bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurotensin‐like Peptides in the CNS of Lampreys: Chromatographic Characterization and Immunohistochemical Localization with Reference to Aminergic Markers
Authors: Brodin Lennart , Theordorsson Elvar , Christenson Johan , Cullheim Staffan , Hökfelt Tomas , Brown John C. , Buchan Alison , Panula Pertti , Verhofstad Albert A. J. , Goldstein Menek 
Published: April 2006

AbstractNeurotensin (NT)‐like peptides in the CNS of the lamprey Lampetra fluviatilis were studied by radioimmunoassay (C‐terminal specific NT antiserum), reverse‐phase HPLC and immunohistochemistry. Multiple peaks of NT‐immunoreactive (‐ir) material were observed upon HPLC, of which a major peak eluted in the position of bovine NT. Immunofluorescence histochemistry showed that a monoclonal antibody recognizing the N‐terminal (1–11) fragment of NT, as well as two polyclonal NT antisera labelled a large number of cell bodies in the periventricular area of hypothalamus, including the postinfundibular commissural nucleus and the ventral and dorsal hypothalamic nuclei. Additional groups of NT‐ir cells were observed in the preoptic nucleus, the postoptic commissural nucleus, the mesencephalic tegmentum (L.fluviatilis), and in the spinal cord (L.fluviatilis and Ichtyomyzon unicuspis). Dense NT‐ir fibre plexuses were present in the caudal hypothalamus, corpus striatum, ventral mesencephalon, and in the dorsal horn and lateral margin of the spinal cord. At the ultrastructural level the lateral spinal margin showed NT‐ir terminal structures, which in most cases were not associated with synaptic specializations, although occasional synaptic contacts with unlabelled elements were found. The relation between NT‐ir and monoamine‐containing cells was examined with immunofluorescence double‐staining, using antisera to tyrosine hydroxylase (TH), 5‐hydroxytryptamine (5‐HT), and histamine respectively. In the periventricular nuclei of hypothalamus numerous TH‐, 5‐HT‐, as well as histamine‐ir cells were located in close association with NT‐ir cells, but none of the aminergic markers could be detected within NT‐ir neurons. The chemical properties as well as the anatomical distribution of lamprey NT‐like peptides show several similarities with those present in mammals, suggesting that NT‐containing neuronal systems in the CNS developed early in vertebrate phylogeny.
Mutual Re‐excitation with Post‐Inhibitory Rebound: A Simulation Study on the Mechanisms for Locomotor Rhythm Generation in the Spinal Cord of Xenopus Embryos
Authors: Roberts Alan , Tunstall M. J. 
Published: April 2006

AbstractWe have used computer simulations as one way to test the hypothesis that locomotor rhythm production for swimming in frog embryo spinal cord depends on rebound from inhibition and is sustained by mutual re‐excitation among spinal excitatory interneurons. All simulations were based on physiological and anatomical data on the neurons and circuitry of Xenopus embryo spinal cord.Model ‘neurons’ had resistively coupled axon, soma, and dendrite compartments. Membrane properties were based on Hodgkin‐Huxley equations with resting potential at −75 mV and where soma and dendrite had reduced K+ and Na+ conductance and slowed K+ conductance. These ‘neurons’ fired a single non‐overshooting spike both to depolarizing current and afer hyperpolarizing current given during imposed depolarization. Synapses were made on to the dendrite. Inhibitory and excitatory synaptic channels had Nernst potentials of ‐80 and 0 mV, time constants for opening of 1 ms, and closing of 6 and 75 ms. When the short inhibitory postsynaptic potential occurred on the long (N‐methyl‐D‐aspartate‐type) excitatory postsynaptic potential, it led to rebound firing.A four ‘neuron’ symmetrical network was built with reciprocal inhibition and where excitatory ‘neurons’ re‐excited themselves and the inhibitory ‘neuron’ on their own side. The rhythmic alternating activity with one spike per cycle produced reliably by this network was self‐sustaining, initiated by a brief synaptic input, and closely resembled the spinal cord motor pattern during swimming. The robustness of this activity pattern was investigated by varying cellular and synaptic parameters, initiating inputs, and network connectivity. We conclude that cellular, synaptic, and network properties are all important and that mutual re‐excitation, a form of positive feedback, could sustain motor rhythm production in the Xenopus embryo spinal cord.
Galanin and Glibenclamide Modulate the Anoxic Release of Glutamate in Rat CA3 Hippocampal Neurons
Authors: Ben‐Ari Y. 
Published: April 2006

AbstractThe effects of brief anoxic episodes on intracellularly recorded CA3 pyramidal neurons have been studied in the hippocampal slice preparation. Anoxia induced a depolarization occasionally preceded by a transient hyperpolarization associated with a fall in input resistance. The anoxic depolarization was due to the release of glutamate from presynaptic terminals since it was blocked by tetrodotoxin (TTX) (1 μM) or by the broad spectrum excitatory amino acid antagonist kynurenate (1 mM). In the presence of TTX (1 μM) or kynurenate (1 mM), anoxia only induced a hyperpolarization which was due to activation of a K+ conductance. The anoxic depolarization was blocked by galanin, a hormone which activates ATP sensitive K+ (K + ATP) channels. Anoxic depolarization was increased by the potent sulfonylurea agent glibenclamide (GLIB) which blocks K + ATP channels. Bath applications of these agents had little effect when applied in oxygenated Krebs solution suggesting that their action may be mediated by K + ATP channels. Since excessive release of glutamate during anoxia is neurotoxic, agents such as galanin which activate K + ATP channels may provide tissue specific protection against anoxic damage.
Regulation of Nerve Growth Factor (NGF) Synthesis in the Rat Central Nervous System: Comparison between the Effects of Interleukin‐1 and Various Growth Factors in Astrocyte Cultures and in vivo
Authors: Spranger Matthias , Lindholm Dan , Bandtlow Christine , Heumann Rolf , Gnahn Hannes , Näher‐Noé Martina , Thoenen Hans 
Published: April 2006

AbstractIn order to obtain information on the physiological regulation of NGF‐synthesis in the central nervous system (CNS) we investigated the effects of a series of growth factors (known to be present in the CNS) in cultures of purified rat astrocytes and compared these effects with those observed after intraventricular injection of the same molecules. After preliminary experiments had shown that 10% fetal calf serum (FCS) produced a marked increase in NGF‐mRNA levels in astrocytes (but neither in microglia nor oligodendrocytes) as demonstrated by Northern blot analysis and in situ hybridization the experiments were performed at low (0.5%) FCS concentrations. Supramaximal concentrations of IL‐1 and various growth factors caused a 5‐ to 7‐fold increase in NGF‐mRNA after 6 h. By 24 h the NGF‐mRNA levels approached control values again, most probably due to inactivation of the added factors since after readdition after 24 h the response was about the same as the initial one. Norepinephrine and 8‐bromo‐cAMP did not change NGF‐mRNA levels. The growth factor‐mediated changes in NGF‐mRNA levels in astrocyte cultures were not consistently reflected by the changes observed after intraventricular injection. IL‐1 produced by far the largest increase in hippocampal NGF‐mRNA after intraventricular injection. This large response to IL‐1 could result from a positive feedback mechanism, since IL‐1β injection not only increases NGF‐mRNA but also IL‐1β‐mRNA in the hippocampus. The understanding of the physiological regulation of NGF synthesis in the CNS is the basis for a rational approach to its pharmacological modification. This, in turn, is an attractive alternative to the (long‐term) infusion of NGF or the transplantation of NGF‐secreting cells with the goal of providing trophic support to the cholinergic neurons of the basal forebrain nuclei. These neurons are consistently affected in the early stages of Alzheimer's disease, their impaired function being essentially responsible for the cognitive deficits.
Behavioural Effect of Engineered Cells that Synthesize L‐DOPA or Dopamine after Grafting into the Rat Neostriatum
Authors: Horellou Philippe , Marlier Lionel , Privat Alain , Mallet Jacques 
Published: April 2006

AbstractCell lines in which tyrosine hydroxylase was introduced either by infection or transfection were used in grafting experiments in a rat model of Parkinson's disease obtained by unilateral lesion of the substantia nigra. A neuroblastoma NS20 Y cell line which synthesizes only L‐DOPA and a neuroendocrine AtT‐20 cell line which produces dopamine were obtained. They were grafted into denervated striata and their ability to compensate for the dopaminergic deficit was studied. Both modified cell types displayed a rapid partial reversal of apomorphine‐induced turning behaviour. No effect was observed with the control unmodified cell lines. We discuss the usefulness of engineered cell lines to address the fundamental issues in grafting experiments and more particularly in the therapy of Parkinson's disease.
Steroid Modulation of Muscarinic Cholinergic and α2‐Adrenergic Receptor Density in the Nucleus Intercollicularis of the Japanese Quail
Authors: Ball Gregory F. , Balthazart Jacques 
Published: April 2006

AbstractAndrogen modulation of neurotransmitter receptor density was investigated in the nucleus intercollicularis (ICo) of male and female Japanese quail (Coturnix coturnix japonica). ICo appears to play an important role in the neural control of testosterone (T) dependent vocal behaviour. Two receptor types were investigated in this nucleus; muscarinic cholinergic receptors, labelled using [3H]N‐methyl scopolamine (NMS) as the ligand, and α2‐adrenergic receptors, labelled using [3H]p‐amino‐clonidine (PAC) as the ligand. Changes in receptor density were assessed using in vitro quantitative autoradiography to ensure a high degree of anatomical specificity in the identification of any steroid effects. Gonadectomy was found to reduce the density of both [3H]PAC bindings sites and [3H]NMS in specific subregions of ICo. Gonadectomized animals treated with T had levels of receptor density similar to intact birds. However, the location within ICo of the effects of T was different for each ligand. [3H]NMS binding was modulated only in a rostral subregion of the nucleus while changes in [3H]PAC receptor density were found in the medial and lateral parts of ICo at a more caudal level. These changes in receptor density parallel changes in crowing frequency that are known to occur in males and females following castration and T treatment. The receptor systems may constitute a part of the neurochemical mechanism regulating vocal behaviour.
Glutamine Synthetase is Expressed by Primary Sensory Neurons from Chick Embryos In Vitro but not In Vivo: Influence of Skeletal Muscle Extract
Authors: Barakat‐Walter I. , Droz B. 
Published: April 2006

AbstractGlutamine synthetase (GS) catalyses the ATP‐dependent formation of glutamine from glutamate and ammonia. To determine whether dorsal root ganglion (DRG) cells from chick embryos express the enzyme in vivo or in vitro, GS was detected by immunocytochemical reaction either in vibratome sections of DRG or in dissociated DRG cell cultures. The immunocytochemical detection of GS showed that in vivo the DRG taken from chick embryos at day 10 (E10), E14, E18 or from chickens after hatching were free of any GS‐positive ganglion cells; in contrast, in neuron‐enriched cultures of DRG cells grown in vitro at E10, virtually all the neuronal cells (98.6±1.0%) express GS at 3, 5 or 7 days of culture. In mixed DRG cell cultures, only 83.6±4.6% of the neurons displayed a GS‐immunoreactivity. In both culture conditions, neither the presence of horse serum nor the age of the culture appeared to affect the percentage of neurons which displayed a GS‐immunoreactivity. After [3H]glutamine uptake, radioautographs revealed that only 80% of the neurons were labelled in neuron‐enriched DRG cell cultures while 96% of the neurons were radioactive in mixed DRG cell cultures. Furthermore the most heavily [3H]glutamine‐labelled neurons were exclusively found in mixed DRG cell cultures. Combination of both immunocytochemical detection of GS and radioautography after [3H]glutamine uptake showed that strongly GS‐immunostained neurons corresponded to poorly radioactive ones and vice versa. When skeletal muscle extract (ME) was added to DRG cell cultures, the number of GS‐positive neurons was reduced to 77.5±2.5% in neuron‐enriched cultures or to 43.6±3.8% in mixed DRG cell cultures; in both types of culture, the intensity of the neuronal immunostaining was depressed. Furthermore, combined action of ME and non‐neuronal cells potentiates the enzyme repression exerted separately by ME or non‐neuronal cells. Since GS‐immunoreactivity is expressed in DRG cells grown in vitro, but not in vivo, it is suggested that microenvironmental factors influence the expression of GS. More specifically, the repression of GS by primary sensory neurons grown in vitro may be strongly induced by soluble factors present in skeletal muscle, and to a lesser extent in brain, and potentiated by non‐neuronal cells.
The Importance of Graft Placement and Task Complexity for Transplant‐Induced Recovery of Simple and Complex Sensorimotor Deficits in Dopamine Denervated Rats
Authors: Mandel Ronald J. , Brundin Patrik , Björklund Anders 
Published: April 2006

AbstractThe present study examined the role of graft placement and behavioural task complexity in determining the functional efficacy of intrastriatal grafts of dopamine‐rich fetal ventral mesencephalon (VM) placed in the dopamine (DA) depleted striatum. The functional effects of two different striatal placements of VM grafts were evaluated using tests of drug‐induced motor asymmetry, simple sensorimolor orienting response, and a more complex sensorimotor integrative task (disengage behaviour), in which the rat has to perform the orienting response while in the act of eating. Rats with complete unilateral 6‐hydroxydopamine (6‐OHDA) lesions of the mesostriatal DA pathway, received either implants of dissociated fetal VM in the central or ventrolateral portions of the denervated striatum. Nongrafted lesioned rats served as controls. Nine weeks after grafting, the rats were tested on separate days for disengage behaviour, sensorimotor orientation, and amphetamine‐induced rotational behaviour. Consistent with previous findings, the two graft placements had differential effects on drug‐induced motor asymmetry and sensorimotor responses: the centrally placed VM grafts reversed amphetamine‐induced rotational asymmetry but had little effect on the sensorimotor deficit, whereas the ventrolaterally placed grafts reversed the sensorimotor orientation deficits without any effect on the drug‐induced rotation. In contrast, fetal VM grafts, regardless of their placement, did not ameliorate the observed deficits in disengage behaviour; that is the grafted rats that had recovered their sensorimotor response in the absence of food were unable to perform the same orienting response while eating. These results provide evidence that functional intrastriatal VM grafts which are capable of restoring sensorimotor responses or motor asymmetry fail to affect lesion‐induced deficits in a task that requires more complex sensorimotor integration. It is suggested that the degree of anatomical integration of the grafted DA neurons into the host circuitry will determine the efficacy of the grafts to influence more complex sensorimotor integrative deficits in the DA lesion model.
Gamma‐Aminobutyric Acid‐Inhibitory Motor Innervation of Leg Muscles of the Shore Crab
Authors: Bévengut Michelle , Cournil Isabelle 
Published: April 2006

AbstractThe inhibitory motor innervation of a crustacean leg was studied in the crab, Carcinus maenas. In in vitro preparations of the central nervous system and the proximal leg nerves, motor nerve recordings demonstrate the presence of a single common inhibitory motor neuron which elicits picrotoxin‐sensitive inhibitory junction potentials in a distal leg muscle, the accessory flexor. This inhibitor is the common inhibitor (CI). Immunohistochemical detection of the inhibitory motor neuron neurotransmitter, gamma‐aminobutyric acid (GABA), allows us to identify three immunoreactive motor neuron axons in sections of the distal leg nerves and of proximal leg nerves. One corresponds to the CI whereas the other two are the specific inhibitors, one to the stretcher and one to the opener muscles. After nickel chloride backfills of the CI in proximal leg nerves, GABA immunodetection fails and thus confirms that CI is the single inhibitor having branches in proximal leg nerves.These results demonstrate that the inhibitory motor innervation of a crab leg comprises three and only three inhibitors: the common inhibitor innervating all leg muscles and the two specific inhibitors, each innervating a single distal leg muscle. Further conclusions can be drawn: first, a muscle innervated by more than one excitatory axon has no specific inhibitor; second, sensory afferents are not mediated by GABA. Finally, during locomotion, the leg muscles receive two very distinct types of motor input: (1) one common to all the muscles coming from the common inhibitor which was previously shown by other authors to prevent build‐up of tension in the muscles, thus allowing each muscle to contract according to (2) the specific motor input it receives from its own excitors.
Two Monoclonal Antibodies Recognizing Carbohydrate Epitopes on Neural Adhesion Molecules Interfere with Cell Interactions
Authors: Fahrig Thomas , Schmitz Brigitte , Weber Dieter , Kücherer‐Ehret Andrea , Faissner Andreas , Schachner Melitta 
Published: April 2006

AbstractWe have studied two monoclonal antibodies raised against crude fractions of membrane glycoproteins from adult mouse brain and found them to react with two carbohydrate epitopes expressed on several neural cell adhesion molecules. Other identified and unidentified glycoproteins from different cell types, organs and species were also recognized by these antibodies. Both epitopes are N‐glycosidically linked mannosidic or hybrid type oligosaccharides and co‐expressed on all the glycoproteins so far tested. In spite of their remarkable similarities, the glycan epitopes are different as shown by ELISA competition assays. In microexplant outgrowth and cell adhesion assays, both antibodies interfere with neural cell adhesion, migration, and neurite outgrowth. These observations, together with previous studies on the L2/HNK‐1 glycan (Künemund et al., 1988), indicate that adhesion molecules carry various carbohydrate epitopes mediating different cell interactions in in vitro assays.
Spontaneous Activity as a Determinant of Axonal Connections
Authors: Cook Jeremy E. , Becker David L. 
Published: April 2006

AbstractTo investigate the role of spontaneous retinal activity in map refinement, we studied goldfish kept in darkness during regeneration of a cut optic nerve. In one experiment, such fish (with lenses ablated to blur vision) were maintained for 70 days in stroboscopic light, diurnal light, or total darkness interrupted daily by 15 minutes of stroboscopic light. The retinotectal projection was then assessed for retinotopy by standard methods, using retrograde transport of wheat germ agglutinin—horseradish peroxidase. As in previous work, significantly more refinement was found in diurnal than in stroboscopic light. In darkness, refinement was as complete as in diurnal light. In a second experiment, similar fish were kept in stroboscopic light for 63 days. Some were then assessed to confirm that refinement had been delayed, while others were transferred to darkness or diurnal light for assessment later. After 7 days in either environment, no further refinement was seen; but after 21 days, substantial and significant refinement has occurred in both. Thus the effects of darkness and diurnal light were indistinguishable, and very different from those of stroboscopic light and (in previous studies) tetrodotoxin. Map refinement is evidently activity‐dependent but not experience‐dependent, and can effectively use the correlated spontaneous firing of neighbouring ganglion cells as its basis. Locally correlated spontaneous activity, which appears also to drive eye‐ and class‐specific axon segregation in mammals, occurs widely in the nervous system. It could potentially generate systematic interconnection patterns even between neuronal populations without an overtly topographic organization.
Cortical Regulation of Striatal Neuropeptide Y (NPY)‐Containing Neurons in the Rat
Authors: Kerkerian L. , Salin P. , Nieoullon A. 
Published: April 2006

AbstractThis study examined the functional relationships established by nigral, cortical, and thalamic striatal afferent pathways with neuropeptide Y (NPY)‐containing neurons in the rat rostral striatum by coupling selective deafferentation procedures and NPY immunohistochemistry. Previous experiments have shown that after unilateral 6‐hydroxydopamine (6‐OHDA)‐induced degeneration of nigrostriatal dopaminergic neurons, the mean number of NPY‐immunoreactive (lr) neurons per frontal section was increased in the striatum ipsilateral to the lesion side and unaltered in the contralateral striatum. The present topographical analysis of the 6‐OHDA lesion effects led us to state that the increase in NPY‐lr neuron density occurs in restricted ventral and medial zones of the ipsilateral striatum. Unilateral ablation of the frontoparietal cerebral cortex by thermocoagulation was moreover shown to elicit, 20–30 days later, a significant bilateral increase in the number of striatal NPY‐lr cells. The increase was more marked in the striatum ipsilateral to the hemidecortication where it was similar in amplitude to that induced by the 6‐OHDA lesion. The topographical analysis of the cortical lesion effects also revealed an uneven striatal response, but, in contrast to that observed for the 6‐OHDA lesion, changes were restricted to dorsolateral areas of the striatum in both brain sides, revealing an apparent complementarity of nigral dopaminergic and cortical influences over striatal NPY neuronal system. Combined unilateral nigral and cortical lesions surprisingly counteracted in a survival time dependent manner the effects of each lesion considered separately. In that condition topographical changes related to the 6‐OHDA lesion totally disappeared and those related to the cortical lesion were attenuated but still present. These results suggest that expression of striatal dopamine—NPY interaction is dependent on corticostriatal transmission. Interestingly lesion of thalamic areas projecting to the striatum did not significantly modify the mean number of NPY‐lr neurons determined per section from the whole striatal surface, but selectively increased the NPY neuron density in the mediodorsal region of the striatum, suggesting that the striatal NPY‐containing neuronal system is also influenced by thalamostriatal projections.