bluuebunny/crossref_metadata_2025 huggingface dataset:
Significance of the Paralemniscal Tegmental Area for Audio‐motor Control in the Moustached Bat, Pteronotus p. parnellii: The Afferent and Efferent Connections of the Paralemniscal Area
Authors: Schuller G. , Fischer S. , Schweizer H.
Published: April 2006

The paralemniscal tegmental area has been determined in the brain of the New World moustached bat, Pteronotus p. parnellii, by electrical microstimulation eliciting echolocation calls and pinna movements. It is located in the dorsal tegmentum rostral and medial to the dorsal nucleus of the lateral lemniscus and is characterized by medium sized and large neurons. Tracer injections (WGA‐HRP) showed that the most intense input to the paralemniscal tegmental area originates in the intermediate and deep layers of the homolateral superior colliculus. The strong projections from the ipsi‐ and contralateral nucleus praepositus hypoglossus most probably contributes vestibular information. Further inputs in descending order of intensity are from the substantia nigra, the contralateral paralemniscal tegmental area, the putamen, the ventral reticular formation in its lateral portions, the medial cerebellar nucleus and the dorsal reticular formation. Efferent projections of the paralemniscal tegmental area reach the putamen bilaterally, the nucleus accumbens and other parts of the basal ganglia, the pretectal area, the substantia nigra, the intermediate and deep layers of the superior colliculus bilaterally and the tegmental area ventral to it. Connections to the dorsal part of the periaqueductal grey, the cuneiform nucleus and the parabrachial region are important in the context of vocal control, whereas projections to the medial portion of the contralateral facial nucleus may interfere with the control of pinna movement. The findings suggest that the paralemniscal tegmental area is involved in audio‐motor control of vocalization and pinna movements in bats; connectional and functional similarities and disparities to tegmental regions described in other mammals are discussed.
Localization, Differential Expression and Retrograde Axonal Transport Suggest Physiological Role of FGF‐2 in Spinal Autonomic Neurons of the Rat
Authors: Blottner Dieter , Stapf Christian , Meisinger Christof , Grothe Claudia
Published: April 2006

Fibroblast growth factor‐2 (FGF‐2) has marked pharmacological neurotrophic effects on lesioned spinal autonomic neurons following target removal of the adrenal medulla, yet expression and axonal transport in autonomic neurons remain to be shown. We show here FGF‐2 and FGF receptor type 1 (FGFR1) protein and mRNA expression in preganglionic intermediolateral neurons of the rat thoracic spinal cord. While immunoreactivity of both FGF‐2 and FGFR1 co‐localize to intermediolateral neurons, mRNA transcripts of FGFR1, but not of FGF‐2, are detectable in intermediolateral preparations by RNase protection analysis, suggesting protein translocation in viva Unilateral microinjection of 125iodinated FGF‐2 into the adrenal medulla (a major target of intermediolateral neurons) results in significant accumulation of specific radioactivity in thoracic spinal cord tissue, including the intermediolateral neurons, and the ipsilateral splanchnic nerve. Emulsion autoradiography demonstrated labelling over ipsilateral intermediolateral neurons only. Neuronal co‐localization of FGF‐2/FGFR1 protein, differential mRNA expression, specific retrograde axonal transport and the known neurotrophic actions in vivo, strongly suggest unique physiological roles of FGF‐2 in the autonomic nervous system.
Representations of Graphomotor Trajectories in the Human Parietal Cortex: Evidence for Controlled Processing and Automatic Performance
Authors: Seitz Rüdiger J. , Canavan Anthony G. M. , Yágüez Lidia , Herzog Hans , Tellmann Lutz , Knorr Uwe , Huang Yanxiong , Hömberg Volker
Published: April 2006

The aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right‐hand writing in eight right‐handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole‐field visuospatial processing during automatic performance.
Diversity of Potassium Channels Contributing to Differences in Brain Area‐specific Seizure Susceptibility: Sensitivity of Different Potassium Channels to the Epileptogenic Agent Pentylenetetrazol
Authors: Madeja Michael , Musshoff Ulrich , Speckmann Erwin‐Josef
Published: April 2006

The effect of the epileptogenic agent pentylenetetrazol on eight cloned voltage‐operated mammalian potassium channels (expressed in oocytes of Xenopus laevis) was investigated in order to contribute to an explanation for the brain area‐specific differences in seizure susceptibility. Pentylenetetrazol increased the potassium currents at more negative and decreased them at more positive potentials for the channels of the Kvl gene family, whereas for the other channels the currents were decreased over the whole potential range. The sensitivities of the different potassium channels to the epileptogenic agent were different. At a potential of 0 mV, for example, there were strong reductions for the Kvl.1, Kvl.4 and Kv2.1 currents, whereas the decrease was smaller for the Kvl.3 and Kvl.6 currents and was negligible for the Kvl.2, Kvl.5 and Kv3.4 currents. Correlating these data with the distribution patterns of the potassium channels in the hippocampus, the neocortex and the cerebellum (representing examples of brain areas of distinct seizure susceptibility) revealed that in brain areas with higher seizure susceptibility the overall sensitivity of the potassium channels to the epileptogenic agent is augmented. As a whole, the findings give the first evidence that the differences in distributions and properties of potassium channels contribute to differences in the seizure susceptibility of brain areas.
Arm Movement‐related Neurons in the Visual Area V6A of the Macaque Superior Parietal Lobule
Authors: Galletti C. , Fattori P. , Kutz D. F. , Battaglini P. P.
Published: April 2006

Area V6A is a cortical visual area located in the posterior face of the superior parietal lobule in the macaque monkey. It contains visual neurons as well as neurons not activated by any kind of visual stimulation. The aim of this study was to look for possible features able to activate these latter neurons. We tested 70 non‐visual V6A neurons. Forty‐three of them showed an arm movement–related neural discharge due to somatosensory stimulation and/or skeletomotor activity of the upper limbs of the animal. The arm movement‐related neural discharge started before the onset of arm movement, often before the earliest lectromyographic activity. Thus, although the discharge is probably supported by proprioceptive and tactile inputs it is not fully dependent on them. Arm movement‐related neurons of area V6A seem to be well equipped for integrating motor signals related to arm movements with somatosensory signals evoked by those ovements. Taking into account also the visual characteristics of V6A neurons, it seems likely that area V6A as a whole is involved in the visual guiding of reaching
The Synapse Between LE Sensory Neurons and Gill Motoneurons Makes Only a Small Contribution to the Aplysia Gill‐withdrawal Reflex
Authors: Hickie Christopher , Cohen Lawrence B. , Balaban Pavel M.
Published: April 2006

The monosynaptic connection between the mechano‐sensory neurons in the LE cluster and gill motoneurons has been extensively studied and used as a model for the gill‐withdrawal reflex and its behavioural plasticity. In an attempt to evaluate the contribution of this synapse to the behaviour, we used voltage‐sensitive dye recording to determine the number of activated LE neurons and the number of spikes made by each neuron in response to a light touch. In five preparations, light touch activated a median of five sensory cells with a median of 1.6 spikes per cell. From a comparison of the sizes of the motoneuron synaptic potentials elicited by LE spikes and elicited by a light siphon touch, we estimate that the LE sensory neurons contribute ˜5% of the motoneuron synaptic potential in response to this touch. This result casts doubt on the validity of using this synaptic connection as a model for gill‐withdrawal behaviour. Siphon nerve recordings reveal the existence of short‐latency, low‐threshold neurons that may provide much of the sensory input in response to a light touch.
Experience‐dependent Facilitating Effect of Corticosterone on Spatial Memory Formation in the Water Maze
Authors: Sandi Carmen , Loscertales Maria , Guaza Carmen
Published: April 2006

Stress‐related adrenal steroid hormones modulate brain and cognitive function. Electrophysiological studies, including primed burst potentiation and long‐term potentiation, have indicated concentration‐dependent inverted U‐shape effects of corticosterone in hippocampal function and plasticity. Here, we explored the role of corticosterone in the consolidation and long‐term retrieval of spatial learning in the Morris water maze task in rats. We postulated that corticosterone actions might be experience‐dependent with regard to stimulus intensity, such as differential water temperatures. Indeed, rats trained at 19°C showed a quicker rate of acquisition and better long‐term retention than rats trained at 25°C water. In addition, post‐training corticosterone levels, on the first training day, were significantly higher in rats in the 19°C group than in the 25°C group. Performance of rats trained at 25°C, but not at 19°C, water was improved by injecting them i.p. with corticosterone immediately after each training session. Thus, the effect of exogenously administered corticosterone appears to be experience‐dependent, with the experience‐induced corticosterone concentrations as a critical factor determining the cognitive consequences of steroid treatment. Therefore, this work indicates a facilitating corticosterone action, during the post‐training period, on the neural mechanisms determining the strength of information storage under acute, physiological conditions.
Visual Activation in α‐Chloralose‐anaesthetized Cats Does Not Cause Lactate Accumulation in the Visual Cortex as Detected by [1HINMR Difference Spectroscopy
Authors: Kauppinen Risto A. , Eleff Scott M. , Ulatowski John A. , Kraut Michael , Soher Brian , van Zijl Peter C.M.
Published: April 2006

The hypothesis that neuronal activation results in lactate accumulation due to mismatch between glucose and oxygen consumption was tested in the cat model of visual activation by monitoring cerebral metabolism with localized 1H nuclear magnetic resonance spectroscopy (MRS). Adult cats were anaesthetized with α‐chloralose, paralysed and mechanically ventilated. Visual evoked potentials measured over the occipital cortex showed maximal amplitude at 2 Hz stimulation, but the latencies of the early cortical potentials, N1 and P1, were independent of stimulation frequency. High signal‐to‐noise ratio, short echo time volume‐selected [1H]MRS was used to monitor cerebral lactate with a temporal resolution of 70 s. Difference proton spectroscopy unambiguously showed no lactate peak in the visual cortex during visual activation at stimulation frequencies ranging from 1 to 16 Hz. Absence of change in lactate concentration during visual stimulation was confirmed by averaging all the spectra acquired during activation and subtracting them from reference spectra collected in darkness, a procedure that had a calculated lactate detection limit of 0.17 mM. We also reduced the O2 in the inspired air to 13%, which decreased pO2 from 94.5 ± 8.9 to 47.0 ± 6.8 mmHg, during visual stimulation at 2 or 4 Hz. At this low pO2 level, visual stimulation did not cause lactate accumulation in the visual cortex, however. The present data show that neuronal activation to this degree in the cat brain is not associated with aerobic lactate production to an extent that can be detected with 1H MRS.
Molecular and Functional Diversity at Synapses of Individual Neurons In Vitro
Authors: Staple Julie K. , Osen‐Sand Astrid , Benfenati Fabio , Pich Emilio Merlo , Catsicas Stefan
Published: April 2006

We have quantified activity‐dependent uptake of the fluorescent dye FM1–43 in combination with immunocytochemistry for synaptic vesicle‐associated proteins (SVPs) at individual synapses in primary cultures of rat cortical neurons. We show that expression of synaptic proteins is highly variable and that the levels of synaptophysin (p38), synapsin I and sv2, but not synapsin II, correlate with the extent of FM1–43 labelling at synapses. The data indicate that SVP levels affect the uptake of FMI‐43 with different efficacy (p38 > synapsin I > sv2 or synapsin 11). We also found that the relative levels of SVPs vary at individual boutons of single neurons grown in isolation, which indicates that differential regulation of specific SVPs may contribute to the selective modulation of activity at synapses of the same neuron.
Zinc Blocks Acetylcholine Release but not Vesicle Fusion at the Torpedo Nerve–Electroplate Junction
Authors: Parducz Arpad , Corrèges Philippe , Sors Patrick , Dunant Yves
Published: April 2006

The combined effects of Zn2+ treatment and nerve stimulation were studied on cholinergic synapses of the Torpedo rnarmorafa electric organ. Incubation of small pieces of electric tissue in 250 μM ZnCI2 for 2 h irreversibly blocked synaptic transmission by inhibiting the release of acetylcholine. This treatment, however, did not cause any significant fine structural alteration in the nerve‐electroplate junctions. Preparations treated with Zn2+ were submitted to electrical stimulation. In spite of the fact that no transmitter was released, stimulation resulted in the accumulation of calcium in the tissue, and in marked ultrastructural changes. The density of synaptic vesicles was significantly reduced and many of the remaining vesicles were found in close proximity to the presynaptic membrane. Images of vesicles fused with the plasmalemma were abundant, indicating that numerous vesicles were caught in different phases of exocytosis or endocytosis. Freeze‐fracture replicas made from quick‐frozen or chemically fixed material showed a high number of vesicle openings (pits) in the presynaptic plasmalemma. No recovery occurred even after a prolonged period of rest, indicating that retrieval was impaired by zinc treatment. In conclusion, the present experimental paradigm created an unusual situation where fusion of synaptic vesicles to the plasma membrane could be activated independently from the release of transmitter.
Importance of the Different |β Subunits in the Membrane Expression of the α1A and α2 Calcium Channel Subunits: Studies Using a Depolarization‐sensitive α1A Antibody
Authors: Brice N. L. , Berrow N. S. , Campbell V. , Page K. M. , Brickley K. , Tedder I. , Dolphin A. C.
Published: April 2006

The plasma membrane expression of the rat brain calcium channel subunits α1A, α2‐Δ and the β subunits β1b, β2a, β3b and β4 was examined by transient expression in COS‐7 cells. Neither α1A nor α2‐Δ localized to the plasma membrane, either alone or when coexpressed. However, coexpression of α1A or α2‐Δ/α1A with any of the p subunits caused α1A and α2 to be targetted to the plasma membrane. The α1A antibody is directed against an exofacial epitope at the mouth of the pore, which is not exposed unless cells are depolarized, both for native α1A channels in dorsal root ganglion neurons and for α1A expressed with a β subunit. This subsidiary result provides evidence that either channel opening or inactivation causes a conformational change at the mouth of the pore of α1A. Immunostaining for α1A was obtained in depolarized non‐permeabilized cells, indicating correct orientation in the membrane only when it was coexpressed with a subunit. In contrast, β1b and β2a were associated with the plasma membrane when expressed alone. However, this is not a prerequisite to target α1A to the membrane since β3 and β4 alone showed no differential localization, but did direct the translocation of α1A to the plasma membrane, suggesting a chaperone role for the β subunits
Gradation of Kainic Acid‐induced Rat Limbic Seizures and Expression of Hippocampal Heat Shock Protein‐70
Authors: Zhang Xia , Gelowitz Douglas L. , Lai Chien‐Tsai , Boulton Alan A. , Yu Peter H.
Published: April 2006

Systemic injection of kainic acid (KA) induces limbic seizures in rats, which resemble human temporal lobe epilepsy, the most common form of adult human epilepsy. In this study, we have investigated KA‐elicited limbic seizures in the rats by correlating the severity of the seizure attacks with the expression of hippocampal heat shock protein‐70 (HSP70) which has been suggested to be a marker for neuronal injury/death in this model of seizures. After a systemic injection of KA, six stages of limbic seizures have been classified, namely, staring (stage 1), wet dog shake (stage 2), hyperactivity (stage 3), rearing (stage 4), rearing and falling (stage 5), and jumping (stage 6). Stages 4, 5 and 6 were further divided into mild and severe sub‐stages. HSP70 expression was not detected in animals with stages 1 and 2 seizures. At stage 3 a small amount of HSP70 immunoreactive neurons was detected in the CA3 field and the dentate hilus. From stage 4 to stage 5 the degree of HSP70 immunoreactivity increased in the CA1 field from a few positive cells in stage 4 mild to large numbers of immunoreactive neurons in stage 5 severe. HSP70 became detectable in pyramidal cells in the CA2 field from stage 5 severe and higher. In animals with stage 6 seizures, the majority of HSP70 expression became located in glial cells throughout the whole hippocampus. We concluded that HSP70 expression in the hippocampus positively correlates with the severity of KA‐elicited limbic seizures.
Sequential Role of Hippocampus and Amygdala, Entorhinal Cortex and Parietal Cortex in Formation and Retrieval of Memory for Inhibitory Avoidance in Rats
Authors: Izquierdo I. , Quillfeldt J. A. , Zanatta M. S. , Quevedo J. , Schaeffer E. , Schmitz P. K. , Medina J. H.
Published: April 2006

The hippocampus and amygdala, the entorhinal cortex and the parietal cortex participate, in that sequence, both in the formation and in the expression of memory for a step‐down inhibitory avoidance task in rats. Bilateral infusion of AP5 or muscimol caused retrograde amnesia when given O min after training into both hippocampus and amygdala, when given or 180 min after training into the entorhinal cortex, or when given 180 min after training into the parietal cortex. Therefore, memory formation requires the sequential and integrated activity of all these areas mediated by glutamate NMDA receptors in each case. Pre‐test administration of CNQX 1 day after training into hippocampus and amygdala, 1 or 31 days after training in entorhinal cortex, or 1, 31 or 60 days after training in the parietal cortex temporarily blocked retention test performance. Therefore, 1 day after training, all these brain structures are necessary for retrieval; 1 month later, the hippocampus and amygdala are no longer necessary for retrieval but the entorhinal and parietal cortex still are; and 60 days after training only the parietal cortex is needed. In all cases the mechanisms of retrieval require intact glutamate AMPA receptors.
Spontaneous and Repetitive Calcium Transients in C2C12 Mouse Myotubes during In Vitro Myogenesis
Authors: Lorenzon Paola , Giovannelli Aldo , Ragozzino Davide , Eusebi Fabrizio , Ruzzier Fabio
Published: April 2006

Fluorescence videomicroscopy was used to monitor changes in the cytosolic free Ca2+ concentration ([Ca2+]i in the mouse muscle cell line C2C12 during in vitro myogenesis. Three different patterns of changes in [Ca2+]i were observed: (i) [Ca2+]i oscillations; (ii) faster Ca2+ events confined to subcellular regions (localized [Ca2+]i spikes) and (iii) [Ca2+]i spikes detectable in the entire myotube (global [Ca2+]i spikes). [Ca2+]i oscillations and localized [Ca2+]i spikes were detectable following the appearance of caffeine‐sensitivity in differentiating C2C12 cells. Global [Ca2+]i spikes appeared later in the process of myogenesis in cells exhibiting coupling between voltage‐operated Ca2+ channels and ryanodine receptors. In contrast to [Ca2+]i oscillations and localized [Ca2+]i spikes, the global events immediately stopped when cells were perfused either with a Ca2+‐free solution, or a solution with TTX, TEA and verapamil. To explore further the mechanism of the global [Ca2+]i spikes, membrane currents and fluorescence signals were measured simultaneously. These experiments revealed that global [Ca2+]i spikes were correlated with an inward current. Moreover, while the depletion of the Ca2+ stores blocked [Ca2+]i oscillations and localized [Ca2]i spikes, it only reduced the amplitude of global [Ca2+]i spikes. It is suggested that, during the earlier stages of the myogenesis, spontaneous and repetitive [Ca2+]i changes may be based on cytosolic oscillatory mechanisms. The coupling between voltage‐operated Ca2+ channels and ryanodine receptors seems to be the prerequisite for the appearance of global [Ca2+]i spikes triggered by a membrane oscillatory mechanism, which characterizes the later phases of the myogenic process.
Multiple Types of Ca2+ Channels in Mouse Motor Nerve Terminals
Authors: Lin Min‐Jon , Lin‐Shiau Shoei‐Yn
Published: April 2006

We measured neurotransmitter release and motor nerve terminal currents in mouse phrenic nerve‐diaphragm and triangularis sterni preparations, to evaluate the role of Ca2+‐channel subtypes in regulating transmitter release. Saturated concentrations of either ωagatoxin IVA [ω‐Aga‐IVA (0.3 μM), a blocker of P‐type Ca2+channels] or ω‐conotoxin MVIIC [ω‐CTx‐MVIIC (2 μM), a P‐and Q‐type Ca2+‐channel blocker], inhibited nerve‐evoked muscle contractions and the amplitude of endplate potentials respectively. In contrast, combined treatment with nifedipine (50 μM, a blocker of L‐type Ca2+ channels) plus ω‐conotoxin GVIA [ω‐CTx‐GVIA (2 μM), a blocker of N‐type Ca2+ channels] did not elicit inhibitory effects on nerve‐evoked muscle contractions, endplate potentials or nerve terminal waveforms. Because of the non‐linear relationship between endplate potentials and Ca2+ signals, a small decrease in presynaptic Ca2+ entry can significantly reduce the amplitude of the endplate potential. Thus, we applied 3, 4‐diaminopyridine (3, 4‐DAP, a k+‐channel blocker) or high Ca2+(10 mM) to accelerate and amplify the endplate potentials and Ca2+ currents. The endplate potentials amplified by 3, 4‐DAP or by high Ca2+ correspondingly proved to be quite resistant to both ω‐Aga‐IVA and ω‐CTx‐MVIIC; ωAga‐IVA exerted only a partial inhibitory effect on endplate potentials, and the ω‐Aga‐IVA‐resistant component was further inhibited by ω‐CTx‐MVIIC. The component that was resistant to the two toxins could be completely blocked by the non‐selective Ca2+ channel blocker Cd2+ (300 μM). A combination of the two toxins had no significant effects on either spontaneous transmitter release or postsynaptic resting membrane potentials of the diaphragm preparation and the Na+ and K+ waveforms of the triangularis sterni preparations. This finding suggests a preferential inhibitory effect at a presynaptic site. Measuring the Ca2+ currents in the triangularis sterni also revealed partial inhibition by ω‐CTx‐MVIIC with further incomplete inhibition by ω‐Aga‐IVA. Cd2+ (300 μM) abolished the toxin‐resistant component of the Ca2+ current. In contrast, a combination of nifedipine (50 μM) with ω‐CTx‐GVIA (2 μM) was without inhibitory effect. We conclude that multiple types of Ca2+channels, i.e. ω‐Aga‐IVA‐sensitive, ω‐CTx‐MVIIC‐sensitive and toxin‐resistant Ca2+ channels, coexist in mouse motor nerve terminals.
Susceptibility of Cerebellar Granule Neurons Derived from Bcl‐2‐Deficient and Transgenic Mice to Cell Death
Authors: Tanabe Hiroki , Eguchi Yutaka , Kamada Shinji , Martinou Jean‐Claude , Tsujimoto Yoshihide
Published: April 2006

Overproduced Bcl‐2 oncoprotein has been shown to suppress cell death induced by a variety of stimuli in many cell types, including neuronal cells. Because bcl‐2 is expressed in the nervous system where massive cell death is observed during development, endogenous Bcl‐2 is likely to be involved in regulating neuronal cell death. Here we examined the possible role of endogenous Bcl‐2 in the regulation of neuronal cell survival in the central nervous system using primary cultured cerebellar granule neurons from bcl‐2‐deficient, wild‐type and NSE‐bcl‐2‐ transgenic mice. Cerebellar granule neurons from bcl‐2‐deficient mice were more susceptible than those from normal littermates to death induced by reducing the K+ concentration of the medium from high (25 mM) to low (5 mM), and neurons from bcl‐2‐transgenic mice were least susceptible. Similar results were obtained when cell death was induced by serum withdrawal under high K+ conditions or by the presence of etoposide, A23187 or nimodipine. Consistently, bcl‐2 deficiency reduced the number of cerebellar granule neurons per mouse. These results indicate that Bcl‐2 impedes neuronal cell death induced by various stimuli in a dose‐dependent manner, and that endogenous levels of Bcl‐2 are able to regulate neuronal cell survival in the central nervous system.
Expression of GABAA Receptor Subunit mRNAs by Layer V Pyramidal Cells of the Rat Primary Visual Cortex
Authors: Ruano Diego , Perrais David , Rosier Jean , Ropert Nicole
Published: April 2006

The expression of the GABAA receptor subunit mRNAs by layer V pyramidal neurons of the primary visual cortex and cerebellar Purkinje cells was analysed by single‐cell reverse transcription of the mRNAs and amplification of the resulting cDNAs by the polymerase chain reaction. Neurons were identified by infrared Videomicroscopy, and GABAA‐mediated miniature inhibitory postsynaptic currents were recorded. In Purkinje cells, α1, β2, β3, γ2s and γ2L subunit mRNAs were detected within a single cell. In layer V pyramidal cells, a total of ten GABAA receptor subunit mRNAs could be detected, with a mean of seven subunit mRNAs per cell, suggesting GABAA receptor heterogeneity within a single pyramidal cell.
Fluorescent Dye Prelabelled Microglial Cells Migrate into Organotypic Hippocampal Slice Cultures and Ramify
Authors: Hailer Nils P. , Heppner Frank L. , Haas Dorit , Nitsch Robert
Published: April 2006

Microglial cells with their characteristic ramified morphology are exclusively found in healthy CNS tissue, whereas various pathologies are associated with the occurrence of amoeboid, macrophage‐like cells. It is still a matter of discussion whether amoeboid cells are blood‐derived macrophages, or whether a characteristic change in morphology, reflecting activation of previously ramified microglia, takes place. Cells in dissociated microglia culture obtained from healthy rat brains, inevitably developing this amoeboid morphology, were labelled with a fluorescent dye and transferred onto organotypic hippocampal slice cultures. Prelabelled cells with amoeboid morphology invaded these slice cultures and had, after 9 days in vitro, gradually transformed into highly ramified cells. Our findings strengthen the hypothesis that the observed amoeboid and ramified cells belong to a single population of microglia, appearing with different morphologies depending on the presence of stimuli provided by the CNS microenvironment. Microglial cells obviously appear in different shapes and can switch from immunologically resting to activated modes and vice versa.
Different Routes of Ca2+ Influx in NMDA‐Mediated Generation of Nitric Oxide and Arachidonic Acid
Authors: Rodriguez‐Alvarez Jose , Lafon‐Cazal Mireille , Blanco Isaac , Bockaëert Joel
Published: April 2006

Nitric oxide and arachidonic acid act as inter‐ and intracellular messengers in the central nervous system. It is well known that the NMDA‐mediated generation of nitric oxide and arachidonic acid is dependent on extracellular Ca2+. However, the role of voltage‐dependent calcium channels (VDCCs) in this regard is poorly understood. We report here that NMDA‐mediated nitric oxide production in striatal neuron cultures is blocked (80%) by the L‐type VDCC antagonist nifedipine, but not by ω‐conotoxin or ω‐agatoxin IVA, antagonists of the N‐and P‐type VDCCs respectively. By contrast, none of the VDCC antagonists inhibited the NMDA‐mediated release of arachidonic acid. These data indicate that permeation through different Ca2+ channels is responsible for the production of arachidonic acid and nitric oxide in striatal neurons.
A Comparative Study of α2‐ and β‐Adrenoceptor Distribution in Pigeon and Chick Brain
Authors: Femández‐López Arsenio , Revilla Victoria , Candelas Maria Adoración , González‐Gil Joaquin , Diaz Alvaro , Pazos Angel
Published: April 2006

The pharmacological properties and anatomical distribution of α2, β1 and β2‐adrenoceptors in pigeon and chick brains were studied by both homogenate binding and tissue section autoradiography. [3H]Bromoxidine (α2‐adrenoceptor‐), [3H]CGP 12177 (β‐adrenoceptor) and [1251]cyanopindolol (β‐adrenoceptor) were used as radioligands. In both species, [3H]bromoxidine binding to avian brain tissue showed a pharmacological profile similar to that previously reported for α2‐adrenoceptors in mammals. Regarding the anatomical distribution, the areas with the highest densities of α2‐adrenoceptors in the pigeon brain included the hyperstriatum, nuclei septalis, tectum opticum and some brainstem nuclei. Most β‐adrenoceptors found in tissue membranes and sections from chick and pigeon brain were of the β2 subtype, in contrast to what has been reported in the mammalian brain, where the β1 subtype is predominant. A striking difference was found between the two species regarding the densities of these receptors: while pigeon brain was extremely rich in [1251]cyanopindolol binding throughout the brain (mainly cerebellum) in the pigeon, the levels of labelling in the chick brain were much lower; the exception was the cerebellum, which displayed a higher density than other parts of the brain in both species. Overall, our results support the proposed anatomical equivalences between a number of structures in the avian and mammalian encephalon.
Endothelins Promote the Activation of Astrocytes in Rat Neostriatum through ETB Receptors
Authors: Ishikawa Nobue , Takemura Motohide , Koyama Yutaka , Shigenaga Yoshio , Okada Toshikazu , Baba Akemichi
Published: April 2006

The effects of endothelin (ET)‐3 and an ETB receptor agonist on astrocytic activation in rat caudate putamen were examined by an immunohistochemical staining of glial fibrillary acidic protein (GFAP), a marker of reactive astrocytes. A single injection of 40 pmol ET‐3 into rat caudate putamen increased the number of GFAP positive cells compared to that in the contralateral saline‐injected side. Ala1,3,11,15‐ET‐1 (40 pmol), an ETB receptor agonist, also increased the number of striatal GFAP positive cells. The increases in GFAP positive cells were maximum (about 150% of the control side) in 1–2 weeks after injections of the ETs, and then reduced in 4 weeks. A continuous infusion of BQ788, an ETB receptor antagonist (23 nmol/day), into the lateral ventricle of the cerebrum antagonized the effect of Ala1,3,11,15‐ET‐1, while 80788 also reduced the number of GFAP positive cells in saline‐injected caudate putamen. Intrastriatal injection of 40 pmol Ala1,3,11,15‐ET‐1 did not affect the number of cells stained by B4 isolectin from Griffonia simplicifolia, which labels activated microglia/macrophages. Intraperitoneal administration of 5 mg/kg per day chloroquine and 0.2 mg/kg per day colchicine did not affect the action of Ala1,3,11,15‐ET‐1. These results suggest that activation of ETB receptors is involved in the induction of reactive astrocytes.
Excitatory Convergence of Y and Non‐Y Information Channels on Single Neurons in the PMLS Area, a Motion Area of the Cat Visual Cortex
Authors: Wang C. , Dreher B. , Huxlin K. R. , Burke W.
Published: April 2006

We analysed the receptive field properties of neurons in the posteromedial lateral suprasylvian (PMLS) visual cortical area of anaesthetized cats in which there was selective conduction block of the largest (Y‐type) fibres in one optic nerve. As in normal cats, in cats with selective block of one optic nerve the great majority of PMLS cells could be activated by photic stimulation through either eye. However, the responses evoked by stimulation via the eye with the selectively pressure‐blocked optic nerve (‘Y‐blocked eye’) were significantly weaker than those of the same cells evoked by the stimulation via the normal eye. Accordingly, eye dominance histograms were shifted markedly in favour of the normal eye. Furthermore, there was a significant shift towards lower preferred velocities when PMLS cells were photically stimulated via the Y‐blocked eye. Finally, when stimulated via the Y‐blocked eye, PMLS cells responded poorly or not at all to high stimulus velocities (≤100°/s). On the other hand, a number of receptive field properties, such as the spatial organization of receptive fields, the size of the discharge fields, orientation tuning and direction selectivity indices, were not significantly affected by the removal of the Y input. We conclude that virtually all neurons in the PMLS area of the cat receive excitatory input from both Y and non‐Y information channels, although the Y channel provides the dominant input and makes the principal contribution to the detection of high‐velocity motion.
Up‐regulation of Cyclooxygenase‐2 Expression in Cultured Microglia by Prostaglandin E2, Cyclic AMP and Non‐steroidal Anti‐inflammatory Drugs
Authors: Minghetti Luisa , Polazzi Elisabetta , Nicolini Alessia , Créminon Christophe , Levi Giulio
Published: April 2006

Cyclooxygenase‐2, the inducible isoform of cyclooxygenase, is highly expressed in microglial cells activated by bacterial lipopolysaccharide and is a major regulatory factor in the synthesis of prostanoids, such as prostaglandins, prostacyclin and thromboxanes. Since prostanoids are potent modulators of inflammation, immune responses and neurotoxicity, the regulation of their synthesis may be crucial for balancing microglial neuroprotective and neurotoxic activities. The present study shows that expression of cyclooxygenase–2 and prostanoid production in cultured rat microglia activated by lipopolysaccharide is up‐regulated by cyclic AMP (CAMP), as indicated by experiments performed in the presence of adenylyl cyclase activators, cAMP analogues and protein kinase A‐specific inhibitors. Exogenous prostaglandin E2 (PGE2), which elevates the cAMP level in microglial cells, also increased the lipopolysaccharide‐induced expression of cyclooxygenase–2 and production of thromboxane in a dose– and time‐dependent manner. The observations that the lipopolysaccharide‐induced prostanoid production was specifically increased by 11‐deoxy‐16,16‐dm PGE2, a selective agonist at the PGE2 receptor EP2 coupled to the activation of adenylyl cyclase, and that the enhancing effect of PGE2 was partially prevented by specific inhibitors of adenylyl cyclase and protein kinase A, suggest that the up‐regulation of cyclooxygenase–2 expression by PGE2 is mediated by CAMP, through a putative microglial EP2 receptor. Unexpectedly, non‐steroidal anti‐inflammatory drugs such as indomethacin and 6–methoxy naphthalene acetic acidic, which inhibit cyclooxygenase enzymatic activity and abrogate prostanoid synthesis, caused a moderate but consistent up‐regulation of cyclooxygenase–2 expression. In conclusion, while the strong up‐regulation of cyclooxygenase–2 expression by exogenous PGE2 appears to be mediated by EP2 receptors and CAMP, the limited down‐regulation caused by anti‐inflammatory drug treatments may be either due to arachidonic acid metabolites other than PGE2, or to PGE2 itself, acting through a distinct CAMP‐independent signalling pathway.
Selectivity of Macaque MT/V5 Neurons for Surface Orientation in Depth Specified by Motion
Authors: Xiao D.‐K. , Marcar V. L. , Raiguel S. E. , Orban G. A.
Published: April 2006

Area MT/V5 in the macaque brain is one of the major cortical regions involved in the analysis of retinal image motion. The majority of the neurons in this cortical area have non‐uniform antagonistic surrounds as components of their receptive field complexes. Theoretical studies indicate that such asymmetrical surrounds should enable neurons to extract orientation in depth from motion. Here we show that nearly half of the MT/V5 neurons encode the tilt component of the orientation in depth of a plane specified by motion. Furthermore, we show that such selectivity for depth from motion depends on the presence of an asymmetrical surround and on the speed tuning of those asymmetrical surround influences.
Differential Expression of Syntrophins and Analysis of Alternatively Spliced Dystrophin Transcripts in the Mouse Brain
Authors: Górecki Dariusz C. , Lukasiuk Katarzyna , Barnard Eric A. , Abdulrazzak Hassan
Published: April 2006

Expression of syntrophin genes, encoding members of the dystrophin‐associated protein complex, was studied in the mouse brain. In the hippocampal formation there is distinctive co‐localization of specific syntrophins with certain dystrophin isoforms in neurons, e.g. α1,‐syntrophin with the C‐dystrophin in CA regions and β2‐syntrophin with the G‐dystrophin in the dentate gyrus. Expression of the al‐syntrophin is predominant in CA regions and the olfactory bulb and it is also present in the cerebral cortex and the dentate gyrus. The β2‐syntrophin mRNA is most abundant in the dentate gyrus and is also evident in the pituitary, the cerebral cortex and in Ammon's horn and in traces in the caudate putamen. The choroid plexus was labelled by both α1 and β2‐syntrophin‐specific probes. The expression of syntrophins in the brain correlates with expression of dystrophins and dystroglycan. There are brain areas such as the cerebral cortex where several different syntrophins and dystrophins are expressed together. Syntrophin expression co‐localizes with utrophin in the choroid plexus and caudate putamen. Finally, no syntrophin was detected in the cerebellar Purkinje cells where the specific dystrophin isoform (P‐type) is present. This specific distribution of syntrophins in the brain is particularly interesting, as muscle syntrophin interacts with neuronal nitric oxide synthase. This may suggest that the dystrophin‐associated protein complex may be involved in synaptic organisation and signal transduction machinery in both muscle and neurons. The dystrophin isoform, with exons 71–74 spliced out and hence lacking syntrophin binding sites, had been believed to be predominant in the brain, but our analyses using in situ hybridization, S1 nuclease protection and the semi‐quantitative polymerase chain reaction revealed that this alternatively spliced mRNA is a minor, low abundance form in the brain.
Neurite Outgrowth Inhibitor of Gliotic Brain Tissue. Mode of Action and Cellular Localization, Studied with Specific Monoclonal Antibodies
Authors: Bovolental Paola , Fernaud‐Espinosa Isabel , Mendez‐Otero Rosalia , Nieto‐Sampedro Manuel
Published: April 2006

Membranes from injured adult rat brain express a heparan/chondroitin sulphate proteoglycan that inhibits neurite outgrowth in vitro. We have developed monoclonal antibodies (Mabs) against this proteoglycan, two of which were characterized and used for the study of the inhibitor mode of action and localization in normal and injured adult brain. The antibodies recognized a molecule of apparent molecular weight 200 kDa in Western blots of injured brain membranes. One of the Mabs blocked both the inhibition of neurite outgrowth and the growth cone collapse activity, associated with the proteoglycan. In adult brain, inhibitor immunoreactivity was found predominantly in neurons but, after a lesion, it was associated mainly with reactive glial cells. The localization of neurite outgrowth inhibitors in reactive glia supports the idea that gliotic tissue is largely responsible for the failure of axonal regeneration in mammalian CNS
Synchronization of Neuronal Activity Promotes Survival of Individual Rat Neocortical Neurons in Early Development
Authors: Voigt Thomas , Baier Herwig , de Lima Ana Dolabela
Published: April 2006

Neural activity is thought to play a significant role during the development of the cerebral cortex. In this study, we examined the effects of global activity block or enhancement and the effects of patterned firing on the ability of cultured rat neocortical neurons to survive during the second week in vitro, beyond the beginning of synaptogenesis. Blockade of neuronal activity by adding tetrodotoxin (TTX) and increasing magnesium concentration in the medium strongly reduced the survival of cortical cells. Increasing neuronal activity by raising the external potassium concentration significantly improved the survival of cortical neurons. We postulated that in a developing neuronal network the survival of nerve cells is regulated by synaptically mediated events that involve changes in the intracellular calcium concentration. To examine this question further, we monitored the activity of the developing network by optically recording the intracellular calcium signals of many neurons simultaneously. These recordings show that in low magnesium neocortical neurons express synchronized oscillation of their intracellular calcium concentration. The ability of a network to synchronize the changes in intracellular calcium of multiple cells appeared gradually during the second week in culture, paralleled by both an increase in the synaptic density and a decline in the number of surviving neurons. By examining the fate of identified cells several days after a recording session, we found that those nerve cells that were co‐activated with other neurons had a significantly higher chance to survive than cells that did not participate in synchronized events. These experiments demonstrate that during early cortical network development cortical neurons show synchronized firing activity and that the survival of neurons is at least partially dependent on this pattern of neuronal activity.
Selective Upregulation of Cytokine Receptor Subchain and Their Intracellular Signalling Molecules After Peripheral Nerve Injury
Authors: Yao Gui Lan , Kato Hidemasa , Khalil Mansur , Kiryu Sumiko , Kiyama Hiroshi
Published: April 2006

Numerous studies have suggested that growth factors and cytokines play an important role in the survival of injured neurons and in neurite elongation. Therefore, intracellular signalling pathways activated by growth factors and cytokine receptors play an important role in neuronal survival or for the re‐establishment of connection. Since the JAK (janus kinase)‐STAT (signal transducers and activators of transcription) signal transduction pathway is known to play a major role in cytokine receptor signalling, we first examined regulation of JAK gene expression following peripheral nerve injury by in situ hybridization histochemistry. The rat hypoglossal nerve was axotomized unilaterally and the mRNA levels for JAKI, JAK2. JAK3 and TYK2 were examined in the hypoglossal nucleus at postoperative times ranging from 1 to 35 days. Among the JAK family members, JAK2 and JAK3 were substantially increased in injured hypoglossal motoneurons, whereas no significant increases were observed for JAK1 and TYK2. These changes were further confirmed by immunohistochemistry using antibodies specific to JAKP and JAK3. In addition, we examined the JAK2 and JAK3 associated cytokine receptor components, IL‐2R y and gp130, which are common to various cytokine receptors. Among these, gp130 immunostaining was upregulated after nerve injury. This was also confirmed by in situ hybridization. These results suggest that the injured neuron prepares the molecular machinery involved in certain cytokine receptor signalling pathways at an early phase of the regenerative process, accelerating for the neuron to respond to cytokines that may regulate survival and/or neurite elongation.
Reelin mRNA Expression During Mouse Brain Development
Authors: Schiffmann S. N. , Bernier B. , Goffinet A. M.
Published: April 2006

Using in situ hybridization, expression of the mRNA for reelin, the gene most probably responsible for the reeler trait, was studied during mouse brain development. from embryonic day 13 to maturity. The highest level of expression was found in Cajal‐Retzius neurons, while a high signal was also seen in the olfactory bulb, the external granular layer of the cerebellum and, particularly at early developmental stages, in hypothalamic differentiation fields, tectum and spinal cord. A moderate to low level of expression was found in the septa1 area, striatal fields, habenular nuclei, some thalamic nuclei, particularly the lateral geniculate, the retina and some nuclei of the reticular formation in the central field of the medulla. Paradoxically, no reelin expression was detected in radial glial cells, the cortical plate, Purkinje cells, inferior olivary neurons and many other areas that are characteristically abnormal in reeler mutant mice. Together with other preliminary studies, the present observations suggest that the action of reelin is indirect, possibly mediated by the extracellular matrix. Most of the data can be explained by supposing that reelin is a cell‐repulsive molecule which prevents migrating neurons from invading reelin‐rich areas, and thus facilitates the deployment of radial glial cell processes and the formation of early architectonic patterns.
Dopaminergic Neurons in the Rat Retina Express Dopamine D2/3 Receptors
Authors: Veruki Margaret L.
Published: April 2006

The localization of dopamine D2 and D3 receptors in the rat retina was studied using a polyclonal antibody raised against a peptide sequence common to the dopamine D2 and D3 receptors (D2/3). The D2/3 receptor antibody labelled a small number of somata in the innermost part of the inner nuclear layer and in the ganglion cell layer and a small number of photoreceptor outer segments. Processes in both plexiform layers were also labelled. Double‐labelling experiments with the antibody against the D2/3 receptor and an antibody against tyrosine hydroxylase to label dopaminergic neurons resulted in the co‐localization of the two antibodies. This demonstrates directly that dopaminergic neurons in the retina express D2/3 receptors. As previous biochemical and physiological studies have demonstrated that activation of D2–like receptors inhibits the release of dopamine in the retina, the present results suggest that the D2/3 receptors on dopaminergic neurons function as autoreceptors.