bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of Fictive Locomotion by Sulphur‐containing Amino Acids in an In Vitro Newborn Rat Preparation
Authors: Houssaini Youssef Sqalli , Cazalets Jean‐René , Martini Fabienne , Clarac François 
Published: April 2006

AbstractThe role of the sulphur‐containing amino acids (SAAs) in the initiation of fictive locomotion was tested in an isolated spinal cord preparation from newborn rats. These substances were bath‐applied and the fictive locomotion was recorded in the lumbar ventral roots. It emerged from this study that all the compounds tested could trigger an organized pattern (alternating left and right bursts of activity) with a dose‐dependent response. However, specific frequency and concentration ranges were observed with each of these SAAs. Moreover, a clear‐cut difference between d and l isomers in the ability of the SAAs to induce this activity was observed: the SAAs of the d‐forms were found to be generally more potent than those of the l‐forms. The effects of the SAAs were found to be mediated by both NMDA and non‐NMDA receptors, since they were blocked in a dose‐dependent manner by the specific antagonists of these receptors. Moreover, it was observed that β‐p‐chlorophenylglutamic acid, an uptake inhibitor of homocysteic acid (HCA), potentiated the effect of exogenously applied HCA, which supports the idea that HCA may act as a transmitter. The sulphuric and non‐sulphuric amino acids were also classified in their order of potency. The most potent compound turned out to be d‐homocysteine sulphinic acid, while d‐cysteine sulphinic acid was the least potent. It also emerged that the maximal frequencies obtained with SAAs and excitatory amino acids were in the same range, which might correspond to the maximal limits of this system.
Axotomy‐induced Changes in Ca2+ Homeostasis in Rat Sympathetic Ganglion Cells
Authors: Sánchez‐Vives Maria V. , Valdeolmillos Miguel , Martínez Salvador , Gallego Roberto 
Published: April 2006

AbstractSome of the marked biochemical and electrophysiological changes provoked by section of the axon in mature neurons suggest that the intracellular calcium concentration ([Ca2+]i) may be increased. We have measured the [Ca2+]i using the fluorescent indicator Indo‐1 microinjected into rat superior cervical ganglion neurons. No differences in resting [Ca2+]i levels were found between control neurons and cells which had been axotomized 7–10 days before. However, the rise in [Ca2+]i evoked by orthodromic or antidromic stimulation and the recovery after the stimulating train were considerably slower in axotomized neurons than in control cells. We also found that the number of calbindin‐D28k‐immunopositive cells in the ganglion increases after axotomy, which could be related to the observed differences in calcium homeostasis.
Differentiation of Transmitter Phenotypes in Rat Cerebral Cortex
Authors: Götz Magdalena , Bolz Jürgen 
Published: April 2006

AbstractCortical neurons differ in their neurochemical properties. Projection neurons use excitatory amino acids as transmitters, most local interneurons contain the inhibitory transmitter GABA, and specific subtypes of local circuit neurons express distinct neuropeptides. How this cellular diversity is generated during development is not known. We have been studying the transmitter differentiation of cortical neurons in different in vitro systems using immunohistochemical techniques. Transmitter phenotypes of cortical neurons were examined in slice cultures, i.e. in the absence of extrinsic cortical connections, and in dissociated cortical cell cultures, i.e. in the absence of extrinsic and intrinsic cortical connections. The expression of vasoactive intestinal polypeptide in cortical interneurons occurred normally in slice cultures prepared from neonatal rats between birth and 2 days of age, but was strongly impaired in dissociated cell cultures prepared at the same time. These results suggest that the intact cortical environment present in the slice cultures exerts crucial influences for neuropeptide differentiation. In contrast, the transmitters glutamate and GABA were expressed normally in the appropriate cell types and similar in proportions in dissociated cell cultures prepared from cortices at embryonic day 19. Only cells dissociated during S‐phase failed to express glutamate and GABA in vitro. When cells were kept for 24 h after mitosis in a cortical slice preparation in vitro, however, they later expressed their appropriate transmitter phenotypes. Thus, signals from the local cortical environment that act early in the cell cycle are required for the specification of transmitter phenotypes of cortical neurons.
Purinergic Modulation of the Evoked Release of [3H]Acetylcholine from the Hippocampus and Cerebral Cortex of the Rat: Role of the Ectonucleotidases
Authors: Cunha Rodrigo A. , Ribeiro J. A. , Sebastião A. M. 
Published: April 2006

AbstractModulation by exogenous and endogenous adenine nucleotides and adenosine of [3H]acetylcholine release evoked by veratridine (10 μM) was compared in synaptosomal fractions from the hippocampus and the cerebral cortex of the rat. In both brain areas, exogenously added ATP or adenosine (10–100 μM) inhibited the evoked tritium release. In the hippocampus, ATPμS, an ATP analogue more resistant to catabolism than ATP, was virtually devoid of effect on tritium release, and the effect of ATP was prevented by the ecto‐5′‐nucleotidase inhibitor α,β‐methylene ADP (100 μM), by adenosine deaminase (2 U/ml) and by the A1 adenosine receptor antagonist 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX, 20 nM). In contrast, in the cerebral cortex, the effect of ATP on tritium release was not prevented by either α,β‐methylene ADP (100 μM) or adenosine deaminase (2 U/ml), and several ATP analogues (30 μM) inhibited release. The order of intensity of the inhibitory effects of the ATP analogues was: ATPγS > ATP > ñ,γ‐imido ATP > β,γ‐methylene ATP > 2‐methyl‐S‐ATP, α,β‐methylene ATP. The effect of ATPγS in the cerebral cortex was prevented by DPCPX (20 nM) and was not affected by the P2 purinoceptor antagonist suramin (100 μM). In the hippocampus, α,β‐methylene ADP (100 μM) increased the evoked release of tritium, and adenosine deaminase (2 U/ml) produced an even greater increase; when adenosine deaminase was added in the presence of α,β‐methylene ADP, adenosine deaminase still increased the evoked release of tritium. In the cerebral cortex, DPCPX (20 nM) and adenosine deaminase (2 U/ml) increased the evoked tritium release by a similar magnitude, but the effect of adenosine deaminase was smaller than in the hippocampus. It is concluded that in the cerebral cortex ATP as such presynaptically inhibits acetylcholine release, whereas in the hippocampus the role of adenine nucleotides is as a source of endogenous extracellular adenosine that tonically inhibits acetylcholine release. The results also show that besides formation of adenosine from adenine nucleotides, released adenosine as such contributes in nearly equal amounts to the pool of endogenous adenosine that presynaptically inhibits acetylcholine release in the hippocampus.
Differential Localization and pH Dependency of Phosphoinositide 1,4,5‐IP3, 1,3,4,5‐IP4 and IP6 Receptors in Rat and Human Brains
Authors: Parent Angèle , Quirion Rémi 
Published: April 2006

AbstractIt is well established that the inositol lipids mediate signal transduction in several cellular populations. Many neurotransmitters, hormones and growth factors act at plasma membrane receptors to induce the hydrolysis of phosphatidylinositols and hence the generation of various inositol phosphates (IP). The best known member of this family is 1,4,5‐IP3, which is associated with the release of Ca2+ from intracellular pools. It has also been proposed that two others inositides, 1,3,4,5‐IP4 and IP6, may be involved in Ca2+ homeostasis. In order to study the possible relevance of these various inositides in neuronal tissues, we have localized the respective receptors in rat and human brain under both acidic and basic pH conditions. In the hippocampal formation, [3H]1,3,4,5‐IP4 binding sites are concentrated in the hilus and the molecular layer while a clearly different pattern of distribution is seen for [3H]1,4,5‐IP3, its highest concentration of labelling being concentrated in the oriens and radiatum laminae. This contrasting profile of distribution is also observed in other brain areas such as the caudate‐putamen, the septo‐hippocampal area, and the molecular and granular layers of the cerebellum. Moreover, while highest amounts of specific [3H]1,4,5‐IP3 binding are obtained at pH 8.5, the opposite is found for [3H]1,3,4,5‐IP4, with high binding levels seen under acidic conditions. [3H]IP6 binding sites are broadly distributed with specific labelling concentrated in areas enriched with neuronal perikarya such as the granular cell layer of the dentate gyrus, the pyramidal cell layers of the hippocampus and the granular cell layer of the cerebellum. [3H]IP6 binding is particularly abundant at basic pH in a few regions such as the accessory olfactory bulb, the piriform cortex and the septo‐hippocampal nucleus. The pH dependency of each inositide binding may be correlated to changes in intracellular pH that are observed following the activation of phospholipase C. The apparent distribution of specific 1,4,5‐IP3, 1,3,4,5‐IP4 and IP6 binding sites is rather similar in rat and human brains, suggesting their preserved functions across these two species.
Neonatal Sciatic Nerve Section Results in a Rearrangement of the Central Terminals of Saphenous and Axotomized Sciatic Nerve Afferents in the Dorsal Horn of the Spinal Cord of the Adult Rat
Authors: Shortland Peter , Fitzgerald Maria 
Published: April 2006

AbstractPrevious studies have shown that following neonatal peripheral nerve injury, adjacent intact myelinated and unmyelinated primary afferents sprout into the central denervated terminal area. The present study investigates this in more detail and goes further, to study the fate of the central terminals of the surviving axotomized primary afferent neurons. Bulk labelling of the sciatic and saphenous nerves with horseradish peroxidase conjugated to choleragenoid (B‐HRP), to label the A fibres, or wheatgerm agglutinin (WGA‐HRP), to label C fibres were employed to investigate the central consequences of sciatic nerve section and ligation on the day of birth, in adult rats. Bulk labelling of the axotomized sciatic or intact saphenous nerve with either tracer and comparison with contralateral controls revealed alterations to the terminal field. The intact saphenous nerve terminal field expanded caudally from mid L4 to the L4‐L5 boundary when labelled with WGA‐HRP and to the sacral cord when labelled with B‐HRP. Labelling the axotomized sciatic nerve with either tracer revealed little change in the overall somatotopic organization of central terminals, although labelling was less intense compared to control nerves and more variable with WGA‐HRP. Invasion of the substantia gelatinosa (SG) by axotomized A fibres was observed in segments L3‐5, into the area occupied by axotomized C fibres. This area was also invaded by intact saphenous A fibres in the L4–5 segments. These results demonstrate that following neonatal nerve section: (i) axotomized primary afferents are able to retain a ‘normal’ somatotopic map in the rostrocaudal plane; (ii) both A and C fibres from adjacent intact nerves sprout into the denervated territory, but A fibres sprout further caudally; (iii) axotomized A fibres and invading intact A fibres both sprout dorsally into denervated SG. As a result, there is considerable overlap between nerve territories in denervated spinal cord, suggesting that competition for laminar termination sites exists between A and C fibres and also between axotomized and intact primary afferents.
Localization of Oxytocin Binding Sites in the Thoracic and Upper Lumbar Spinal Cord of the Adult and Postnatal Rat: A Histoautoradiographic Study
Authors: Reiter M. K. , Kremarik P. , Freund‐Mercier M. J. , Stoeckel M. E. , Desaulles E. , Feltz P. 
Published: April 2006

AbstractOxytocin binding sites were detected by autoradiography on films and emulsion‐coated sections in the spinal cord of adult and postnatal rats from C8 to L2, using a highly selective 125l‐labelled oxytocin antagonist. Oxytocin binding sites were detected on all transverse sections in the dorsal horn, where labelling was scattered over laminae I and II. The autonomic areas, i.e. the intermediolateral cell column, the central grey (lamina X) and the nucleus intercalatus were labelled. Binding in the intermediolateral cell column was most frequently observed on sections from T9 to T11 in adult and T7 to T8 in postnatal rats. In this location, oxytocin binding sites were highly concentrated on cell bodies of putative sympathetic preganglionic neurons; however, not all of these cells were labelled. Diffuse labelling occurred on the dorsal part of the central grey, mainly between T8 and L2. Isolated labelled cells belonging to the nucleus intercalatus were scattered between the central canal and the intermediolateral cell column. In addition, oxytocin binding sites were found on some motoneurons of the lateral group of T12‐T13, but only in postnatal rats. The distribution of oxytocin binding sites in the rat spinal cord coincides with that of the oxytocin innervation and strongly suggests a modulatory role of this peptide in sensory and autonomic functions.
Rapid Desensitization of the Metabotropic Glutamate Receptor that Facilitates Glutamate Release in Rat Cerebrocortical Nerve Terminals
Authors: Herrero I. , Miras‐Portugal M. T. , Sánchez‐Prieto J. 
Published: April 2006

AbstractThe metabotropic autoreceptor of glutamatergic nerve terminals from the cerebral cortex of adult rats has been characterized. Receptor activation involves a rapid and transient increase in diacylglycerol, which is sensitive to l‐2‐amino‐3‐phosphonopropionate (l‐AP3) and l‐2‐amino‐4‐phosphonobutanoic acid (l‐AP4) and is partially blocked by pertussis toxin. Protein kinase C (PKC) has a negative feedback control in this transduction pathway because the activation of the kinase, either by phorbol esters or by the endogenous diacylglycerol produced by the receptor, results in a reversible receptor desensitization, with loss of the ability to further facilitate glutamate release. It is concluded that the facilitatory metabotropic receptor located at the glutamatergic nerve endings belongs to the subclass coupled to phosphoinositide hydrolysis and that the rapid and use‐dependent desensitization of the facilitatory pathway may underlie a mechanism to prevent its permanent activation and thereby to avoid neurotoxicity.
Embryonic Purkinje Cells Grafted on the Surface of the Adult Uninjured Rat Cerebellum Migrate in the Host Parenchyma and Induce Sprouting of Intact Climbing Fibres
Authors: Rossi Ferdinando , Borsello Tiziana , Strata Piergiorgio 
Published: April 2006

AbstractBy grafting solid pieces of cerebellar anlage onto the surface of the adult rat cerebellum, we have investigated the problem of the interactions between embryonic and adult neurons in an intact brain. A few days after grafting, embryonic astrocytic processes crossed the graft‐host interface and radiated into the recipient molecular layer. Several grafted Purkinje cells also migrated into the host brain along such processes as well as adult Bergmann glia. Adult climbing fibres, labelled by means of Phaseolus vulgaris leucoagglutinin (PHA‐L), sprouted new collateral branches which terminated on embryonic Purkinje cells at both extra‐ and intraparenchymal levels. No sign of activation of host astroglia or microglia was evident in the host cerebellum in relation to these processes. Embryonic Purkinje cells which migrated into the host cerebellum developed an adult‐like morphology. Intraparenchymal grafts of neocortical embryonic tissue induced conspicuous growth of host olivary axons, characterized by a pattern which was different from that observed following cerebellar grafts. By contrast, when neocortical tissue was placed onto the surface of the recipient cerebellum, graft‐host interactions were limited and climbing fibre sprouting was rarely seen. These results show that (i) supernumerary Purkinje cells can penetrate and settle in the adult intact cerebellar cortex, (ii) adult climbing fibres are able to innervate these new targets in the absence of any injury or activation of non‐neuronal cells of the adult brain, and (iii) in the absence of damage to the adult brain, the plasticity of adult olivary axons is specifically elicited and controlled by embryonic Purkinje cells.
A PET Study of Somatosensory Discrimination in Man. Microgeometry Versus Macrogeometry
Authors: O'Sullivan Brendan T. , Roland Per E. , Kawashima Ryuta 
Published: April 2006

AbstractThe regional cerebral blood flow (rCBF) was measured with 15O‐butanol and positron emission tomography (PET) in 10 healthy subjects in order to compare cerebral activation involved in the somatosensory discrimination of microgeometric features with cerebral activation associated with the discrimination of macrogeometric features. Subjects performed two‐alternative forced choice (2‐AFC) discriminations of pairs of stimuli from a series of quantified standardized stimuli that differed in roughness (microgeometry), and a separate 2‐AFC task of smooth tactile stimuli that differed in length (macrogeometry). Results are presented from three conditions: (1) a roughness discrimination task; (2) a length discrimination task; and (3) a control trial in which subjects were required to reproduce similar exploratory finger movements only, but without a specific stimulus to feel. Mean subtraction images were computed using the computerized adjustable brain atlas of Greitz et al. (1991, J. Comput. Assisted Tomogr., 15, 26–38) and areas of significant blood flow change were identified. Both the roughness and the length discrimination tasks activated overlapping cortical fields contralaterally in the anterior and posterior lip of the postcentral sulcus. However, in the length discrimination, activation of the posterior lip of the postcentral sulcus extended deeper into the sulcus and there was also a separate additional area of activation in the anterior part of the precentral gyrus. Furthermore, the length discrimination task activated fields in the overt part of the supramarginal gyrus bilaterally as well as fields in the angular gyrus bilaterally. Thus roughness discrimination uses only a subset of the cortical regions that are needed for the recovery of length information, which requires more extensive somatosensory processing. This finding may be partly explained in that length perception needs both edge detection of the stimuli used, as well as integrated information of surface length and velocity, which is not necessary for roughness perception. Specific differences in the acquisition of necessary tactile information between the two discrimination tasks was reflected in different sampling strategies.
Auditory Localization Behaviour in Visually Deprived Cats
Authors: Rauschecker Josef P. , Kniepert Ulla 
Published: April 2006

AbstractThe ability to localize sounds in azimuth was tested in five cats that had been binocularly deprived of vision from birth for several months and in three normal age‐matched controls. Brief tone bursts were presented in an eight‐choice apparatus along 360° of the azimuthal plane at constant elevation. Using positive reinforcement techniques, the cats were trained to walk from the centre of the 3 m diameter circular enclosure to the hidden loudspeakers. The distribution of sound localization error from 55 trials per cat at each speaker position was measured, and its standard deviation was used to assess the precision of sound localization. All cats localized tones straight ahead of them most precisely; performance at lateral and rear positions was gradually less precise. When the sound localization ability of normal and binocularly deprived cats was compared across speakers, a significantly enhanced precision was found for binocularly deprived cats overall (P < 0.002; two‐way analysis of variance). An improvement was found at each individual speaker position, but it was greatest at lateral and rear positions. In two sets of control experiments normal cats were retested (i) in the dark with the aid of an infrared camera and (ii) after 3 months of binocular lid suture. Normal cats in the dark did not show any differences in their sound localization behaviour. Late‐deprived cats showed a tendency for better performance, which fell short of statistical significance. Our results in visually deprived cats agree well with some reports on the sound localization ability of blind humans, but disagree with others. Our data provide support for a hypothesis of compensatory plasticity, in which sensory functions get sharpened with the loss of another modality. They seem to rule out the necessity for vision to play a role in the postnatal calibration of auditory space.
Pattern of Development of the Callosal Transfer of Visual Information to Cortical Areas 17 and 18 in the Cat
Authors: Milleret C. , Houzel J. C. , Buser P. 
Published: April 2006

AbstractThe aim of this study was to investigate the development of visual callosal transfer in the normally reared cat. Two‐ to nine‐week‐old kittens and adults (used as controls) underwent section of the optic chiasm. Three days later, the animals were placed under anaesthesia and paralysed; unit activities were recorded from visual cortical areas 17 and 18 and from the white matter in one hemisphere. The units were tested for their responses to visual stimulation of each eye successively. Out of 1036 recorded neurons, 185 could be activated through the eye contralateral to the explored cortex via callosal transfer. Most of them could also be driven through the ipsilateral eye via the ‘direct’ geniculo‐cortical pathway. For animals aged ≤2 weeks, virtually all of these units were located at the 17/18 border zone, with a majority in the supragranular layers. When activated through the corpus callosum, they displayed receptive fields located either on the central vertical meridian of the visual field or in the hemifield ipsilateral to the explored cortex. Such extension into the ipsilateral hemifield as well as receptive field disparities of binocular units decreased with age, while spontaneous activity, strength of response, orientation selectivity and ability to respond to slits moving at middle‐range velocity increased. The main conclusion is that the transient callosal projections described by anatomists, which are present until 3 months of age, do not achieve supraliminar synaptic contacts with parts of areas 17 and 18 other than the 17/18 border zone, at least from 12 days after birth. However the visual callosal transfer in young animals displays some characteristics which disappear with age.
Expression of Soluble Guanylyl Cyclase Gene in Adult Rat Brain
Authors: Burgunder J.‐M. , Cheung P. T. 
Published: April 2006

AbstractThe synthesis of the intracellular messenger, cyclic GMP, is catalysed by particulate or soluble guanylyl cyclase (sGCY). sGCY is activated by nitric oxide, a compound with putative neurotransmitter functions, especially in long‐term potentiation. Hybridization histochemistry with a probe complementary to the rat lung large (α1) subunit was used to assess the exact localization of sGCY mRNA in the rat brain. Many cells in the olfactory bulb contained sGCY mRNA. In the whole cerebral cortex, sGCY mRNA was found in all layers, with a predominance in layers II ‐ III. A similar pattern was found in the olfactory tuberculum, in continuation with the piriform cortex and the cortical amygdaloid nucleus. All parts of the striatum expressed sGCY mRNA. sGCY mRNA was also found in the habenula medialis, in the pinealis in some diencephalic nuclei, and in the granule cell layers of the cerebellum. This study provides a description of the normal anatomy of sGCY gene expression in the rat forebrain as a basis for the study of the modulation of expression after physiological and pharmacological manipulations.