bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantification of Normal Cell Death in the Rat Retina: Implications for Clone Composition in Cell Lineage Analysis
Authors: Voyvodic James T. , Burne Julia F. , Raff Martin C.
Published: April 2006

Naturally occurring cell death complicates the analysis of cell lineage studies by making the surviving members of a clone appear more closely related than they actually are. Here we ask how much normal cell death occurs during rat retinal development, and whether that amount of death is sufficient to confuse the analysis of cell lineage relationships. We measure total cell death in the retina by combining relative counts of dead cells with absolute measurements of total cell loss. For most cell types, but not rods, we find that half of the cells generated die during normal retinal development. We use a computer model to quantify the effects of different amounts of cell death in a simulated lineage study. The simulation indicates that 50% cell death means that clonal variability analysed after the cell death period is not necessarily a good indicator of how much variability actually occurs in the underlying lineage.
Inhibition of PC12 Cell Attachment and Neurite Outgrowth by Detergent Solubilized CNS Myelin Proteins
Authors: Rubin Beatrix P. , Spillmann Adrian A. , Bandtlow Christine E. , Hillenbrand Rainer , Keller Flavio , Schwab Martin E.
Published: April 2006

Adhesion and neurite outgrowth of PC12 cells, as well as the spreading of 3T3 fibroblasts, were inhibited in a dose dependent manner by detergent solubilized mouse central nervous system myelin proteins as a tissue culture substrate. These inhibitory effects could be neutralized by the monoclonal antibody IN‐1 directed against the neurite growth inhibiting proteins NI‐35 and NI‐250. Separation of the detergent soluble proteins of bovine spinal cord by an anion exchange column showed that the peaks of inhibitory activity for the two cell lines overlapped, such that the PC12 cells were inhibited by a larger number of fractions comprising those inhibitory for 3T3 cells. Neurite outgrowth of PC12 cells was not influenced by the myelin associated glycoprotein, MAG.
Effects of Changes in Rat Brain Glucose on Serotonergic and Noradrenergic Neurons
Authors: Vahabzadeh Abdolvahab , Boutelle Martyn G. , Fillenz Marianne
Published: April 2006

Microdialysis was used in the freely moving rat to measure the effects of graded changes in brain glucose on the serotonergic and noradrenergic projections to the hippocampus. The concentration of glucose in the dialysate was monitored using an enzyme‐based assay. A systemic injection of insulin caused a steep decline in glucose level which was restored to the control level by oral administration of glucose solution. The changes in 5‐hydroxytryptamine (5‐HT) and noradrenaline were a mirror image of the glucose changes: they rose after insulin injection and returned to control during glucose administration. A delayed increase was shown by 5‐hydroxyindoleacetic acid (5‐HIAA) which did not return to baseline on glucose administration. The metabolite dihydroxyphenylacetic acid (DOPAC) decreased after insulin administration and increased above control during glucose administration. While the responses of 5‐HT, noradrenaline and 5‐HIAA to hypoglycaemia resemble those to mild stress, the changes in DOPAC are the reverse of those produced by stress.
Identification, Distribution and Physiological Activity of Three Novel Neuropeptides of Lymnaea: FLRlamide and pQFYRlamide Encoded by the FMRFamide Gene, and a Related Peptide
Authors: Santama Niovi , Wheeler Colin H. , Skingsley David R. , Yeoman Mark S. , Bright Kerris , Kaye Iain , Burke Julian F. , Benjamin Paul R.
Published: April 2006

We are interested in analysing the detailed modulation of defined neuronal systems by multiple neuropeptides encoded in the FMRFamide locus of the snail Lymnaea. Cloning of the FMRFamide gene has predicted the existence of two novel peptides previously unknown from biochemical analysis, the pentapeptides EFLRlamideand QFYRlamide. These peptides may form part of a new family of peptides sharing the sequence motif –FXRlamide. In this paper we adopt a novel approach to first identify and characterize –FXRlamide‐like peptides in extracts from the central nervous system of Lymnaea. By a combination of high‐performance liquid chromatography (HPLC) and continuous‐flow fast atom bombardment mass spectrometry, we identify three novel peptides: EFLRlamide, pQFYRlamide and pQFLRlamide. The first two are those predicted in exon II of the FMRFamide locus whereas the last is, interestingly, a product which cannot be derived from post‐translational modification of the predicted peptides but must be encoded by as yet unidentified nucleotide sequences. A specific antibody raised to EFLRlamide, and immuno reactive to all three peptides, revealed EFLRlamide‐like expression throughout the central nervous system in the same cells where exon II is transcribed and the peptide SEEPLY (a post‐translational product of exon II) was localized. Additional cells, however, were also identified. Immunoreactivity was mapped in a number of identified neurons in the central nervous system, including two heart cardio excitatory motoneurons, the Ehe cells (E heart excitors of the visceral ganglion) and penialmotoneurons in the right cerebral ganglion. The peripheral tissues (heart and penial complex) that the serespective classes of neurons innervate also exhibited EFLRlamide immunoreactivity. The central and peripheral localization of EFLRlamide‐like immunoreactivity suggested that EFLRlamide/pQFYRlamide may have an important physiological role in both these peripheral systems as well as in the central nervous system. This was confirmed by physiological experiments that showed that EFLRlamide and pQFYRlamide inhibited many centralneurons and in particular the Bgp neurons in the right parietal ganglion. EFLRlamide had complex biphasic effects on the frequency of heart‐beat: an initial inhibitory response was followed by a long‐lasting increase in the rate of beating. Taken together with earlier work, this study now completes the analysis and localization of the full set of post‐translational products of the FMRFamide precursor in Lymnaea and supplies further evidence towards the characterization of the physiological systems which such peptides may modulate in concert.
NMDA Receptor‐dependent Long‐term Potentiation in the Hippocampal Afferent Fibre System to the Prefrontal Cortex in the Rat
Authors: Jay Thérèse M. , Burette François , Laroche Serge
Published: April 2006

This study investigated the role of the N‐methyl‐d‐aspartate (NMDA) subtype of glutamate receptor in the induction of long‐term potentiation (LTP) in the hippocampal‐prefrontal cortex pathway in vivo. Field potentials evoked by electrical stimulation of the CA1/subicular region were recorded in the prelimbic area of the prefrontal cortex under continuous perfusion of artificial cerebrospinal fluid in anaesthetized rats. High‐frequency stimulation of the CA1/subicular region induced LTP of the evoked response in the prelimbic area of the prefrontal cortex. LTP was completely blocked when the selective NMDA receptor antagonist d‐(‐)2‐amino‐5‐ phosphonopentanoic acid (d‐AP5; 200 μM), was perfused during the tetanus. Perfusion of D‐AP5 did not affect normal transmission or pre‐established LTP. These results demonstrate that induction of LTP in the hippocampal‐prefrontal cortex pathway is an NMDA receptor‐dependent process.
The Effects of AMPA‐induced Lesions of the Septo‐hippocampal Cholinergic Projection on Aversive Conditioning to Explicit and Contextual Cues and Spatial Learning in the Water Maze
Authors: McAlonan Gráinne M. , Wilkinson Lawrence S. , Robbins Trevor W. , Everitt Barry J.
Published: April 2006

The environmental context of an animal both subsumes and is associated with the explicit cues that guide its behavioural responses. Recent work in this laboratory suggests that learning about the relationship between the cues which comprise a context depends on the hippocampus. In the present study the role of the cholinergic input to the hippocampus in contextual learning was assessed in rats using a conditioned stimulus/context conditioning paradigm and spatial learning in the Morris water maze. In the former, a place preference apparatus provided the context. The subject was confined in the black chamber and a ‘clicker’conditioned stimulus was presented five times in a 20 min period. A trace interval of 5 or 30 s, depending on the group, was interposed between the end of the clicker and a footshock. Theory predicts that animals in the 5 s condition will learn more about the clicker as a predictor of shock and become strongly conditioned, while those in the 30 s condition learn relatively more about the context. Conditioning to the clicker (conditioned stimulus) was measured in a separate lick suppression chamber—presentation of the clicker suppresses drinking, and contextual learning was determined by recording the time spent on the black side of the place preference apparatus when both the black and a familiar white chamber were accessible. Lesions of the medial septum/ diagonal band induced by RS‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) enhanced contextual learning in this paradigm but disrupted conditioned stimulus conditioning in the 30 s condition. Acquisition of the Morris water maze was largely unimpaired. The results are suggested to reflect a shift towards the use of hippocampal‐dependent contextual learning strategies in lesioned animals.
Changes in Protein Kinase C and its Presynaptic Substrate B‐SO/GAP‐43 after Intrauterine Exposure to Methylazoxy‐methanol, a Treatment Inducing Cortical and Hippocampal Damage and Cognitive Deficit in Rats
Authors: Di Luca M. , Caputi A. , Cinquanta M. , Cimino M. , Marini P. , Princivalle A. , De Graan P. N. E. , Gispen W. H. , Cattabeni F.
Published: April 2006

The involvement of protein kinase C (PKC)‐dependent processes in adaptive and plastic changes underlying neuronal plasticity was tested in an in vivo animal model characterized by targeted cellular ablation of cortical and hippocampal neurons, cognitive impairment and lack of induction of long‐term potentiation. [3H]Phorbol ester binding performed on brain slices revealed a 67.4 and 35.0% increase in membrane‐bound protein kinase C in the cortex and hippocampus respectively of rats treated with methylazoxy‐methanol acetate compared with saline‐treated control rats, and there was no modification in the expression of mRNAs of different protein kinase C isozymes. In situ phosphorylation experiments performed with 32Pi‐labelled synaptosomes from the affected areas demonstrated that the phosphorylation of the nervous tissue‐specific presynaptic membrane‐associated protein kinase C substrate B‐50lGAP‐43 was increased by 51.4 and 44.8% in cortex and hippocampus respectively. Western blot analysis of protein kinase C in synaptosomal cytosol and membrane fractions prepared from cortex and hippocampus showed an increased proportion of protein kinase C in the membrane compartment in treated animals, but no change in the total synaptosomal protein kinase C activity. Our data are consistent with increased activity of presynaptic protein kinase C and predict a sustained increase in glutamate release in methylazoxy‐methanol‐treated rats.
Quasi‐reversible Photo‐axotomy Used to Investigate the Role of Extensor Muscle Tension in Controlling the Kick Motor Programme of Grasshoppers
Authors: Heitler W. J.
Published: April 2006

The jump and kick of the grasshopper are behaviours which are potentially critical for the survival of the animal, and whose maximal Performance depends upon optimizing the rate and level of tension development in the extensor tibiae muscle of the hind legs. In experimental conditions extensor tension control can be reduced to a single motoneuron, the fast extensor tibiae (FETi). The axon of FETi can be cut using dye‐mediated laser photo‐ axotomy without damaging the central or peripheral portions of that neuron or any other neuron innervating the leg. The axotomy can be functionally reversed (i.e. the cut axon repaired) by an electronic axonal bypass which detects FETi spikes on the proximal side of the cut and stimulates the axon on the distal side of the cut. In this way motor spikes can either be allowed to reach the muscle or prevented from doing so (by switching the bypass on or off), and the motor programmes produced with and without extensor tension can be compared. The jump and kick are normally produced by a three‐stage motor programme: (i) initial flexion brings the tibia into the fully flexed position; (ii) coactivation of extensor and flexor muscles allows the extensor muscle to develop maximal tension almost isometrically, while the simultaneous contraction of the flexor muscle holds the tibia flexed; (iii) sudden trigger inhibition of the flexor system (motoneurons and muscle) releases the tibia and allows the behaviour to be expressed. The grasshopper can produce fictive kicks with motor programmes which show each of these three major structural features of a normal kick, but without any extensor tension whatsoever. There is no significant difference in the frequency of FETi spikes, the duration of coactivation or the maximum depolarization of the flexor motoneurons between fictive and quasi‐normal (i.e. reversed axotomy) kicks. The trigger inhibition of flexor motoneurons is shallower in fictive than in quasi‐normal kicks. The significance of this is discussed in relation to the activity of the interneuron M, which is known to mediate trigger inhibition onto FlTi motoneurons. There are two main conclusions from this study. First, the CNS does not need feedback from ETi muscle tension in order to produce the three‐stage motor programme of the kick (and, by implication, the jump). Second, the CNS does not adjust the frequency or duration of FETi activity in response to unexpected changes in ETi tension. ETi tension appears to be under open‐loop control in the kick motor programme.
Evidence for a High‐affinity Uptake System for Cholecystokinin Octapeptide (CCK8) in Rat Cortical Synaptosomes
Authors: Migaud Martine , Roques Bernard P. , Durieux Christiane
Published: April 2006

Given the high resistance of the cholecystokinin octapeptide (CCK8) to in vivo peptidase degradation, the possible existence of a reuptake system for this peptide was investigated. Efficient accumulation of intact, tritiated propionyl CCK8 ([3H]pCC8) was observed following its incubation with rat cortical synaptosomes but not with cerebellar synaptosomes, where no cholecystokinin immunoreactivity was found. This uptake process appeared to be dependent on temperature, duration of incubation, concentration of radioligand, the presence of glucose and the integrity of the synaptosomes. A Lineweaver‐Bürk analysis indicated that the putative uptake process is characterized by a single Km value of 10.7 nM and a Vmax of 8.5 fmol/min/mg of protein. Carbonyl cyanide‐m‐chlorophenyl hydrazone, an uncoupler of oxidative phosphorylation, blocked accumulation of [3H]pCCK8, whereas ouabain did not. The uptake was found to be highly specific since, among all the cholecystokinin analogues tested, only CCb and, to a lesser extent, CCK7, were able to inhibit [3H]pCCK8 uptake. The rate of [3H]pCCK8, uptake was not affected by CCK4, CCK5, D‐Trp CCK8, BC 264, a potent and selective CCK‐B agonist, and L‐365,260, a selective CCK‐B antagonist. In addition, no accumulation of radioactivity was observed using [3H]pBC 264, a result which is not in favour of a cholecystokinin receptor‐induced internalization mechanism. The potent and selective uptake mechanism characterized in this study could participate, in conjunction with extra and intracellular degradation of CCK8 by peptidases, in the interruption of cholecystokinin‐conveyed messages in the brain.
Human Recombinant Nerve Growth Factor Replaces Deficient Neurotrophic Support in the Diabetic Rat
Authors: Fernyhough Paul , Diemel Lara T. , Hardy Jim , Brewster Wendy J. , Mohiuddin Liza , Tomlinson David R.
Published: April 2006

Manipulation of neurotrophic support is a developing strategy for new therapy aimed at neurodegenerative diseases. This study demonstrates reduced content and retrograde transport of endogenous nerve growth factor (NGF) in sciatic nerve of diabetic rats. There were also reductions in the diabetic rats in NGF protein and mRNA in skin and muscle of the hindlimb. These deficits correlated with reductions in substance P and calcitonin gene‐related peptide–both products of NGF‐influenced genes in primary afferents. These manifestations of deficient neurotrophic support were corrected by intensive insulin treatment and surmounted by administration of exogenous human recombinant NGF in a dose‐related manner. Impaired neurotrophic support may, therefore, participate in the pathogenesis of diabetic and other peripheral neuropathies.
TrkA Tyrosine Residues Involved in NGF‐induced Neurite Outgrowth of PC12 Cells
Authors: Inagaki Naoyuki , Thoenen Hans , Lindholm Dan
Published: April 2006

The proto‐oncogene product gp 140prototrk (TrkA) is the receptor tyrosine kinase that mediates nerve growth factor‐induced neuronal survival and differentiation. In receptor tyrosine kinases, specific intracellular tyrosine residues become phosphorylated after ligand binding and the phosphorylated tyrosines induce the cascade of signal transduction. Here we have identified intracellular tyrosine residues of TrkA involved in nerve growth factor‐induced neurite outgrowth of PC12 cells, using site‐directed mutagenesis and a PC12 cell line expressing very low levels of endogenous TrkA (PC12nnr5 cells). We analysed eight conserved intracellular tyrosine residues of TrkA while the three putative autophosphorylation sites conferring tyrosine kinase activity were left intact. Five tyrosine residues, Y499, Y643, Y704, Y760 and Y794, in rat TrkA were involved in nerve growth factor‐induced neurite outgrowth. None of these tyrosines mediated the full activity of wild‐type TrkA, and a pair of these tyrosines, Y760 and Y794, promoted neurite outgrowth in an additive manner. These data indicate that no single tyrosine is sufficient to induce complete neurite outgrowth but the five tyrosine residues Y499, Y643, Y704, Y760 and Y794 cooperate to exhibit the full activity of wild‐type TrkA.
CO2 Stimulation of the Cornea: A Comparison Between Human Sensation and Nerve Activity in Polymodal Nociceptive Afferents of the Cat
Authors: Chen Xiaojie , Gallar Juana , Pozo Miguel A. , Baeza Manuel , Belmonte Carlos
Published: April 2006

Excitation of nociceptors by low pH has been proposed as a cause of pain following tissue injury. Here we have studied the effect of pH reductions caused by application of CO2 pulses to the cornea on the activity of corneal afferent nerves of the cat and on the magnitude of pain sensations in humans. Single‐unit activity was recorded from corneal afferent fibres in anaesthetized cats. The corneal receptive field of A‐delta or C polymodal nociceptive units was exposed for 30 s to a gas mixture with different concentrations of CO2 in air (0, 35, 50, 65, 80 and 98.5%). Responses to CO2 were evoked at a mean threshold concentration of 40 ± 3% CO2. They consisted of a discharge of impulses that decayed gradually to a tonic level. In 15% of the units the initial burst was absent. The CO2 concentration and firing frequency data could be fitted to a power function with an exponent of 1.12. Pulses of CO2 were also applied to the cornea of 16 human volunteers. Sensations experienced were measured by means of a visual analogue scale and a verbal descriptor scale. Flow was adjusted below the mechanical stimulation threshold (2.8 ± 0.5 mg). When mixtures containing 10‐90% CO2 in 5% steps were applied as 3 s pulses, threshold sensation, described as a mild stinging pain, was evoked at 33.5 ± 4.0% CO2. This sensation became overtly painful with higher CO2 concentrations (47.5 ± 3.6% CO2). For the same subject the sensory threshold was remarkably constant, though it changed with longer exposure times. The relationship between CO2 concentration and magnitude of pain could be adjusted to a power function with a power exponent of 1.12. Curves of CO2 concentration versus neural discharges in the cat and versus psychophysical sensation in humans were very similar. These results show that corneal polymodal nociceptors respond to protons, and encode changes in CO2 concentration presumably reflecting pH changes. The same stimulus evokes corneal pain sensations in humans, thus opening the possibility of using CO2 as an effective stimulus for corneal aesthesiometry.
Gamma‐range Activity Evoked by Coherent Visual Stimuli in Humans
Authors: Tallon Catherine , Bertrand Olivier , Bouchet Patrick , Pernier Jacques
Published: April 2006

We tested the hypothesis of a role of gamma‐range synchronized oscillatory activity in visual feature binding by recording evoked potentials from 12 subjects to three stimuli: two coherent ones (a Kanizsa triangle and a real triangle) and a non‐coherent one (a Kanizsa triangle in which the inducing disks had been rotated so that no triangle could be perceived). The evoked potentials were analysed by convoluting the signal for each subject and each stimulation type by Gabor wavelets centred from 28 up to 46 Hz, providing a continuous measure of frequency‐specific power over time. A first peak of activity was found around 38 Hz and 100 ms with a maximum at electrode Cz in each experimental condition. A second peak of activity occurred around 30 Hz and 230 ms, with a maximum at O1 in response to the real triangle and a maximum at Cz in the case of the illusory triangle. At 100 ms we did not find any variations of the gamma‐band component of the evoked potential with stimulation type, but the power of the 30 Hz component of the evoked potential between 210 and 290 ms differed from noise only in the case of a coherent triangle, no matter whether real or illusory. We thus found a 30 Hz component whose power correlates with stimulus coherency, which supports the hypothesis of a functional role of high‐frequency synchronization in feature binding. Moreover, this correlation seemed specific to the gamma‐frequency range, as neither the power of the low‐frequency components (0–25 Hz) nor the power of the electromyogram range components (60–80 Hz) showed the same effect.
Ultrastructural Changes in the Hydropic Cochlea of the Guinea‐pig
Authors: Horner K. C. , Guilhaume A.
Published: April 2006

Transmission electron microscopy of the cochlear organ of Corti in experimental endolymphatic hydrops revealed two principal features. Starting 1 month after induction of hydrops, osmiophilic inclusions thought to represent lipofuscin accumulation were frequently observed in the subcuticular cytoplasm of the outer hair cells along the length of the cochlea. Starting 3 months after induction of hydrops the efferent terminals on the outer hair cells appeared to be vacuolated. These data suggest that oxidative insult is likely to contribute to the pathology associated with endolymphatic hydrops and thus that free radical scavengers might be useful in the treatment of Menière's disease patients. In addition the early modification of the efferent innervation of the hydropic cochlea might underlie the known hypersensitivity to various insults, including noise stimulation, glycerol administration and hypoxia.
Inhibitors of Cyclooxygenases produce Amnesia for a Passive Avoidance Task in the Chick
Authors: Hölscher Christian
Published: April 2006

Arachidonic acid is a putative messenger in synaptic transmission which presumably plays a role in learning and memory. Previous experiments showed that inhibitors of phospholipase A2‐dependent release of arachidonic acid cause amnesia in a one‐trial passive avoidance task in the chick. To test if arachidonic acid is metabolized to other messengers, the effects of inhibitors of enzymes which metabolize arachidonic acid were tested in the same task. The cyclooxygenase inhibitors indomethacin, naproxen and ibuprofen caused amnestic effects at all concentrations tested when injected intracerebrally before training. Injections were 5 μl of 5–20 mmolar solutions per hemisphere. The onset of amnestic effects was always 2 h after training, independently of drug type, concentration, and injection time before training. The delay of 2 h after training suggests that the drugs prevent induction of cyclooxygenase synthesis. Post‐training injections had no effect. Control tests showed little effect of the drugs on motor control and motivation. Caffeic acid and esculetin, inhibitors of lipoxygenases, and sodium furegrelate, a thromboxane synthase inhibitor, had no effect on performance of chicks in the task at all concentrations or time points tested. The results indicate that cyclooxygenase products, but not lipoxygenase or thromboxane synthase products, play a role in memory consolidation in the chick when learning this task.
Calmodulin and In Vitro Regenerating Frog Sciatic Nerves: Release and Extracellular Effects
Authors: Remgård Pär , Ekström Per A. R. , Wiklund Peter , Edström Anders
Published: April 2006

Although calmodulin (CaM) is commonly considered to be an intracellular protein, it has been suggested lately that it is released and exerts functions extracellularly. In the present investigation this was studied in in vitro regenerating adult frog (Rana temporaria) sciatic nerves. Using a multi‐compartment incubation chamber, the non‐neuronal cells in the outgrowth region of such nerves were radiolabelled with amino acid precursors. Based on immunological criteria, these cells were shown to release CaM. When the nerves were treated with CaM, both the outgrowth of sensory axons and the injury‐induced proliferation of non‐neuronal cells were partially inhibited. The inhibitory effects occurred even when the incubation medium contained as little as 30 pM CaM. Furthermore, treatment with anti‐CaM antibodies resulted in reduced outgrowth, which suggested that during normal conditions extracellular CaM is kept at an optimal concentration. Finally, conditioned medium was found to contain several CaM‐binding proteins. The present findings may reflect an earlier unknown function of extracellular CaM in controlling various growth mechanisms in integrated tissues.
Truncated and Catalytic Isoforms of trkB are Co‐expressed in Neurons of Rat and Mouse CNS
Authors: Armanini M. P. , McMahon S. B. , Sutherland J. , Shelton D. L. , Phillips H. S.
Published: April 2006

Localization of mRNA encoding trkB indicates that two truncated isoforms of trkB, T1trkB and T2trkB, are differentially distributed in the rodent nervous system, and that each of these transcripts is co‐expressed with catalytic trkB (TK+trkB) in adult motor neurons. In contrast to the prominent expression of T1trkB by non‐neuronal cells, T2trkB expression appeared to be restricted to neurons and demonstrated significant overlap with the pattern of TK+trkB distribution. In developing spinal cord ventral horn, an age‐related increase in hybridization was observed for truncated isoforms. These findings suggest that truncated trkB may modulate neuronal responses to neurotrophins which act via trkB.
Orienting Behaviour and Superior Colliculus Sensory Representations in Mice with the Vibrissae Bent into the Contralateral Hemispace
Authors: Benedetti F.
Published: April 2006

When a tactile stimulus touches the body on one side, animals show an orienting response toward that side with the eyes, the head or the entire body. This movement requires the transformation of sensory information into motor commands. The superior colliculus is supposed to be a fundamental part of the brain where this sensorimotor transformation occurs and where one of the possible mechanisms could be the alignment among sensory and motor topographies. We changed the body shape of mice in order to analyse the development of new orienting responses following tactile stimulation. To do this, we bent the left vibrissae from left to right such that they were located in the right portion of the visual hemifield. If left‐right inversion was performed in adults, tactile stimulation of the left vibrissae performed from the right produced wrong orienting movements to the left. Conversely, if left—right inversion was performed in newborns, mice learned to respond correctly to the right. By recording from superior colliculus multisensory neurons of mice whose vibrissae were displaced at birth, we found a shift of visual and auditory receptive fields from left to right in those multisensory neurons receiving tactile input from the displaced vibrissae. These results show the strict relation existing between the neuronal modifications in the superior colliculus and the changes in orienting behaviour. These findings also suggest two important conclusions. First, sensory mapping in the superior colliculus depends on sensory inputs coming from the same portion of space. Second, since the neuronal modifications we found involved sensory representations, the observed motor learning seems to be due, at least in part, to sensory changes, and the superior colliculus appears therefore to be an important brain region where the internal schema of the body is specified.
Human Motor Planning, Motor Programming, and Use of New Task‐relevant Information with Different Apraxic Syndromes
Authors: Platz T. , Mauritz K.‐H.
Published: April 2006

Patients with ideomotor apraxia (n= 2) or ideational apraxia (n= 2) after left brain stroke and patients with constructional apraxia (n= 2) after cerebrovascular accident of the right hemisphere, as well as 16 non‐brain‐damaged control subjects, were given a standardized simple motor task: they were asked to make triangular arm movements of specific size, configuration and spatial orientation without visual control. Motion was analysed three‐dimensionally in great detail prior to and after kinaesthetic training using a triangular stencil, and 1 day later. The experiment was conceptualized to assess three aspects of motor behaviour: (i) motor planning, operationalized as specification of content parameters of the movement as a whole; (ii) motor programming, the specification of spatiotemporal parameters of movement segments; and (iii) the ability to make use of task‐relevant information provided by the training. Patients with ideational apraxia showed signs of impaired motor planning: they had difficulty in selecting the body parts to be moved, and movement concept and configurational aspects were deficient. The kinaesthetic sensorimotor training given seemed not adequate to reduce behavioural deficits. Kinematic peculiarities of patients with ideomotor apraxia can be understood as deficits in programming movement elements. Submovements were more segmented, showed irregularities as well as additional, not‐requested elements. Their impairments could be reduced by task‐specific sensorimotor training. Patients suffering from visuoconstructive apraxia after right brain damage might have difficulties in making use of new sensorimotor information relevant for spatial‐motor aspects, as suggested by training‐induced behavioural impairment with a severely constructional apraxic patient.
Corticosteroid Regulation of Gene Expression and Binding Characteristics of Vasopressin Receptors in the Rat Brain
Authors: Patchev Vladimir K. , Almeida Osborne F. X.
Published: April 2006

Arginine‐vasopressin (AVP) plays significant roles in neuroendocrine and autonomic regulation, and in processing of cognitive information. Its synthesis and secretion are subject to control by circulating glucocorticoids. The lateral septum and subdivisions of the hippocampus are innervated by AVP‐ergic fibres and, together with AVP‐producing neurons in the hypothalamic paraventricular nucleus, are major neural targets of glucocorticoid negative feedback. In this study, we investigated the effects of chronic adrenalectomy (ADX) and subsequent treatment with supraphysiological doses of corticosterone (B) on the gene expression of AVP receptors of the V1a subtype in the septum, hippocampus and hypothalamic arcuate (ARC) nucleus using semiquantitative in situ hybridization histochemistry. Adrenalectomy did not alter AVP receptor expression in any of the structures studied. Supplementation with B significantly decreased AVP receptor expression in the lateral septum and hippocampus, whereas receptor mRNA levels in the ARC were indistinguishable from those measured in controls. In a complementary study, we investigated the binding characteristics of V1 AVP receptors in membrane preparations from the hippocampus. Adrenalectomy significantly decreased the number of AVP binding sites, and chronic corticosteroid treatment was associated with a further suppression of AVP receptor concentrations in this structure. These results indicate that the gene transcription of V1a AVP receptors in the brain is regulated by circulating glucocorticoids in a site‐specific fashion that largely reflects the corticosteroid sensitivity of the corresponding structure. The comparison between corticosteroid‐induced changes in receptor binding and gene transcription in the hippocampus suggests that two separate mechanisms may be operational in the regulation of AVP receptors by glucocorticoids: increased AVP release probably accounts for the observed down‐regulation in receptor binding following ADX, whereas increased corticosteroid levels interfere with AVP receptor expression.
The Unique Characteristics of Inflammatory Responses in Mouse Brain are Acquired During Postnatal Development
Authors: Lawson Linda J. , Perry V. Hugh
Published: April 2006

The kinetics of leukocyte recruitment during acute inflammation in adult mouse brain differ from the stereotyped response occurring in non‐CNS tissues; neutrophil recruitment is minimal and monocyte recruitment occurs after a 48 h delay. One aspect of the CNS microenvironment which may contribute to restricted leukocyte recruitment is the highly differentiated nature of resident CNS macrophages, the microglia. Thus we studied the inflammatory response to intracerebral injections of endotoxin in neonates in which microglia are less differentiated and resemble more closely macrophages of non‐CNS tissues. Mice injected with endotoxin on the day of birth exhibited both neutrophil and monocyte recruitment to the parenchyma, but the response differed from that occurring in non‐CNS tissues such as skin. Leukocyte recruitment was very slow, the mononuclear phagocyte response peaking 14 days after endotoxin injection. This sluggish inflammatory response was reminiscent of that previously described in fetal wounds. However, when endotoxin was injected into brains of 7‐day‐old neonates the inflammatory response resembled that seen in non‐CNS tissues; i.e. prolific neutrophil recruitment and a brisk mononuclear phagocyte response. Thus the unusual inflammatory cell kinetics are a property of the mature CNS microenvironment; all signals necessary to support typical leukocyte recruitment are present in the brain by 7 days of age but the brain becomes able to restrict leukocyte immigration during subsequent postnatal development. Developmental changes in the host response to identical inflammatory challenges suggest a window during which the brain may be particularly vulnerable to inflammatory bystander damage.
Inhibition of Glutamate‐induced Neurotoxicity by a Tau Antisense Oligonucleotide in Primary Culture of Rat Cerebellar Granule Cells
Authors: Pizzi Marina , Valerio Alessandra , Arrighi Virginia , Galli Paola , Belloni Marco , Ribola Marina , Alberici Antonella , Spano PierFranco , Memo Maurizio
Published: April 2006

Short‐term exposure of primary cultures of cerebellar granule cells from neonatal rat brain to high concentrations of glutamate resulted in a significant increase of both immunoreactivity to and mRNA levels of tau protein. Time‐course experiments revealed the increases of tau immunoreactivity and mRNA levels to be maximal 2 h after the glutamate pulse. To investigate the relationship between newly synthesized tau protein and glutamate‐induced neurotoxicity, neurons were preincubated with a specific tau antisense oligonucleotide. This treatment resulted in (i) inhibition of the glutamate‐induced increase of tau immunoreactivity and (ii) a decrease in the sensitivity of the neurons to neurotoxic concentrations of glutamate. These data indicate that induction of the cytoskeleton‐associated tau protein participates in the cascade of events promoted by glutamate leading to neurodegeneration.
NMDA and Kainate Induce Internucleosomal DNA Cleavage Associated With Both Apoptotic and Necrotic Cell Death in the Neonatal Rat Brain
Authors: van Lookeren Campagne M. , Lucassen P. J. , Vermeulen J. P. , Balazs R.
Published: April 2006

Injection of N‐methyl‐D‐aspartate (NMDA) or kainate in the striatum of 7‐day‐old rats induced massive cell loss in the ipsilateral striatum, hippocampus and inner cortical layers. In order to examine whether apoptosis contributes to cell death in this model of excitotoxic injury we examined the progression of internucleosomal DNA fragmentation and changes in cellular ultrastructure. Agarose gel electrophoresis of DNA extracted from the ipsilateral striatum, cerebral cortex and hippocampus clearly showed breakdown of DNA into oligonucleosome‐sized fragments, indicative of apoptosis, 12 h post‐NMDA injection. In addition, an increase between 12 and 24 h was observed as well as a continuous presence 5 days later. Kainate induced a similar time course of oligonucleosomal DNA fragmentation, but the intensity of the ethidium bromide stained bands was less compared with that observed for NMDA. DNA fragmentation was not detected in animals intrastriatally injected with Tris‐HCl or in animals treated with MK‐801 [(+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohept‐5,10‐imine hydrogen maleate, 1 mg/kg] 30 min after NMDA injection. MK‐801 had no effect on DNA fragmentation induced by kainate. In addition to agarose gel electrophoresis, terminal deoxynucleotidyltransferase‐mediated dUTP‐biotin nick end labelling (TUNEL) was used for detection of DNA fragmentation in sections. A gradual increase in the density of both apoptotic and non‐apoptotic TUNEL nuclei was found in the anterior cingulate (ACC) and retrosplenial (RSC) areas of the cortex, the striatum, and the CA1 area and dentate gyrus of the hippocampus over the first 24 h post‐NMDA or kainate injection. In the contralateral hemisphere hardly any TUNEL nuclei were present and their density was comparable with that in animals injected with vehicle only. In the ipsilateral mammillary nucleus (MN), which showed no signs of acute cell swelling after intrastriatal injection with NMDA, internucleosomal DNA fragmentation was found 24 and 48 h after intrastriatal NMDA injection. Here, the density of TUNEL cells with apoptotic morphology was high at 12 and 24 h post‐NMDA injection but returned to control levels by 5 days. Electron microscopy showed cells with a clearly apoptotic morphology in the ACC and RSC and in the MN 24 h after NMDA injection. In the CA1 area of the hippocampus a necrotic, rather than an apoptotic, ultrastructure prevailed, indicating that the TUNEL method stained both apoptotic and necrotic cells. Based on biochemical and morphological criteria this study provides strong evidence that both apoptosis and necrosis are involved in NMDA‐ or kainate‐induced excitotoxic cell death in the neonatal rat brain.
Brain Structure and Task‐specific Increase in Expression of the Gene Encoding Syntaxin 1B During Learning in the Rat: A Potential Molecular Marker for Learning‐induced Synaptic Plasticity in Neural Networks
Authors: Davis S. , Rodger J. , Hicks A. , Mallet J. , Laroche S.
Published: April 2006

The mRNAs encoding the synaptic vesicle proteins syntaxin 1 B and synapsin I were measured using in situ hybridization in several brain regions‐the dentate gyrus, CA3 and CA1 of the hippocampus, the parietal, the motor and prefrontal cortices and the core and shell of the accumbens‐of rats that were learning a spatial reference or working memory task on a radial arm maze. The mRNA encoding syntaxin 1B was significantly increased in all hippocampal regions in rats learning the working memory task, whereas it was increased in the prelimbic area of the prefrontal cortex and the shell of the accumbens in rats learning the spatial reference memory task. No change in mRNA encoding syntaxin 1B was observed in the motor and parietal cortices or the core of the accumbens, and the mRNA encoding synapsin I was not significantly different from that of naive caged controls or rats running the maze for continuous reinforcement in any of the brain structures examined. These results demonstrate that the gene encoding a key member of synaptic vesicle function is up‐regulated in a task‐ and brain‐specific manner during learning. They are discussed in terms of the potential role this protein may play in trans‐synaptic propagation of plasticity within specific neural networks as a function of the information required in the laying down of different types of memory.
Two Glutamate Decarboxylase Forms Corresponding to the Mammalian GAD65 and GAD67 are Expressed During Development of the Chick Telencephalon
Authors: Åhman Anna‐Karin , Wågberg Fredrik , Mattsson Mats‐Olof
Published: April 2006

The γ‐aminobutyric acid (GABA)‐synthesizing enzyme glutamate decarboxylase (GAD) was studied during development of the chick telencephalon. By means of reverse‐phase HPLC analysis, we showed that GABA indeed accumulates during embryogenesis, whereas the levels of glutamate, the substrate for GAD, are more or less unchanged up to later developmental stages. The enzyme activity increased ∼25‐fold from embryonic day 3 to embryonic day 17. Immunoblotting data revealed that two GAD proteins, of ∼65 and 67 kDa, were present during the period investigated. Furthermore, Northern blot analysis with probes obtained from rat cDNA sequences, as well as a chicken‐specific probe for GAD65 generated by means of reverse transcriptase‐polymerase chain reaction (RT‐PCR), strengthened the interpretation that the chick embryo expresses genes corresponding to GAD65 and GAD67. The rat probes recognized transcript sizes of 3.9 kb (GAD65) and 5.6 kb (GAD67), sizes which are different from those of the rat brain (Erlander et al., Neuron, 7, 91−100, 1991). Sequencing of the RT‐PCR products revealed a high level of homology (82% at the nucleotide level) between the mammalian and chick GAD65 genes. Taken together, these findings suggest that the chick embryo expresses two GAD genes during embryogenesis. The functional properties of each gene product remain to be investigated.
Selective Depletion of Clear Synaptic Vesicles and Enhanced Quantal Transmitter Release at Frog Motor Nerve Endings Produced by Trachynilysin, a Protein Toxin Isolated from Stonefish (Synanceia trachynis) Venom
Authors: Colasante Cesare , Meunier Frédéric A. , Kreger Arnold S. , Molgó Jordi
Published: April 2006

Our previous observation that low concentrations of stonefish (Synanceia trachynis) venom elicit spontaneous quantal acetylcholine release from vertebrate motor nerve terminals prompted our present study to purify the quantal transmitter‐releasing toxin present in the venom and to characterize the toxin's ability to alter the ultrastructure and immunoreactivity of frog motor nerve terminals. Fractionation of S. trachynis venom by sequential anion exchange fast protein‐liquid chromatography (FPLC) and size‐exclusion FPLC yielded a highly purified preparation of a membrane‐perturbing (haemolytic) protein toxin, named trachynilysin. Trachynilysin (2–20 μg/ml) significantly increased spontaneous quantal acetylcholine release from motor endings, as detected by recording miniature endplate potentials from isolated frog cutaneous pectoris neuromuscular preparations. Ultrastructural analysis of nerve terminals in which quantal acetylcholine release was stimulated to exhaustion by 3 h exposure to trachynilysin revealed swelling of nerve terminals and marked depletion of small clear synaptic vesicles. However, trachynilysin did not induce a parallel depletion of large dense‐core vesicles. Large dense‐core vesicles contained calcitonin gene‐related peptide (CGRP), as revealed by colloidal gold immunostaining, and trachynilysin‐treated nerve endings exhibited CGRP‐like immunofluorescence similar to that of untreated terminals. Our results indicate that the ability of stonefish venom to elicit spontaneous quantal acetylcholine release from vertebrate motor nerve terminals is a function of trachynilysin, which selectively stimulates the release of small clear synaptic vesicles and impairs the recycling of small clear synaptic vesicles but does not affect the release of large dense‐core vesicles. Trachynilysin may be a valuable tool for use in other secretory terminals to discriminate between neurotransmitter and neuropeptide release.
Zinc Modulation of Bicuculline‐sensitive and ‐insensitive GABA Receptors in the Developing Rat Hippocampus
Authors: Martina Marco , Mozrzymas Jerzy W. , Strata Fabrizio , Cherubini Enrico
Published: April 2006

Intracellular recordings were used to study the effects of zinc on the bicuculline‐sensitive and ‐insensitive responses evoked by GABA in CA3 rat hippocampal neurons in slices obtained from postnatal day (P) 0 to P8. In the absence of bicuculline, zinc inhibited GABA‐induced responses in a concentration‐dependent manner. This effect was developmentally regulated, being maximal (50%) between P0 and P5 and then declining to 30% after P5. In the presence of bicuculline, GABA‐resistant responses were potentiated in 49% of cases, depressed in 38% and not affected in 13%. The period of maximum potentiation between P0 and P2 coincided with that of maximum expression of the bicuculline‐resistant receptors. The effects of zinc were also studied using the whole‐cell and outside‐out configuration of the patch‐clamp technique on bicuculline‐sensitive and ‐insensitive GABA‐induced currents elicited in isolated cells acutely dissociated from the same slices as those used for intracellular recordings. At a holding potential of ‐50 mV in symmetrical chloride solutions, GABA (50 and 100 μM) activated whole‐cell inward currents which were reversibly blocked by zinc. The EC50 values for the blocking effect of zinc on currents evoked by 50 and 100 μM GABA were 6.6 nM and 5.8 μM respectively. In the presence of bicuculline (100 μM), zinc potentiated the residual responses to GABA; the response curve was bell‐shaped with a peak at 1 μM. When the response to GABA was completely abolished by bicuculline, zinc (1 μM) was often able to restore it. In the presence of bicuculline, however, zinc was not able to restore the response to isoguvacine. In two excised outside‐out patches, zinc (1 μM) increased the activity of opening of bicuculline‐resistant GABA‐evoked single channel currents (Np) from 1 to 1.87 and from 0.25 to 0.42 respectively, without changing single‐channel conductance. These data suggest that down‐ or up‐regulation of bicuculline‐sensitive or ‐insensitive GABA receptors may be functionally important in regulating synaptic activity during development.