bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Identification and Localization of the Guanine Nucleotide Binding Protein G0 in the Auditory System
Authors: Canlon Barbara , Homburger Vincent , Bockaert Joël 
Published: April 2006

AbstractThe identification of guanine nucleotide binding proteins (G proteins) in guinea‐pig tissues was assessed by the adenosine diphosphate‐ribosylation of the α subunit by Bordetella pertussis toxin using [α32P] nicotinamide adenine dinucleotide as the substrate followed by sodium dodecyl sulphate ‐ polyacrylamide gel electrophoresis and autoradiography. Three tissues (inferior colliculus, neuroblastoma cells, and the organ of Corti) contained G0α (39 kD), as well as Gi2α (40 kD) and Gi1α and/or Gi3α (41 kD). The stria vascularis and the VIIIth nerve contained mainly Gi2α, Gi1α and/or Gi3α, but G0α was barely detectable. A purified preparation of outer hair cells from the organ of Corti contained all three pertussis toxin substrates including G0α, with the Gi2α (40 kD) subunit being the most prominent. The immunocytochemical localization of the G0α subunit was determined by light microscopy after incubating isolated outer hair cells, Hensen cells and the stria vascularis with affinity‐purified anti‐G0α antibodies. In hair cells a positive reaction was observed along the plasma membrane and around the perimeter of the cuticular plate (zona adherens). Positive reaction was also observed within the infracuticular network extending from the cuticular plate towards the nucleus in outer hair cells. Finally, the base of the outer hair cells also contained G0α. However, it is likely that the G0α that is present in this cell region is not within the hair cell itself, but rather in nerve terminals which remained attached during dissection.
Homocysteate, an Excitatory Transmitter Candidate Localized in Glia
Authors: Grandes Pedro , Do Kim Quang , Morino Patrizia , Cuénod Michel , Streit Peter 
Published: April 2006

Abstract l‐Homocysteate, a sulphur‐containing l‐glutamate analogue has recently been proposed as a neurotransmitter candidate. However, the cellular localization of this excitatory amino acid remained to be determined. By means of immunocytochemistry, the localization of homocysteate was accomplished in the cerebellar cortex of rats. Cerebellar glia could be defined as the major store of this compound. Homocysteate, thus, may not be a classical neurotransmitter but rather a member of another class of intercellular messengers that might be termed ‘gliotransmitters’.
Differential Expression of the GABAA Receptor Complex in the Dorsal Thalamus and Reticular Nucleus: An Immunohistochemical Study in the Adult and Developing Rat
Authors: Bentivoglio Marina , Spreafico Roberto , Álvarez‐Bolado Gonzalo , Sánchez Marina P. , Fairén Alfonso 
Published: April 2006

AbstractThe distribution of the GABAA receptor/benzodiazepine receptor/chloride channel complex was investigated in the thalamus of the rat by means of immunohistochemistry in adulthood, as well as during embryonic and postnatal development, using a monoclonal antibody. In adults, the immunoreactivity for the GABAA receptor complex was intensely expressed by neuronal processes throughout the dorsal thalamus. Neuronal perikaryal membranes were frequently outlined by punctate immunostaining; cell bodies, intrathalamic fibre bundles and the internal capsule did not display immunoreactivity for the GABAA receptor. Regional differences in the expression of the receptor were consistently observed: the immunostaining was much lighter in the thalamic reticular nucleus than in the dorsal thalamic nuclei and, among the latter, the anteroventral nucleus and the ventral nuclear complex displayed the most intense immunopositivity. Immunostaining for the GABAA receptor was already expressed in embryos at E14, and was homogeneously distributed throughout the neuropil of the dorsal and ventral thalamic primordia. During the first two postnatal weeks, a regional differentiation of the immunopositivity was appreciable in the thalamus, with a progressive reduction in the reticular nucleus and a parallel increase in the dorsal thalamic structures. Immunoreactive neuronal perikarya were not observed in the thalamus at any developmental stage. The expression of the GABAA receptor complex appeared to have reached a mature configuration by the end of the third postnatal week. These findings indicate that in adults the GABAA receptor is differentially expressed by thalamic nuclear structures, including the reticular nucleus. Furthermore, the maturation of the receptor in the thalamus undergoes a rearrangement during the first postnatal weeks that results in a considerable regression within the reticular nucleus.
Development of Neurons and Glial Cells in Cerebral Cortex, Cultured in the Presence or Absence of Bioelectric Activity: Morphological Observations
Authors: Ramakers G. J. A. , Raadsheer F. C. , Corner M. A. , Ramaekers F. C. S. , van Leeuwen F. W. 
Published: April 2006

AbstractChronic blockade of bioelectric activity (BEA) has been shown to increase neuronal cell death in tissue culture, but the effects of this treatment on non‐neuronal cells have not been investigated. To determine which cell types are affected by chronic suppression of BEA, we investigated their morphological development in primary cultures of rat cerebral cortex, grown with or without the sodium channel blocker tetrodotoxin (TTX). Morphological development was monitored by phase‐contrast microscopy and by immunofluorescent staining of markers specific for neurons (NSE, MAP2, B‐50, and the 200 kD neurofilament protein), astrocytes (GFAP), oligodendrocytes (galactocerebroside), macrophages (ED‐1) and fibroblasts (fibronectin). Neurons in control cultures steadily increased in size and elaborated a dense network of axons and dendrites during the first 3 weeks. Astrocytes proliferated strongly and formed a ‘bottom‐layer’ on which other cells grew. Part of the astrocytes migrated into the peripheral area of the culture, but retracted to the centre after 14 days in vitro (DIV). Oligodendrocytes and macrophages also increased in number, but oligodendrocytes were completely lost by 28 DIV. After 3 weeks, axons that had grown into the periphery of the culture gradually retracted and/or degenerated, following the retracting astrocytes. Some of the neurons died after 21 DIV, but a large part persisted until 42 DIV. Upon TTX treatment from 5/6 DIV, cultures with few macrophages showed an increase in the proportion of necrotic nuclei at 14 and 21 DIV. The retraction of peripherally located fibres was accelerated by 3–4 days and their degeneration was augmented. Neuronal density decreased to zero between 21 and 42 DIV. Astrocytes showed a clear decrease in density from 28 DIV. Conversely, the density of macrophages was increased about two‐fold from 14 DIV. These results indicate that both neurons and glia are affected by chronic TTX treatment.
Absence of Nerve – muscle Interaction Influences the Survival of Developing Motoneurons
Authors: Burls A. , Subramaniam Krishnan , Lowrie M. B. , Vrbová G. 
Published: April 2006

AbstractFollowing sciatic nerve crush at birth, ∼70% of motoneurons to the soleus and 60% of motoneurons to the tibialis anterior (TA) and to the extensor digitorum longus (EDL) die. However, following nerve injury at 5 days, there is negligible motoneuron death. We investigated whether the interaction between the nerve and its target during these 5 days is an important factor for the ability of the motoneuron to survive injury. Nerve‐muscle interaction was blocked shortly after birth by α‐bungarotoxin (BTX) and the effect on motoneuron survival after subsequent injury was examined. It was confirmed that sciatic nerve crush at 5 days produced no significant reduction in motoneuron numbers. However, if nerve crush was preceded by paralysis with α‐bungarotoxin, the number of surviving motoneurons after nerve injury at 5 days was substantially reduced. On the operated side only 43 ± 6.68% of the motoneurons of the soleus pool survived and even fewer, 14 ± 5.0%, in the TA and EDL pool. In a control group of animals paralysed with α‐bungarotoxin at birth but receiving no nerve crush, there was no appreciable reduction in the motoneuron numbers at 28 days in either motor pool. It is concluded that blocking of nerve‐muscle interaction by paralysis in early postnatal life reduces the motoneurons' ability to survive nerve injury later in life, and that this effect is more severe for the motoneurons to the TA and EDL than to the soleus.
Calcium Influx Induced by Stimulation of ATP Receptors on Neurons Cultured from Rat Dorsal Root Ganglia
Authors: Bouvier M. M. , Evans M. L. , Benham C. D. 
Published: April 2006

AbstractA combination of microspectrofluorimetry and single cell voltage‐clamp was used to examine the response to ATP of cultured neurons from rat dorsal root ganglia. ATP activated an inward current and a rise in internal calcium concentration that was dependent on the external calcium concentration and on the magnitude of the ATP‐induced current response. The response was not affected by prerelease of internal calcium stores with caffeine. The rise in internal calcium was increased at hyperpolarized membrane potentials as the calcium driving force was increased. These results demonstrate that the ATP‐gated channels in these cells can admit a significant amount of calcium in a physiological calcium gradient. This alternative calcium entry pathway could provide an internal calcium signal that is spatially distinct to that generated by voltage‐gated calcium entry.
Paradoxical Modulation of Nociception in Mice by Barbiturate Agonism and Antagonism: Is a GABA Site Involved in Nociception?
Authors: Carmody John , Knodler Leigh , Murray Stuart 
Published: April 2006

AbstractIn a battery of four acute and chronic nociceptive tests, the GABA antagonist picrotoxin produces a uniform and sustained analgesia in mice. By contrast, barbiturates which have been presumed to act at the same receptor produce mixed and paradoxical actions. At a standard time of 10 min after drug administration a convulsant barbiturate [5‐ethyl‐5‐(3′‐rnethyI‐but‐2′‐enyl)‐barbituric acid] produced analgesia in three tests but had no effect in the fourth; a pure hypnotic barbiturate (amylobarbitone) produced hyperalgesia in three tests but analgesia in the fourth; while the mixed hypnotic‐convulsant pentobarbitone produced hyperalgesia in two of the tests and was without any effect in the other two. There was no pattern in these results with respect to acute or chronic nociceptive tests. Surprisingly, with extended observation using the tail‐flick test both pentobarbitone and the pure hypnotic (amylobarbitone) gave early hyperalgesia followed by analgesia; the convulsant barbiturate gave only analgesia. The results suggest a role for GABAA receptors in the transmission of nociceptive information; they also suggest that barbiturates act at quite a different receptor.
C‐fos Induction in the Spinal Cord after Peripheral Nerve Lesion
Authors: Williams Simon , Evan Gerard , Hunt Stephen P. 
Published: April 2006

AbstractImmunocytochemical localization of a product of the proto‐oncogene c‐fos, Fos protein, was used to map the activity of a subset of rat spinal neurons at 3 days, 3 weeks and 3 months following section of the sciatic nerve. In a well‐established experimental paradigm, the gene was induced by activation of primary afferent fibres with brief noxious sensory stimulation under anaesthetic. Central sciatic projections were demonstrated with isolectin B4 counterstain and GAP43 immunocytochemistry. In Rexed's lamina II of the spinal cord, in which there is somatotopic organization of afferent terminals, Fos‐positive neurons were largely restricted to the projection area of intact peripheral nerves. Three days after a sciatic nerve lesion, the number of Fos‐positive neurons in a cord region innervated by the saphenous nerve was similar to control levels, but was markedly increased by 3 weeks, remaining elevated at 3 months. Three weeks after sciatic nerve section the lectin stain in the area of sciatic representation had almost completely disappeared, and conversely GAP43 staining had greatly intensified. There was no evidence of invasion by Fos‐immunoreactive cells of the area of sciatic representation. After 3 months both the size and the intensity of the lectin gap, and of the corresponding area of increased GAP43 immunoreactivity, appeared reduced. Thus a peripheral nerve lesion was followed by a delayed increase in excitability of the spinal cord as assessed by c‐fos expression, so that greater numbers of second‐order neurons were activated by sensory stimulation of an adjacent intact nerve. These changes may be related to the sensory abnormalities which follow nerve damage.
Enkephalin Expression in Spinal Cord Neurons is Modulated by Drugs Related to Classical and Peptidergic Transmitters
Authors: Foster G. A. , Eiden L. E. , Brenneman D. E. 
Published: April 2006

AbstractThe effects of various neurotransmitter agonists and antagonists on the synthesis and release of methionine enkephalin (mENK) in neuronal cultures of mouse spinal cord and dorsal root ganglia have been measured. Blockade of electrical activity with tetrodotoxin between days 9 and 13 in culture caused a > 95% decrease in the number of mENK‐immunoreactive neurons. This effect was also seen upon the blockade of glycine and β‐adrenergic receptors with strychnine and propranolol, respectively, and stimulation of GABA receptors with muscimol. Stimulation of β‐adrenergic receptors with isoproterenol, or blockade of glutamate and GABA receptors with 2‐aminophosphonovalerate and strychnine, respectively, had a qualitatively opposite action on both the number of mENK‐immunoreactive neurons and enkephalin peptide levels measured by radioimmunoassay. Application of substance P also enhanced the mENK cell number. These data suggest that, at least in the spinal cord, characteristics other than the average level of impulse activity in the afferent input may be critical to the regulation of expression of mENK.
Chronic Epileptic Foci in Neocortex: In Vivo and In Vitro Effects of Tetanus Toxin
Authors: Brener Karin , Amitai Yael , Jefferys John G.R. , Gutnick Michael J. 
Published: April 2006

AbstractInjection of 0.2–3.0 ng of tetanus toxin into rat parietal neocortex resulted in permanent (> 7 months) changes in the local circuit properties of this tissue. It caused excessive synchronization of neuronal activity. This was seen as spontaneous paroxysmal field potentials and/or evoked all‐or‐none population burst discharges. Such activity was recorded widely over the parietal and temporal areas of both the injected and the contralateral hemispheres from as little as 16 h after injection up to the maximum survival time of 7 months. Several observations suggest that the speed with which the hypersynchronous activity spread to the opposite hemisphere reflects transport of the toxin through corticocortical axons, and consequent blockade of synaptic inhibition. However, from what is known of the half life of the peptide in brain, it is unlikely that the persistent, widespread distribution of epileptiform discharge several months after injection was due to the continued presence of toxin. Thus, intracortical application of tetanus toxin provides a good experimental model of chronic focal epilepsies, and raises fundamental questions regarding the long term regulation of local circuit properties in the neocortex.
Specific Reinnervation of Lesioned Mouse Striatum by Grafted Mesencephalic Dopaminergic Neurons
Authors: Zuddas Alessandro , Corsini Giovanni U. , Barker Jeffery L. , Kopin Irwin J. , di Porzio Umberto 
Published: April 2006

AbstractSelective lesions of the dopaminergic nigrostriatal system and embryonic neuron grafts were used to study the mechanism by which exogenous neurons can restore transmitter function and to examine CNS development and plasticity. C57BL mice treated with acetaldehyde/1‐methyl‐4‐phenyl‐1,2,3,6‐tetra‐hydropyridine show irreversible loss of substantia nigra dopaminergic neurons. Implants of embryonic mesencephalic dopaminergic neurons functionally reinnervate the striatum and form a dense network of fibres; ∼20% of the implanted dopaminergic cells survive for several months. However, dopaminergic fibre outgrowth and mesencephalic graft development appear lower in control, non‐lesioned, animals. Moreover, implants of embryonic hypothalamic dopaminergic neurons show little or no survival. These results indicate that interactions between embryonic and adult neurons are selective. We suggest that this specificity may be sustained by the action of still unknown trophic and/or tropic factors, possibly produced by the lesioned striatum and by putative inhibitory mechanisms of cell migration and neuritic outgrowth.
Functional Connections Formed by Saphenous Nerve Terminal Sprouts in the Dorsal Horn Following Neonatal Sciatic Nerve Section
Authors: Shortland Peter , Fitzgerald Maria 
Published: April 2006

AbstractThe rostrocaudal distribution of saphenous nerve inputs into the lumbar dorsal horn from L2 to L6 has been investigated in urethane anaesthetized rats whose left sciatic nerve was cut and ligated at birth. In normal cord, electrical stimulation of the saphenous nerve evoked dorsal horn spikes in L2 to caudal L4. Few or no spikes were evoked in L5. After neonatal sciatic nerve section, saphenous nerve stimulation evoked spikes throughout segments L2 to L6. Dorsal horn cell receptive fields were also altered following neonatal sciatic nerve section. A somatotopic map of the lumbar enlargement in normal rats was constructed from the receptive fields (RFs) of adjacent dorsal horn cells. Cells with RFs in the saphenous skin region were concentrated in L3 and rostral L4 and very few were found in L5. After neonatal sciatic nerve section, however, a substantial number of cells with low threshold saphenous skin RFs were also found in caudal L4 and throughout L5. These results show that the central saphenous nerve terminal sprouts that grow into the sciatic terminal region following neonatal sciatic nerve section (Fitzgerald, 1985, J. Comp. Neurol., 240, 414–422; Fitzgerald et al., 1990, J. Comp. Neurol., 300, 370–385) form functional connections. This results in dorsal horn cells that are not normally influenced by saphenous nerve inputs developing substantial low threshold RFs in saphenous nerve skin regions.
Interaction of Noradrenergic and Cholinergic Agonists with Ligands Increasing K‐conductance of Guinea Pig Hippocampal Neurons, in vitro
Authors: Bijak M. , Misgeld U. , Müer W. 
Published: April 2006

AbstractSingle electrode current clamp and voltage clamp recordings were employed to study the effects of noradrenergic agonists and a cholinergic agonist (carbachol, Cch) on the resting membrane potential of CA3 neurons in guinea pig hippocampal slices. Stimulation of muscarinic and β‐adrenergic receptors depolarized, and stimulation of α1‐adrenergic receptor hyperpolarized, CA3 neurons but the membrane potential changes were small. Hyperpolarizations or outward currents induced by baclofen, adenosine or serotonin (5‐HT) were strongly potentiated by α‐noradrenergic agonists and suppressed by Cch at concentrations ten times lower than those having any direct effects on membrane potential. Both the enhancement of the baclofen‐induced hyperpolarization by phenylephrine and its suppression by Cch were pronounced at low concentrations of baclofen, but diminished at higher concentrations. The modulatory effects persisted after blockade of sodium spikes by tetrodotoxin and after blockade of fast inhibitory and excitatory synaptic transmission by picrotoxin and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione. Our data suggest that, through the postsynaptic interaction with ligands activating potassium conductance, noradrenergic and muscarinic receptor stimulation can exert a stronger inhibitory and excitatory effect on CA3 pyramidal neurons at their resting membrane potential than would be expected from the changes in membrane potential induced by these neuromodulators on their own.
The Projections of Mitral Cells from Small Local Regions of the Olfactory Bulb: An Anterograde Tracing Study Using PHA‐L (Phaseolus vulgaris Leucoagglutinin)
Authors: Buonviso N. , Revial M. F. , Jourdan F. 
Published: April 2006

AbstractNumerous anatomical and electrophysiological studies have demonstrated a lack of simple point‐to‐point topographical relationships between the olfactory bulb and primary olfactory projection areas. They reveal instead, a complex pattern of divergence and convergence. Furthermore, several authors reported that a single mitral cell could project onto different widely spaced cortical regions of the olfactory cortex. In the present study, we attempted to label the projections of a few mitral cells so close together so that they might be assumed to be connected to the same glomerulus, and to determine if these cells had similar patterns of axonal projections. For this purpose small Phaseolus vulgaris leucoagglutinin (PHA‐L) injections were performed in the olfactory bulb of adult rats. We found that labelling two to five mitral cells, lying close together in the mitral cell layer, resulted in well‐delineated patches of labelled fibres in the cortex. The number of patches was not related to the number of labelled mitral cells but the fibre density in each patch increased with the number of PHA‐L filled somata in the olfactory bulb. We conclude that mitral cells lying close together in the mitral cell layer have similar patterns of axonal projections. Functional implications of such an organization in olfactory coding is discussed.
Characterization of a Voltage‐dependent Calcium Current in the Human Neuroblastoma Cell Line SH‐SY5Y During Differentiation
Authors: Toselli M. , Masetto S. , Rossi P. , Taglietti V. 
Published: April 2006

AbstractIn the presence of retinoic acid, cultured human neuroblastoma SH‐SY5Y cells grow processes indicative of neuronal differentiation. A voltage‐gated Ca current is already present in undifferentiated cells. A gradual increase of the Ca current density occurs during cell differentiation. According to kinetic and pharmacological properties, Ca currents in differentiated cells are indistinguishable from those elicitable in undifferentiated cells and resemble features of the high‐voltage activated currents present in mammalian neuronal cells. ω‐conotoxin strongly depresses high‐voltage activated currents, both in undifferentiated and in differentiated SH‐SY5Y cells. Interestingly, the Ca agonist Bay K 8644 is effective, albeit with great variability from cell to cell, only in differentiated cells and only when barium is the current carrier through the Ca channels. A diversity of high‐voltage activated Ca channels of distinct pharmacology has been recently observed in other kinds of neurons. This requires a redefinition of the role that voltage‐dependent Ca channel subtypes can play in mammalian neurons.