation curve of TTXs Na+‐current and its time‐to‐peak were not influenced by halothane. It is suggested that two types of TTXr Na+‐currents can explain the heterogeneity in kinetic data for TTXr Na+‐currents. Furthermore, the incomplete blockade of Na+‐currents might underlie the incomplete reduction of spinal reflexes at clinically used concentrations of halothane.
Intracellular Ca2+during metabolic activation of KATPchannels in spontaneously active dorsal vagal neurons in medullary slices
Authors: Ballanyi Klaus , Kulik Anna 
Published: March 2003

AbstractIntracellular Ca2+([Ca2+]i) and membrane properties were measured in fura‐2 dialysed dorsal vagal neurons (DVN) spontaneously active at a frequency of 0.5–5 Hz. [Ca2+]iincreased by about 30 nmupon rising spike frequency by more than 200% due to 20–50 pA current pulses or 10 μmserotonin. It fell by 30 nmupon block of spiking by current‐injection, tetrodotoxin or Ni2+and also during hyperpolarization due to γ‐aminobutyric acid or opening of adenosine triphosphate (ATP) ‐sensitive K+(KATP) channels with diazoxide. KATPchannel‐mediated hyperpolarizations during anoxia or cyanide produced an initial [Ca2+]idecrease which reversed into a secondary Ca2+rise by less than 100 nm. Similar moderate rises of [Ca2+]iwere observed during block of aerobic metabolism under voltage‐clamp as well as in intact cells, loaded with fura‐2 AM. The magnitude of the metabolism‐related [Ca2+]itransients did not correlate with the amplitude of the KATPchannel‐mediated outward current. [Ca2+]idid not change during diazoxide‐induced or spontaneous activation of KATPoutward current observed in 10% of cells after establishing whole‐cell recording. Increasing [Ca2+]iwith cyclopiazonic acid did not activate KATPchannels. [Ca2+]iwas not affected upon block of outward current with sulphonylureas, but these KATPchannel blockers were effective to reverse inhibition of spike discharge and, thus, the initial [Ca2+]ifall upon spontaneous or diazoxide‐, anoxia‐ and cyanide‐induced KATPchannel activation. A sulphonylurea‐sensitive hyperpolarization and [Ca2+]ifall was also revealed in the early phase of iodoacetate‐induced metabolic arrest, whereas after about 20 min, occurrence of a progressive depolarization led to an irreversible rise of [Ca2+]ito more than 1 μm. The results indicate that KATPchannel activity in DVN is not affected by physiological changes of intracellular Ca2+and the lack of a major perturbance of Ca2+homeostasis contributes to their high tolerance to anoxia.
Presynaptic protein interactions in vivo: evidence from botulinum A, C, D and E action at frog neuromuscular junction
Authors: Raciborska Dorota A. , Trimble William S. , Charlton Milton P. 
Published: March 2003

AbstractThe present study examines the paralytic action of botulinum neurotoxins at their natural target, the neuromuscular junction. We asked whether syntaxin, synaptosome‐associated protein of 25 kDa (SNAP‐25) and vesicle‐associated membrane protein (VAMP/synaptobrevin), the proteins proteolysed by botulinum, are susceptible to cleavage in frog nerve terminals, and whether they form complexes in vivo. In control terminals, the three SNAREs were distributed in broad bands at 1 μm intervals, at sites consistent with presynaptic Ca2+ channels. Within 3 h, botulinum A, C, D and E (BoNT/A/C/D/E) blocked nerve‐evoked muscle contractions but their effects on substrate immunoreactivity varied. The effect of BoNT/A on either C‐terminus or N‐terminus immunoreactivity of SNAP‐25 was undetectable after 3‐h incubation, although C‐terminus immunoreactivity was reduced after 24 h; N‐terminus immunoreactivity was not affected even after 36 h. BoNT/E reduced C‐terminus immunoreactivity of SNAP‐25 1.5 h after toxin application when transmitter release was blocked, but required 24 h to reduce N‐terminus immunoreactivity. BoNT/C reduced syntaxin immunoreactivity after 24‐h incubation but did not affect SNAP‐25. BoNT/D reduced VAMP immunoreactivity at 3 h while it increased SNAP‐25 C‐terminal staining fourfold. BoNT/A and BoNT/C applied together for 24 h reduced syntaxin immunoreactivity and that of both C‐ and N‐terminus of SNAP‐25, indicating that retention of SNAP‐25 N‐terminus after cleavage by BoNT/A depended on intact syntaxin. Therefore, we infer that SNAP‐25 interacts with VAMP and with syntaxin in vivo. Neurotoxin action abolished only 40–60% of SNAP‐25, VAMP or syntaxin immunoreactivity suggesting that distinct pools of these proteins, not immediately involved in triggered exocytosis, are resistant to proteolysis.