bluuebunny/crossref_metadata_2025 huggingface dataset:
Memory Impairments Following Lesions to the Mammillary Region of the Rat
Authors: Sziklas Viviane , Petrides Michael
Published: April 2006

The contribution of the mammillary region to learning and memory was investigated. It was demonstrated that lesions of this region impair performance on tasks that require memory for spatial information but that the deficit depends both on the amount of damage within the region and the difficulty of the task. A dissociation in the effect of such lesions on performance of comparable spatial and non‐spatial memory tasks was shown. In contrast to the deficits observed on spatial memory tasks, the acquisition and retention of a complex non‐spatial memory task was not impaired after extensive damage to the mammillary region. Such lesions also did not impair performance in a conditioned taste aversion task. These experiments suggest that the mammillary region may be selectively involved in spatial learning and memory.
Pharmacological and Immunohistochemical Evidence for Serotonergic Modulation of Cholinergic Nucleus Basalis Neurons
Authors: Khateb A. , Fort P. , Alonso A. , Jones B. E. , Mülethaler M.
Published: April 2006

Identified electrophysiologically by low threshold bursts and transient outward rectification, cholinergic nucleus basalis neurons were recorded and labelled intracellularly in guinea‐pig basal forebrain slices. By means of a triple labelling immunofluorescent technique, serotonin‐immunoreactive fibres were visualized in close proximity to the soma and dendrites of the biocytin‐labelled, choline acetyl transferase (ChAT)‐immunoreactive cells. By bath application, 5‐hydroxytryptamine (5‐HT) produced a direct hyperpolarization of the identified cells which was mimicked by 5‐HT1A receptor agonists, suggesting that it may inhibit the tonic firing but also modulate the low threshold bursting of the cholinergic nucleus basalis neurons.
Sarcoplasmic Calcium‐binding Proteins in Aplysia Nerve and Muscle Cells
Authors: Pauls T. L. , Cox J. A. , Heizmann C. W. , Hermann A.
Published: April 2006

Muscle (body wall, buccal mass, heart) and neural tissue of the marine mollusc Aplysia californica was analysed for calcium‐binding proteins using transblot45Ca overlay, Western blotting and two‐dimensional polyacrylamide gel electrophoresis, and several low molecular weight calcium‐binding proteins were identified. Our results show that Aplysia muscle contains an abundant protein with a Mr of ∼20 000 with strong 45Ca2+‐binding ability and cross‐reactivity to antibodies against the sarcoplasmic calcium‐binding protein isoform II (SCP II) from Amphioxus. Immunocytochemical studies revealed that isoforms of SCP are distributed in a tissue‐specific manner, SCP II‐like protein is exclusively present in muscle fibres closely associated with the contractile machinery, whereas the isoform I (SCP I‐like protein) is exclusively present in a subset of neurons, suggesting a function in their calcium regulation. In addition, a novel 45Ca2+‐binding protein of Mr 43 000, pl 4.7, was found in muscle and in neurons. A third protein of Mr 40 000, pl 4.8, cross‐reacts with anti‐parvalbumin and anti‐calbindin D‐28K antibodies.
Characterization of a Calcium‐dependent Current Generating a Slow Afterdepolarization of CA3 Pyramidal Cells in Rat Hippocampal Slice Cultures
Authors: Caeser Manfred , Brown David A. , Gähwiler Beat H. , Knöpfel Thomas
Published: April 2006

A depolarization‐induced, slowly decaying inward current was examined in slice‐cultured CA3 pyramidal cells by voltage‐clamp techniques and microfluorometric measurements of cytosolic free Ca2+ concentration ([Ca2+]i). Action potentials elicited by intracellular injection of short‐lasting (50 – 100 ms) depolarizing current pulses were followed by a slowly decaying afterhyperpolarization (AHP). After switching to voltage‐clamp mode, short‐lasting (50 – 100 ms) depolarizing voltage jumps from –60 mV to between –30 and 0 mV induced a slowly decaying outward aftercurrent (IAHP) which was depressed by bath application of muscarine (0.5 μM). In the presence of muscarine, the same depolarizations induced a slowly decaying afterdepolarization (ADP) or inward aftercurrent (IADP)in voltage‐clamp mode. This current was also induced in the presence of trans(±)‐1‐aminc‐1,3‐cyclopenta‐nedicarboxylic acid (t‐ACPD, 5 μM), an agonist of metabotropic glutamate receptors, but not in the presence of noradrenalin (5 μM), while both of these agonists depressed IAHP. IADP was depressed by reducing the external Ca2+ concentration from 3.8 to 0.5 mM, by external Co2+ (1 mM) and by external Cd2+ (10 – 100 μM). Combined voltage‐clamp recordings and microfluorometric measurements of [Ca2+]i using the Ca2+ indicator fura‐2 revealed that the amplitude of IADP was correlated with the amplitude of depolarization‐induced Ca2+ influx, IADP was absent at membrane potentials < –90 mV, and reached maximal amplitudes at ∼–55 mV. Raising the extracellular K+ concentration from 2.7 to 13.5 mM increased the amplitude of IADP and resulted in a positively directed shift of the apparent reversal potential of IADP. When the external Na+ concentration was reduced from 157 to 33 or 18 mM the current reversed at more negative potentials and was reduced to 40 and 21%, respectively, of control amplitude. Lowering the external Cl‐ concentration from 159 to 20 mM did not affect IADP. We conclude that IADP most likely represents a Ca2+‐activated cation current, rather than a Ca2+ tail current, or an electrogenic Ca2+ extrusion current.
Activity‐dependent Refinement of Inhibitory Connections
Authors: Sanes Dan H. , Takács Catherine
Published: April 2006

Several lines of evidence suggest that excitatory synaptic transmission contributes to the maturation of precise neuronal connections. In the present study we determined whether the specific innervation pattern of single inhibitory arborizations was dependent upon neuronal activity during development. A homogeneous group of glycinergic inhibitory neurons in the central auditory system, the medial nucleus of the trapezoid body (MNTB), was functionally denervated in neonatal gerbils. The anatomical specificity of single MNTB terminal arborizations was subsequently measured along the tonotopic axis of a postsynaptic target, the lateral superior olive. Here we demonstrate that inhibitory terminal boutons spread a significantly greater distance along the frequency axis of the postsynaptic target following functional denervation. Although total arbor length remained unchanged, there was a significant increase in the number of branch points, suggesting de novo sprouting. The results indicate that normal inhibitory synaptic activity contributes to the developmental refinement of specific neuronal connections.
Phosphoproteins of Cultured Cerebellar Granule Cells and Response to the Differentiation‐promoting Stimuli NMDA, High K+ and Ionomycin
Authors: Graham Margaret E. , Burgoyne Robert D.
Published: April 2006

In order to investigate signalling pathways involved in the control of granule cell differentiation, survival and other functions by depolarization or activation of NMDA receptors we have characterized protein phosphorylation in cerebellar granule cells. Cultures of cerebellar granule cells were incubated with 32P orthophosphate and then challenged with NMDA, K+ or the Ca2+ ionophore ionomycin, agents which raise [Ca2+]i and stimulate differentiation and survival. Upon separation of labelled phosphoproteins by two‐dimensional gel electrophoresis three differences were found in response to all of these agents. These were an increase in acidity of two phosphoproteins of 87 and 48 kDa (p87 and p48) and increased 32P‐incorporation into a phosphoprotein of 120 kDa (p120). Treatment with PMA which stimulates neurite outgrowth but not survival affected p87 (increased its acidity) but not p48. The acidic shift of p87, therefore, is not sufficient to stimulate granule cell survival. The identification of p87 as the actin‐binding MARCKS protein and the demonstration of its presence in neurites and growth cones of granule cells suggests that it may be involved in NMDA‐stimulated neurite outgrowth. The phosphoproteins p120 and p48 may potentially be involved in events linking the rise in [Ca2+]i to increased granule cell survival or other aspects of granule cell differentiation.
Negative Regulation of Schwann Cell Myelin Protein Gene Expression by the Dorsal Root Ganglionic Microenvironment
Authors: Cameron‐Curry Patrizia , Dulac Catherine , Le Douarin Nicole M.
Published: April 2006

In vivo, the surface glycoprotein Schwann cell myelin protein (SMP) is expressed in the quail peripheral nervous system exclusively by Schwann cells. It is not detectable at any developmental stage either in enteric glia or in ganglionic satellite cells. We demonstrate here that the satellite glial cells of the dorsal root ganglia start to express SMP on their surface when they are dissociated into single cells and cultivated in vitro. Activation of SMP synthesis is a rapid event observed in mass cultures of dorsal root ganglia dissociated cells as soon as 4 h after the onset of the culture. Confocal microscope analysis revealed that satellite cells may acquire the Schwann cell marker when still in close contact with the neuronal soma. Clonal cultures of satellite cells from E8 dorsal root ganglia demonstrated that the progeny of these SMP‐negative cells steadily express SMP. This, together with similar results previously obtained with enteric glia, suggests that the SMP‐positive phenotype is a constitutive trait of the peripheral glial cell lineage which is inhibited in satellite cells in vivo by the microenvironment prevailing in the peripheral nervous system ganglia.
Widespread and Developmentally Regulated Expression of Neurotrophin‐4 mRNA in Rat Brain and Peripheral Tissues
Authors: Timmusk Tõnis , Belluardo Natale , Metsis Madis , Persson Håkan
Published: April 2006

The neurotrophin gene family includes four structurally related proteins with neurotrophic activities. Two of them, nerve growth factor and brain‐derived neurotrophic factor (BDNF), have been studied in detail and information has recently emerged on the expression and function of the third member, neurotrophin‐3. In contrast, little information is available on neurotrophin‐4 (NT‐4), the most recently isolated member of this family. In this report we have used a sensitive RNAase protection assay to analyse the developmental expression of NT‐4 mRNA in the rat brain and in 12 different rat peripheral organs. In heart, liver and muscle plus skin NT‐4 mRNA levels were maximal at embryonic day (E) E13 (the earliest time point tested), with reduced levels at later times of development. In lung, kidney and thymus similar levels were seen from E13 to postnatal day (P) 1, with reduced levels in the adult. In testis, ovary and salivary gland NT‐4 mRNA was detected at E16 with a peak shortly after birth. During brain development, NT‐4 mRNA was maximal at E13 followed by a decrease around birth, after which the level increased. The postnatal increase of NT‐4 mRNA was also seen in cerebral cortex and brain stem analysed separately, while in the hippocampus similar levels were found from P1 to adulthood. NT‐4 mRNA was detected in all ten adult rat brain regions analysed with only small regional variations, being highest in pons–medulla, hypothalamus, thalamus and cerebellum. Adult rat thymus, thyroid, muscle, lung and ovary contained higher levels of NT‐4 mRNA than brain, while all other adult tissues showed similar or lower levels than in the brain. The highest level of NT‐4 mRNA overall was found in P1 testis. For comparison, BDNF mRNA was analysed in the same tissues. The expression of BDNF mRNA was in many cases different from that of NT‐4 mRNA. The peak of NT‐4 mRNA expression in several of the peripheral tissues coincided with the peak of naturally occurring neuronal cell death in peripheral ganglia. This is consistent with the possibility that NT‐4 acts as a target‐derived trophic factor in vivo. The widespread and increased expression of NT‐4 mRNA during postnatal brain development could reflect a trophic role of NT‐4 for central nervous system neurons. However, non‐neuronal functions of NT‐4 are also possible, particularly in male and female reproductive tissues, where the NT‐4 protein could function as a growth factor for immature germ cells.
An Abundant mRNA of the Embryonic Brain Persists at a High Level in Cerebellum, Hippocampus and Olfactory Bulb During Adulthood
Authors: Studler Jeanne‐Marie , Glowinski Jacques , Lévi‐Strauss Matthieu
Published: April 2006

In order to identify markers of the two neuronal populations which are successively involved in forebrain ontogenesis, we performed a differential screening of a murine cDNA library with two radiolabelled probes corresponding to striatal mRNAs extracted at embryonic day (E) 17 and E20, i.e. before and after the invasion of the striatum by the late‐born matrix neurons. One of the selected clones, the 3.1 cDNA, corresponds to a very abundant embryonic neuronal transcript enriched in the germinal zones at E17 and in superficial cortical layers and striatum at E20, suggesting that it is expressed mainly in neurons belonging to a late migration wave. During adulthood, it persists at a high level in the granular layer of the cerebellum, the hippocampus and the olfactory bulb, which are the sites of postnatal neurogenesis and intense synaptic plasticity. This 2000 base RNA is enriched in polysomal fractions and encodes a small putative 68 amino acid polypeptide which is conserved in mouse and man.
Urokinase‐type Plasminogen Activator Expression by Neurons and Oligodendrocytes During Process Outgrowth in Developing Rat Brain
Authors: Dent M. A. R. , Sumi Y. , Morris R. J. , Seeley P. J.
Published: April 2006

The expression of tissue‐ and urokinase‐type plasminogen activators has been studied in developing cerebellum, hippocampus, cerebral cortex, olfactory bulb and olfactory mucosa of the rat by in situ hybridization. All identifiable neurons express urokinase mRNA from an early stage in their development, and this expression appears to coincide with the onset of axogenesis. For cerebellar granule cells, both axonal growth and urokinase expression are initiated before they migrate from the external granule layer; for the majority of neocortical neurons, however, both processes are commenced after the cells have migrated to the cortical plate. Neurons continue to express this protease in the adult. The large projection neurons exhibit the highest levels of message, the smaller interneurons having much lower levels except for hippocampal granule cells, which have notably high levels of expression. Glial cells generally do not express urokinase message, except for transient expression by oligodendrocytes in developing fibre tracts during the period of myelination. Thus for both neurons and oligodendrocytes, the onset of urokinase‐type plasminogen activator expression coincides with their initiation of major process outgrowth, although neurons maintain this expression in the adult, possibly to retain a degree of synaptic plasticity. In contrast, although high levels of message for the related protease, tissue plasminogen activator, are found in the embryonic floor plate, in postnatal brain it is abundantly expressed only by ventricular ependymal cells and by cells in connective tissue surrounding the olfactory nerve.
Spatiotemporal Distribution of Ca2+ Following Axotomy and Throughout the Recovery Process of Cultured Aplysia Neurons
Authors: Ziv Noam E. , Spira Micha E.
Published: April 2006

This study investigates the alterations in the spatiotemporal distribution pattern of the free intracellular Ca2+ concentration ([Ca2+]i) during axotomy and throughout the recovery process of cultured Aplysia neurons, and correlates these alterations with changes in the neurons input resistance and trans‐membrane potential. For the experiments, the axons were transected while imaging the changes in [Ca2+]i with fura‐2, and monitoring the neurons’resting potential and input resistance (Ri) with an intracellular microelectrode inserted into the cell body. The alterations in the spatiotemporal distribution pattern of [Ca2+]i were essentially the same in the proximal and the distal segments, and occurred in two distinct steps: concomitantly with the rupturing of the axolemma, as evidenced by membrane depolarization and a decrease in the input resistance, [Ca2+]i increased from resting levels of 0.05 – 0.1 μM to 1 – 1.5 μM along the entire axon. This is followed by a slower process in which a [Ca2+]i front propagates at a rate of 11 – 16 μm/s from the point of transection towards the intact ends, elevating [Ca2+]i to 3 – 18 μM. Following the resealing of the cut end 0.5 – 2 min post‐axotomy, [Ca2+]i recovers in a typical pattern of a retreating front, travelling from the intact ends towards the cut regions. The [Ca2+]i recovers to the control level 7 – 10 min post‐axotomy. In Ca2+‐free artificial sea water (2.5 mM EGTA) axotomy does not lead to increased [Ca2+]i and a membrane seal is not formed over the cut end. Upon reperfusion with normal artificial sea water, [Ca2+]i is elevated at the tip of the cut axon and a membrane seal is formed. This experiment, together with the observations that injections of Ca2+, Mg2+ and Na+ into intact axons do not induce the release of Ca2+ from intracellular stores, indicates that Ca2+ influx through voltage gated Ca2+ channels and through the cut end are the primary sources of [Ca2+]i following axotomy. However, examination of the spatiotemporal distribution pattern of [Ca2+]i following axotomy and during the recovery process indicates that diffusion is not the dominating process in shaping the [Ca2+]i gradients. Other Ca2+ regulatory mechanisms seem to be very effective in limiting these gradients, thus enabling the neuron to survive the injury.
Functional Consequences of a Single Nerve Growth Factor Administration Following Septal Damage in Rats
Authors: Pallage Viviane , Knusel Beat , Hefti Franz , Will Bruno
Published: April 2006

This study examined how possible nerve growth factor (NGF)‐induced behaviour changes after septal damage might be modulated by the lesion extent, the dose of NGF administered and the delay between surgery and the onset of testing. In a first experiment, young rats which received electrolytic septal lesions of high or low intensity (inducing respectively large and mild lesions) were treated with 10 or 30 μg NGF administered intrahippocampally in a single injection. They were tested 4 months postoperatively for open field ambulation, spontaneous alternation and radial maze performance. It was observed that irrespective of the severity of the lesions rats were impaired in the spontaneous alternation and radial maze tests; however, no obvious changes appeared in the open field test. While an NGF injection did not affect behavioural performances in rats with large lesions, it was capable of ameliorating behavioural deficits in the spontaneous alternation and radial maze tests of rats with mild lesions in both NGF dosage groups. It was also seen that lesions produced a general decrease in hippocampal choline acetyltransferase (ChAT) activity, which was not significantly affected by an NGF administration. There was no significant correlation between ChAT activity and behavioural performance of NGF‐treated rats. In a second experiment, young rats received mild septal lesions and were treated with 10 μg NGF. These rats were tested 2 weeks postoperatively for radial maze performance. NGF rats exhibited similar behaviour to controls with regard to all of the variables measured. The present results suggest that a single NGF administration spares some abilities to use spatial information efficiently providing lesions are partial.
Recovery of Brightness Discrimination in Adult Rats despite Progressive Loss of Retrogradely Labelled Retinal Ganglion Cells after Controlled Optic Nerve Crush
Authors: Sautter Jürgen , Sabel Bernhard A.
Published: April 2006

Restoration of brightness discrimination was studied in adult rats after controlled crush of the optic nerve in order to further characterize a recently introduced experimental brain injury model. Mild, moderate or severe crush of the optic nerve produced partial or complete loss of the ability to perform a brightness discrimination task. Two to three weeks following mild injury we observed nearly complete spontaneous behavioural recovery whereas recovery was more limited after moderate and totally absent after severe crush. Horseradish peroxidase (HRP) injected into the superior colliculus was transported retrogradely across the lesion site and accumulated in retinal ganglion cells (RGCs). Two days following mild, moderate or severe crush, 28, 23 and 8% respectively of RGCs were found to be labelled with HRP, indicating that they are still connected with their target and are therefore presumably intact. RGC loss affected all areas of the retina homogeneously. At postoperative day 14, the number of morphologically‘intact’RGCs declined even further to 11% in the mild injury group, despite our observation of recovery of vision to near‐normal levels. The mechanism whereby such impressive neuronal plasticity is achieved despite the rather small number of intact RGCs is still unknown. However, further studies of the crush model using additional behavioural, morphological and electrophysiological techniques may allow us to determine more clearly the biological basis of recovery of function after central nervous system injury.
The Mode of Activation of a Barrel Column: Response Properties of Single Units in the Somatosensory Cortex of the Mouse upon Whisker Deflection
Authors: Welker E. , Armstrong‐James M. , Van der Loos H. , Kraftsik R.
Published: April 2006

Response properties of single units in the mouse barrel cortex were studied to determine the sequence in which the neurons that form a cortical column become activated by a single‘natural’stimulus. Mice (n= 11) were anaesthetized with urethane. For a total of 153 cells, grouped by cortical layer, responses to a standardized deflection of a single whisker were characterized using poststimulus time and latency histograms. Usually, for each unit, data were collected for stimulation of its principal whisker (PW; the whiskers corresponding to the barrel column in which the cell was located) and of the four whiskers surrounding the PW. In all layers, PW stimulation evoked responses at shorter latency than surround whisker stimulation. In layers II – III and IV a bimodal distribution of cells according to latency to PW stimulation was found. Statistical analysis indicated the presence of two classes of cells in each of these layers:‘fast’units (latency < 15 ms) and 'slow’units (latency >15 ms). The great majority of cells in layers I, V and VI fired at latencies of >20 ms to PW stimulation. In general, stimulation of surround whiskers evoked a smaller response than PW stimulation. The fast cells of layer IV showed the greatest response to PW stimulation (mean = 1.78 spikes/100 ms poststimulus). Their firing was maximal during the 10–20 ms poststimulus epoch, while the slow layer IV cells fired maximally during the 20 – 30 ms poststimulus epoch. Surround inhibition occurred in all layers within the first 10 ms after stimulus onset, during which period the fast cells are the most active ones, and are thus likely to be responsible for the surround inhibition. This notion is supported by an analysis of spike duration that showed that eight of the ten cells with a thin spike (supposed to be GABAergic; McCormick et al., J. Neurophysiol., 54, 782 – 806, 1985), had PW latencies of <15 ms. We conclude that the activation of a barrel column is initially inhibitory in nature.
The Effects of Periaqueductally Injected Transmitter Antagonists on Forebrain‐elicited Vocalization in the Squirrel Monkey
Authors: Jürgens U. , Lu C.‐L.
Published: April 2006

In 15 squirrel monkeys, vocalization‐eliciting electrodes were implanted into the following forebrain structures: anterior cingulate cortex, genu of the internal capsule, amygdala, bed nucleus of the stria terminalis, hypothalamus, midline thalamus, inferior thalamic peduncle and periventricular grey. Then, injections of 29 transmitter antagonists were made into the midbrain periaqueductal grey (PAG) and their effects tested on the elicitability of vocalization from the forebrain. Vocalization could be blocked completely with glutamate antagonists. NMDA receptor antagonists as well as kainate/quisqualate receptor antagonists were effective. Facilitatory effects, i.e. a decrease in threshold of forebrain‐elicited vocalization, was obtained with GABA‐A receptor, glycine and opioid antagonists. The facilitatory effect of the opioid antagonist naloxone was limited to vocalizations expressing aversive emotional states. GABA‐A receptor antagonists not only facilitated forebrain‐induced vocalization but also produced vocalization themselves, i.e. without concomitant forebrain stimulation. No effects were obtained with antagonists of muscarinic and nicotinic receptors, with the GABA‐B receptor antagonist phaclofen and antagonists of the monoamines dopamine, noradrenaline, adrenaline, serotonin and histamine. It is concluded that the PAG represents a crucial relay station of the vocalization‐controlling system. In this station, transmission of vocalization‐relevant information depends upon the activation of glutamatergic synapses. Inhibitory control is exerted by GABA, glycine and endogenous opioids. Acetylcholine, dopamine, noradrenaline, adrenaline, serotonin and histamine may play a transient modulatory role; forebrain‐induced vocalization, however, does not depend upon the cholinergic or monoaminergic activation of PAG neurons.
Interactions of Dopamine with Glutamate‐ and GABA‐mediated Synaptic Transmission in the Rat Entorhinal Cortex In Vitro
Authors: Pralong E. , Jones R. S. G.
Published: April 2006

We have studied the interactions between dopamine and glutamate‐mediated transmission in the entorhinal cortex using intracellular recording in a slice preparation from the rat brain. High concentrations (0.1 – 1 mM) of dopamine had weak, direct effects on the membrane potential with predominantly hyperpolarizing responses in layer II neurons and depolarizing responses in layer V. Studies with the dopamine antagonists sulpiride (D2 antagonist, 10 – 50 μM) and SCH‐23390 (D1 antagonist, 50 μM) indicated that the hyperpolarization by dopamine could be mediated by D2 receptors, although the pharmacology was not clear‐cut. The depolarizing response was not affected by either D1 or D2 antagonists. Synaptic responses of layer II and layer V cells were complex, consisting of both inhibitory and excitatory potentials. In untreated slices, dopamine reduced all components of the synaptic responses. However, when components of the responses were pharmacologically isolated, only the excitatory, glutamate‐mediated potentials were consistently affected and the GABAergic inhibitory potentials were more resistant to reduction by dopamine. Excitatory potentials mediated by both N‐methyl‐d‐aspartate and α‐amino‐3‐hydroxy‐5‐methyl‐isoxazolepropionic acid receptors were reduced by dopamine, but the former were more strongly affected. Studies with antagonists suggested that the D1 receptor is more likely to be involved in the decrement of glutamate transmission. Thus, dopamine appears to modulate glutamate‐mediated synaptic transmission in the entorhinal cortex, and it is conceivable that a disturbance in this interaction could be involved in the aetiology of schizophrenia.
Positive and Negative Brain Zones in the Snail
Authors: Balaban Pavel M. , Maksimova Olga A.
Published: April 2006

Fine wire electrodes were surgically implanted in two regions of the brain of the snail Helix aspersa. To receive electrical stimulation of the brain, a tethered snail was required to displace the end of a rod. Self‐stimulation delivered to the parietal ganglion resulted in non‐repetition of the operant response, whereas self‐stimulation delivered to the mesocerebrum resulted in an increase in response frequency. The reinforcing effect of local extracellular stimulation of two brain zones was investigated in a semi‐intact preparation of a closely related species with an identical cellular map (H.lucorum). It was found that mesocerebral stimulation increased the frequency of the reinforced spontaneous movement, but decreased the frequency of the same movement if its absence was reinforced. These results allow us to attribute positive reinforcing effects to this brain area, which is involved in the control of sexual behaviour. Different results were obtained by contingent stimulation of the rostral part of the parietal ganglia, where giant cells controlling avoidance behaviour are located. Stimulation of this zone resulted in a decrease in the frequency of the ongoing spontaneous movements. These findings make possible intracellular investigations of the mechanisms of positive and negative reinforcement.
Failure to Induce Long‐term Depression by an Anti‐Correlation Procedure in Area CA1 of the Rat Hippocampal Slice
Authors: Paulsen O. , Li Y.‐G. , Hvalby Ø. , Andersen P. , Bliss T. V. P.
Published: April 2006

We have independently in our two laboratories re‐examined the report by Stanton and Sejnowski (Nature, 339, 215 – 218, 1989) that single stimuli to a test pathway in area CA1 of the hippocampal slice, when delivered between short bursts of stimuli to a second, convergent pathway, produce an associative long‐term depression (LTD) in the test pathway. While robust associative LTP was observed when stimuli to the two inputs were correlated in time, the anti‐correlation procedure failed to induce LTD; rather, a trend towards potentiation was observed. This result was obtained using both submerged and interface chambers, and in two different strains of rat. A transient depression lasting for a few minutes could usually be elicited by strong tetanic stimulation; this depression was not restricted to activated pathways.
Role of Voltage‐gated Ca2+ Channels and Intracellular Ca2+ in Rat Sympathetic Neuron Survival and Function Promoted by High K+ and Cyclic AMP in the Presence or Absence of NGF
Authors: Murrell Ruth D. , Tolkovsky Aviva M.
Published: April 2006

We have examined how NGF‐dependent rat sympathetic neurons maintain Ca2+ homeostasis when challenged with high K+ or 8‐(4‐chlorophenylthio)cyclic AMP (CPTcAMP), two survival factors. In the presence of NGF, high K+ (55 mM) caused a stable, 65% reduction in the density of cell soma voltage‐sensitive Ca2+ channels within 2 days. Although resting [Ca2+]i was elevated by 1.6‐fold, this was 50% less than the rise in [Ca2+]i measured before down‐regulation occurred, suggesting that down‐regulation may help prevent the toxic effects of persistently elevated [Ca2+]i. Inhibition of protein synthesis by cycloheximide blocked recovery from down‐regulation. Moreover, treatment with cycloheximide or actinomycin‐D caused a 2‐fold rise in the peak Ca2+ current, suggesting that voltage‐sensitive Ca2+ channel activity may be tonically attenuated during normal growth. In the absence of NGF, neurons survived for several days in high K+ medium with no significant rise in resting [Ca2+]i, although neurites did not grow. Neither Ca2+ channel density nor resting [Ca2+]i were altered in neurons surviving with CPTcAMP. Moreover, CPTcAMP lowered the dependence on extracellular Ca2+. However, the dihydropyridine antagonist nitrendipine blocked both high K+‐ and CPTcAMP‐dependent survival although it had no effect in the presence of NGF. Thus, in the absence of NGF, sympathetic neurons do not require elevation of [Ca2+]i above resting levels to survive with either high K+ or CPTcAMP, but dihydropyridine‐sensitive Ca2+ channel activity may be essential for their survival promoting actions.
Taurine Release Evoked by NMDA Receptor Activation is Largely Dependent on Calcium Mobilization from Intracellular Stores
Authors: Menéndez N. , Solis J. M. , Herreras O. , Galarreta M. , Conejero C. , del Río R. Martin
Published: April 2006

It is known that the activation of N‐methyl‐d‐aspartate (NMDA) receptors leads to an increase in extracellular taurine concentration in different brain regions. The mechanism that mediates this effect is not totally understood. In this study, rat hippocampal slices were used to determine the dependence of NMDA‐induced taurine release on extracellular calcium and/or on calcium mobilization from intracellular stores. NMDA was administered through a microdialysis probe inserted into the slice, at the level of CA1 stratum radiatum, which was also used to collect amino acids from the extracellular space. Field potentials evoked by stimulation of the Schaffer collaterals and recorded in the stratum pyramidale of CA1 were used as a control of NMDA receptor activation. NMDA induced a marked increase in extracellular taurine levels and a decrease in field potential amplitude, and both effects were suppressed in the presence of MK‐801, a blocker of the NMDA receptor‐linked channel. Dantrolene, an inhibitor of calcium release from intracellular stores, partially inhibited the extracellular taurine increase, while 2‐nitro‐4‐carboxyphenyl‐N,N‐diphenyl carbamate (NCDC), an inhibitor of phosphatidylinositol‐specific phospholipase C activation, had no effect. Removal of extracellular calcium diminished, but did not abolish, the extracellular taurine increase caused by NMDA. The remaining taurine response was totally suppressed by dantrolene, and also by NCDC. These results demonstrate that the release of taurine induced by NMDA receptor activation is triggered by the increase in cytoplasmic calcium concentration. We suggest that, under physiological conditions, calcium influx provides the signal for NMDA‐induced taurine release, which is amplified by calcium‐dependent calcium mobilization from intracellular stores. In the absence of extracellular calcium, NMDA is still able to evoke taurine release through a mechanism that implies calcium release from inositol 1,4,5‐trisphosphate‐sensitive stores.
Adenoviral Vector as a Gene Delivery System into Cultured Rat Neuronal and Glial Cells
Authors: Caillaud Catherine , Akli Said , Vigne Emmanuelle , Koulakoff Annette , Perricaudet Michel , Poenaru Livia , Kahn Axel , Berwald‐Netter Yoheved
Published: April 2006

Previous studies have demonstrated that a defective recombinant adenovirus can infect a wide range of postmitotic and slowly proliferating cell types such as hepatocytes, myotubes, pneumocytes and intestinal cells (Stratford‐Perricaudet et al., Hum. Gene Ther., 1, 241–256, 1990; Quantin et al., Proc. Natl. Acad. Sci. USA, 89, 2581–2584, 1992; Jaffe et al., Nature Genetics, 1, 372–378, 1992). We have used a defective recombinant adenovirus, Ad.RSVβgal, containing the Escherichia coliβ‐galactosidase gene targeted to the nucleus under the transcriptional control of the Rous sarcoma virus long terminal repeat promoter (Stratford‐Perricaudet et al., J. Clin. Invest., 90, 626–630, 1992) to infect non‐dividing neural cells in primary culture. We show that 80–100% of neuronal and astroglial cells infected with a viral titre lower than 109 p.f.u./ml express β‐galactosidase for at least 1 month without cell damage. These results demonstrate the potential usefulness of recombinant adenovirus infection for the analysis of brain‐specific gene regulation and for the transfer of genes into neural cells before their transplantation into the brain.
Increased Expression of GAP‐43, Somatostatin and Neuropeptide Y mRNA in the Hippocampus During Development of Hippocampal Kindling in Rats
Authors: Bendotti C. , Vezzani A. , Tarizzo G. , Samanin R.
Published: April 2006

The expression and distribution of the mRNA coding for the growth‐associated protein‐43 (GAP‐43), a putative marker for neuritic growth, for preprosomatostatin and the preproneuropeptide Y (ppNPY) were analysed in the rat hippocampus during the development of hippocampal kindling by an in situ hybridization technique and computer‐assisted grain counting in the cell. The levels of GAP‐43 mRNA increased significantly in the CA3 pyramidal neurons and hilar polymorphic neurons of the dentate gyrus 2 days after stage 2 of kindling (preconvulsive stage) but not stage 5 (full seizure expression) in the stimulated hippocampus. The distribution of GAP‐43 mRNA was the same in the hippocampus of kindled rats as in sham‐stimulated animals. Preprosomatostatin mRNA and ppNPY mRNA contents rose significantly in the hilar polymorphic neurons of the dentate gyrus of the stimulated and contralateral hippocampus at both stages of kindling, with the greatest effect at stage 5. In addition, the number of ppNPY mRNA neurons in the fascia dentata was significantly higher in kindled rats than in controls, but there were no differences in the number of preprosomatostatin mRNA‐positive cells. Preprosomatostatin and ppNPY mRNAs were also increased in the neurons of the stratum oriens of the CA1 ‐ CA3 subfield of fully kindled animals, whereas at stage 2 only neurons of the CA1 stratum oriens showed a significant increase of preprosomatostatin mRNA. No changes in preprosomatostatin and ppNPY mRNA expression were observed in the various regions of the hippocampus after a single afterdischarge or 1 month after stage 5. These data show that synthesis of somatostatin and neuropeptide Y increases in certain neurons of the hippocampus during the development of hippocampal kindling, and support the suggestion that these peptides are involved in epileptogenesis. Moreover, the increased synthesis of GAP‐43 may contribute to the synaptic remodelling of certain hippocampal neurons during kindling.
GAP‐43, aFGF, CCK and α‐ and β‐CGRP in Rat Spinal Motoneurons Subjected to Axotomy and/or Dorsal Root Severance
Authors: Piehl F. , Arvidsson U. , Johnson H. , Cullheim S. , Dagerlind Å. , Ulfhake B. , Cao Y. , Elde R. , Pettersson R. F. , Terenius L. , Hökfelt T.
Published: April 2006

The mRNA levels for growth‐associated protein 43 (GAP‐43), acidic fibroblast growth factor (aFGF), α and β‐calcitonin gene‐related peptide (CGRP), cholecystokinin (CCK) and choline acetyltransferase (ChAT) in rat lumbar spinal motoneurons were studied by in situ hybridization 1, 5 and 21 days and 20 weeks following unilateral peripheral nerve sectioning, ventral rhizotomy or dorsal rhizotomy. Furthermore, CGRP‐ and aFGF‐like immunoreactivities in the ventral horn were studied using immunohistochemistry. One to 21 days after axotomy, GAP‐43 and α‐CGRP mRNAs increased in lesioned motoneurons, while the aFGF mRNA levels were marginally higher in motoneurons on the lesion side as compared to the control side. β‐CGRP, CCK and ChAT mRNA levels, on the other hand, decreased during the short‐term response (1 – 21 days) to axotomy. After ventral rhizotomy, but not peripheral axotomy, there was complete disappearance of aFGF‐like immunoreactivity in the ventral root proximal to the lesion. In animals subjected to long‐term survival (20 weeks) after peripheral axotomy, the expression of all studied substances had returned to normal levels. Unilateral dorsal rhizotomy did not induce any substantial short‐ or long‐term shifts in the cellular expression of the GAP‐43, aFGF, CGRP and CCK peptides or their mRNAs in motoneurons of lesioned segments. These results indicate that peptides/proteins in motoneurons are expressed differentially after axotomy. Whereas α‐CGRP and GAP‐43 are up‐regulated, CCK and β‐CGRP become down‐regulated and aFGF is largely unaffected.
Alterations of G‐protein Coupling Function in Phosphoinositide Signalling Pathways of Rat Hippocampus by Ischaemic Brain Injury
Authors: Lu You M. , Lu Bu F. , Yan Yu L. , Yan Tin H. , Ho Xiaon P. , Wang Wen J.
Published: April 2006

The activation of membrane‐associated phospholipase C is rapidly and transiently induced in the central nervous system by a variety of stimuli. Ischaemic brain injury is one of the situations that leads to a dramatic increase in polyphosphoinositide (PPI) turnover. In this study, stimulation of PPI hydrolysis by glutamate (500 μM) was measured in hippocampal slices from rats up to 21 days after an ischaemic insult of 30 min. Ischaemia was induced using the four‐vessel occlusion method. PPI hydrolysis elicited by glutamate was significantly increased in the slices prepared from ischaemic rats 24 h after reperfusion, the accumulation of inositol phosphates (InsPs) and inositol 1,4,5‐trisphosphate (InsP3) was 614±74% (n= 8) and 182±11% (n= 9) of the basal level respectively. This potentiation was also observed 21 days after ischaemia. Hyper‐responsiveness to glutamate was also accompanied by an increase in AIF−4‐stimulated formation of [3H]inositol phosphates. In addition, global ischaemia did not change either high‐affinity [3H]glutamate binding in hippocampal membranes or the stimulation of PPI hydrolysis by carbachol or noradrenaline in hippocampal slices. The present results suggest that the increased responsiveness to glutamate is the result, at least in part, of functional changes at the G‐protein level, and may contribute to the pathophysiology of ischaemic brain injury or to the regenerative phenomena that accompany ischaemic damage.
The Contribution of Intracortical Connections to Horizontal Spread of Activity in the Neocortex as Revealed by Voltage Sensitive Dyes and a Fast Optical Recording Method
Authors: Albowitz B. , Kuhnt U.
Published: April 2006

Coronal slices from guinea‐pig visual neocortex were stained with voltage‐sensitive fluorescence dyes RH414 or RH795. Activity was evoked by electrical stimulation of either the white matter or layer I. Emitted light intensity changes representing summated changes of membrane potential were recorded by a 10 × 10 photodiode array with a temporal resolution of 0.4 ms and a spatial resolution of 94 μm. The distribution and spread of activity in the horizontal direction was analysed. Following stimulation of the white matter or layer I, two regions of activity were differentiated in the medio‐lateral direction: a central region (∼1 mm wide) of high‐amplitude activity close to the stimulation electrode and, distant from the stimulation electrode, peripheral regions of low‐amplitude activity. Central and peripheral regions differed in their rates of decline, their relative extent with stimulation of different sites and within different layers. The total extent of non‐synaptic evoked activity did not exceed that of the central region of high‐amplitude activity. Along the extent of non‐synaptic activity, onset latencies of potentials were almost constant. Thus, activity of high amplitude in the central region was likely mediated by simultaneous activation of distributed afferent fibres. In contrast, no non‐synaptic activity was found in peripheral regions. Therefore it is suggested that this low‐amplitude activity was mediated without direct afferent activation but via long‐distance intracortical horizontal pathways. These pathways are known to terminate in layer III, and accordingly latencies of responses in the periphery were shortest in upper cortical layers, whereas in the central region, latencies increased from lower to upper cortical layers.
Excitatory Drive from Deep Cerebellar Neurons to the Superior Colliculus in the Rat: an Electrophysiological Mapping Study
Authors: Max Westby G. W. , Collinson Christine , Dean Paul
Published: April 2006

The cerebello‐tectal projection arising from the interpositus nucleus was investigated electrophysiologically to test the hypothesis that the deep cerebellar nuclei constitute a source of tonic excitation in the superior colliculus. A total of 117 spontaneously active collicular neurons were recorded during GABA microinjection into 26 interpositus sites, where tonic single‐cell deep cerebellar activity was also simultaneously recorded. GABA injection always led to suppression of interpositus activity, while in the colliculus a clear pattern of results emerged. 58% of superior colliculus cells showed no response to suppression of interpositus activity, 35% showed a frequency decrease and 7% showed a frequency increase. The majority of these responsive cells were found in a laterally located sheet of cells mainly restricted to the intermediate white layer, in close register with the known cells of origin of the predorsal bundle and completely overlapping the terminals of the nigrotectal pathway originating in dorsolateral substantia nigra pars reticulata. The implications of these results for cooperative theories of head movement control involving the superior colliculus, cerebellum and precerebellar nuclei are discussed.
Development of Calbindin‐D28k Immunoreactive Neurons in the Embryonic Chick Lumbosacral Spinal Cord
Authors: Antal Miklós , Polgár Erika
Published: April 2006

The development of immunoreactivity for the calcium‐binding protein calbindin‐D28k (CaB) was investigated in the embryonic and hatched chick lumbosacral spinal cord. CaB‐immunoreactive neurons were revealed in the dorsal and ventral horns as well as in the intermediate grey matter from early stages of neuronal development. CaB immunoreactivity was first detected in large neurons in the presumptive dorsal horn at embyronic day 5, while small neurons in the lateral dorsal horn were the last to appear, at embryonic day 10. We have identified and traced the morphological maturation of six CaB‐immunoreactive cell groups, three in the dorsal horn and three in the ventral horn. In the dorsal horn these groups were (1) large neurons in the lateral dorsal horn (laminae I and IV), (2) small neurons in the lateral dorsal horn (lamina II), and (3) small neurons in the medial dorsal horn (lamina III). All three groups were present throughout the entire length of the lumbosacral spinal cord and showed persistent CaB immunoreactivity. In the ventral horn, CaB‐immunoreactive neurons were classified into the following three categories: (1) Neurons dorsal to the lateral motor column (lamina VII). These neurons were present exclusively in the upper lumbosacral segments (LS1 – 3), and they showed steady CaB immunoreactivity during their maturation. (2) Neurons at the dorsomedial aspect of the lateral motor column (at the border of laminae VII and IX). This population of neurons was characteristic of the lower segments of the lumbosacral cord (LS5 – 7) and presented transient CaB expression. (3) Neurons within the lateral motor column (lamina IX). These neurons were dispersed throughout the length of the lumbosacral spinal cord. They were three to four times more numerous in the upper than in the lower lumbosacral segments, and their numbers declined throughout LS1 – 7 as the animal matured. The characteristic features of the development of neurons immunoreactive for CaB are discussed and correlated with previous neuroanatomical and physiological studies concerning sensory and motor functions of the developing chick spinal cord.
βAPP Gene Expression is Increased in the Rat Brain After Motor Neuron Axotomy
Authors: Solà Carme , García‐Ladona F. Javier , Sarasa Manuel , Mengod Guadalupe , Probst Alphonse , Palacios Gabriel , Palacios José M.
Published: April 2006

The response of the βAPP gene to neuronal injury was studied in the facial and hypoglossal nerve nuclei of the rat after corresponding nerve axotomy. Increased levels of βAPP 695, 714, 751 and 770 mRNAs were observed after either facial or hypoglossal nerve axotomy in the parent ipsilateral motor neurons. The increase was gradual, with maximal values 7 days after axotomy. βAPP mRNA expression returned to normal values 60 days after the lesion. Increased βAPP immunostaining was also detected in ipsilateral chromatolytic motor neurons. No change in βAPP immunoreactivity was observed in oligodendrocytes, another cell type expressing βAPP under normal conditions. A rapid increase in the expression of the GFAP gene was observed in reactive astrocytes surrounding chromatolytic neurons in the ipsilateral facial or hypoglossal nuclei. Thus, in contrast with other models of neuronal injury, where only the Kunitz protease inhibitor‐containing βAPP mRNA isoforms are increased, all βAPP mRNAs are increased in the axotomy model. Furthermore, although βAPP expression has been shown to be increased in reactive astrocytes following neuronal injury, in the present study the increase was essentially found in the motor neurons reacting to axotomy.