bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Study of Passive Membrane Properties and Morphology Reveals Neuronal Differences Along the Sagittal Axis of the Ventral Periaqueductal Grey Matter
Authors: Sánchez D. , Armengol J. A. , Ribas J. 
Published: April 2006

AbstractThe membrane properties of the neurons located in the ventral part of the periaqueductal grey (PAG) of the guinea‐pig were studied using an in vitro slice preparation. Cells had low values of resting membrane potential (−53.3 ± 1.3 mV, mean ± standard error), high input resistance (195.5 ± 16.2 MΩ) and moderate values of membrane time constant (12.6 ± 0.7 ms). The last two parameters changed as recordings were made along the sagittal axis, higher values corresponding to the more rostral cells. Three main neuronal types—fusiform, triangular and stellate—were found in the ventral PAG using intracellular injection of Lucifer yellow. A study of the cell number and cell density was carried out in coronal and sagittal sections of the ventral PAG. This analysis showed a clear gradient of size in this region arising from the gradual disappearance of large (17 to 40 μm) neurons in the caudorostral direction. The neuronal density also increased in this direction. Therefore, some electrotonic and morphological parameters differ along the sagittal axis. These findings suggest a larger neuronal heterogeneity of the caudal part of the PAG, and might contribute to a functional segregation of this region.
Direct Immunohistochemical Evidence of the Existence of 5‐HT1A Autoreceptors on Serotoninergic Neurons in the Midbrain Raphe Nuclei
Authors: Sotelo Constantino , Cholley Béatrice , El Mestikawy Salah , Gozlan Henri , Hamon Michel 
Published: April 2006

AbstractPhysiological, pharmacological and radioautographic binding studies have suggested the presence of the 5‐HT1A autoreceptors on midbrain serotoninergic neurons. The recent production of specific anti‐rat 5‐HT1A receptor antibodies in rabbits injected with a synthetic peptide has provided a tool to examine this problem directly. Using the immunoperoxidase method to localize the receptor protein, neurons of all the sizes and forms characterizing the neuronal populations in the dorsal and median raphe nuclei were stained. Reaction product was distributed along the neuronal surface, outlining the contours of perikarya and dendrites in a continuous but uneven manner. Intracellular staining was scarce and confined to the perinuclear region. Double immunohistochemical staining using the anti‐5‐HT1A receptor antibodies and an anti‐serotonin (5‐HT) antiserum showed that all the 5‐HT1A receptor immunoreactive neurons in the dorsal raphe, and the vast majority of them in the median raphe, are serotoninergic neurons. These data provide the first direct demonstration of the existence of 5‐HT1A autoreceptors on the perikarya and dendrites of serotoninergic neurons in the anterior raphe nuclei.
Active and Passive Membrane Properties of Spinal Cord Neurons that Are Rhythmically Active during Swimming in Xenopus Embryos
Authors: Soffe S. R. 
Published: April 2006

AbstractCellular properties have been examined in ventrally located Xenopus spinal cord neurons that are rhythmically active during fictive swimming and presumed to be motoneurons. Resting potentials and input resistances of such neurons are ‐75 ± 2 mV (mean ± standard error) and 118 ± 17 MΩ respectively. Most cells fire a single impulse, 0.5 to 2.0 ms in duration and 48.5 ± 1.8 mV in amplitude, in response to a depolarizing current step. A minority fire several spikes of diminishing amplitude to more strongly depolarizing current. Cells held above spike, threshold fire on rebound from brief hyperpolarizing pulses. Spikes are blocked by 0.1 to 1.0 μM tetrodotoxin (TTX) and are therefore Na+‐dependent. Current/voltage (I/V) plots to injected current are approximately linear near the resting potential but become non‐linear at more depolarized levels. Cells recorded in TTX with CsCl‐filled microelectrodes show a linearized I/V plot at depolarized membrane potentials suggesting the normal presence of a voltage‐dependent K+ conductance activated at relatively depolarized levels. Most cells recorded in this way but without TTX fire long trains of spikes of near constant amplitude, pointing to a role of the K+ conductance in limiting firing in normal cells. Spike blockage with TTX reveals, in some cells, a transient depolarizing Cd2+‐sensitive and therefore presumably Ca2+‐dependent potential that increases in amplitude with depolarization. Cells in TTX, Cd2+, and strychnine, and recorded with CsCl‐filled microelectrodes to block active conductances respond to hyperpolarizing current steps with a two component exponential response. The cell time constant (τ0) obtained from the longer of these by exponential peeling is relatively long (mean 15.7 ms). These findings contribute to an increased understanding of the cellular properties involved in spinal rhythm generation in this simple vertebrate.
The Course of Fibre Diameter Classes Through the Chiasmatic Region in the Ferret
Authors: Reese B. E. , Baker G. E. 
Published: April 2006

AbstractThe present study has examined the transition of fibre order from the optic nerve through the optic chiasm and into the optic tract in the ferret's retinofugal pathway. Semi‐thin sections through the chiasmatic region were examined in normal and in monocularly enucleated ferrets in order to display the segregation of the different axon diameter classes as the fibres pass from the optic nerve into the optic tract, and to determine, for each diameter class, where the crossed and uncrossed components become separated in the chiasmatic region.As demonstrated in the preceding manuscript, fine and coarse optic axons begin to segregate from the medium optic axons rostral to the fusion of the two optic nerves. This segregation continues in the chiasmatic region where the different axon diameter classes decussate at different rostro‐caudal levels: the fine and coarse diameter axons decussate rostrally, accumulating along the ventral, superficial surface of the contralateral half‐chiasm, while the medium diameter axons continue caudally before crossing the midline. These two populations, a ventral, crossed (fine and coarse) population and a dorsal, yet‐to‐cross (medium) population are discriminable not only by their size in the chiasmatic region, but also by a thin invagination of hypothalamic neuropil separating them at their lateral extreme. The population of ipsilaterally projecting fibres is composed of both fine and medium optic axons. No coarse optic axons project ipsilaterally in the ferret: these fibres all decussate rostrally in the optic chiasm, intermingled with many of the decussating fine fibres.The fibre ordering in the adult ferret's optic chiasm is interpreted as reflecting a gradient of axonal arrival during development, with successively later arriving optic axons entering one of the two optic tracts at a progressively more superficial, rostral and ventral, location in the chiasmatic region. A fibre's position and time of arrival may influence its subsequent crossed or uncrossed course during the period of axonal ingrowth in development.
Sites of [3H]taurine Uptake in the Rat Substantia Nigra in Relation to the Release of Taurine from the Striatonigral Pathway
Authors: Corte L. Delia , Bolam J. P. , Clarke D. J. , Parry D. M. , Smith A. D. 
Published: April 2006

AbstractThe autoradiographic localization of radiolabelled taurine taken up in the rat substantia nigra in vivo together with conditions of release of the [3H]taurine taken up into brain slices were studied to determine whether they are consistent with the hypothesis that taurine may act as a neurotransmitter in the striatonigral pathway.At the light microscopic level the main cellular elements that became radiolabelled following the injection of [3H]taurine into the substantia nigra could be identified as glial cells. Electron microscope autoradiography confirmed that a subpopulation of glial cells including astrocytes, pericytes, and oligodendrocytes were radiolabelled and that neuronal perikarya were not radiolabelled. In addition, axonal elements including both terminal and preterminal boutons were found to have silver grains overlying them and were thus considered to be radiolabelled. This was supported by a quantitative analysis of the distribution of the silver grains; whereas glial elements had a significantly higher number of grains associated with them than with any other structure, axonal elements had a significantly greater number of grains than dendritic structures.Release of the preloaded [3H]taurine from superfused slices of substantia nigra occurred in response to veratridine, was calcium‐dependent and was sensitive to inhibition by high magnesium concentrations or tetrodotoxin. Following the destruction of neurons in the striatum by ibotenic acid injections, although the weight of the ipsilateral substantia nigra was reduced, the uptake of [3H]taurine was not altered. In contrast to this, the veratridine‐stimulated release was markedly attenuated, implying that the destruction of striatal neurons causes the loss of sites in the substantia nigra from which exogenous taurine is released.These results add further support to previous suggestions that taurine might act as a neurotransmitter or neuromodulator in the striatonigral pathway.
Effects of Putative Neurotransmitters of the Carotid Body on its Own Glomus Cells
Authors: Eyzaguirre C. , Monti‐Bloch L. , Woodbury J. W. 
Published: April 2006

AbstractCarotid body glomus cells produce and release acetylcholine (ACh), catecholamines, and neuropeptides, and there is biochemical evidence that these cells possess receptors for these substances. Thus, we studied the effects of cholinergics [ACh, nicotine (Nic), bethanechol (BN)] and peptides [met‐enkephalin (ME), substance P (SP)] on the membrane potential (Em), voltage noise (Erms), and input resistance (R0) of glomus cells. Sliced carotid bodies (for cell visualization) of cats, rabbits, and mice were used.The mean Em and R0 of rabbit glomus cells were lower than those of cat and mouse. R0 of mouse cells was the largest, whereas Erms was similar in all species. The various agents had qualitatively similar effects on the cells of the three species although some quantitative differences were sometimes observed. But, for simplicity, results were pooled.ACh depolarized most cells (effect depressed by zero [Ca2+]0 and Mn2+), reduced their resistance, and induced variable changes in Erms. Different ACh doses produced non‐linear effects on ΔEm. Nic and BN also depolarized most cells, reducing R0 and Erms. Atropine depressed the cell responses to BN; α‐bungarotoxin the depolarizing response to Nic. ME and SP depolarized most cells, but only ME significantly reduced R0. Neither peptide significantly changed voltage noise.Comparing the effects of all drugs showed that BN was the most effective depolarizing agent, producing the largest reductions in R0. There were negative correlations between ΔEm and ΔR0 with the cholinergics and SP; correlations between ΔErms and ΔR0 were significant and positive only with the cholinergics.These results confirm the presence of nicotinic, muscarinic, and peptidergic receptors in glomus cells. The similar effects of cholinergics and peptides and those of flow interruption and anoxia suggest that the latter may partly act via autoreceptors for the released transmitters.
Long‐Term Reduction in the Number of C‐Fibre Nociceptors Following Capsaicin Treatment of a Cutaneous Nerve in Adult Rats
Authors: Pini Adrian , Baranowski Richard , Lynn Bruce 
Published: April 2006

AbstractThe structure and function of C‐ and A‐fibres have been studied 3–12 months following a single 30 min exposure of the saphenous nerve of adult rats to 1% capsaicin. Examination of nerve cross‐sections showed that the number of C‐fibres was reduced by 36%, but A‐fibres were unaffected. The remaining C‐fibres included many that were unusually small in size. The changes were not restricted to the treatment site but were found over at least a further 10 mm proximal and distal to it. In treated nerves, the C‐fibre component of the compound action potential was reduced in size relative to the Aαβ component. Single unit studies revealed that an unusually high proportion of C‐fibres had no cutaneous receptive field (54%, compared with 28% in controls). There was no such change for A‐fibres. The conduction velocity range for C‐fibre units in treated nerves was almost normal, but this sample contained an unusually low proportion of polymodal nociceptors. Allowing for the fall in total numbers and the reduction in units with cutaneous receptive fields, it was calculated that overall the numbers of C‐polymodal nociceptor units had fallen by 74%. No significant changes in number had occurred in the other classes of C‐afferents. The reduction in the numbers of nociceptive C‐fibres is likely to be the direct cause of the reduction in pain responses and in neurogenic inflammation that several groups have reported following treatment of adult rats with capsaicin. Reduction in the numbers of C‐fibre is also likely to be the reason for reduced neuropeptide levels seen in tissues innervated by treated nerves.
Neuropeptide Levels after Pentylenetetrazol Kindling in the Rat
Authors: Marksteiner Josef , Lassmann Hans , Saria Alois , Humpel Christian , Meyer Dieter K. , Sperk Günther 
Published: April 2006

AbstractLevels of several neuropeptides were measured in the frontal cortex, dorsal hippocampus, striatum, and amygdala/pyriform cortex in rats kindled for 5 weeks by daily injection of pentylenetetrazol (30 mg/kg, i.p.). Significantly increased concentrations (by 30–140%) were found in all examined brain areas for neuropeptide Y, somatostatin (except hippocampus) and neurokinin‐like immunoreactivity 10 days after the last kindling session. Similar but less pronounced changes were also found 24 h after the last seizure. The increase in total neurokinin‐like immunoreactivity was due to a marked increase in neurokinin B as revealed by HPLC analysis. Increases in peptide levels, however, were restricted to fully kindled animals. At the same time no changes in levels of substance P, vasoactive intestinal polypeptide and calcitonin gene‐regulated peptide were observed. Cholecystokinin octapeptide was enhanced only in the hippocampus (by 46%). The increases in neuropeptide Y, somatostatin, and neurokinin‐like immunoreactivity subsided after 3 months. A markedly decreased seizure threshold was observed 10 days and 2 months after the final kindling session.No nerve cell degeneration was observed in kindled rats 24 h or 10 days after the last pentylenetetrazol injection. Some animals (2 of 4), however, exhibited signs of blood‐brain barrier damage when examined 24 h after the last kindling session which may reflect the preceding convulsions. No such changes were detected after 10 days.The increases in peptide levels may suggest increased activity of respective neurons which, at least to some degree, may be associated with γ‐aminobutyric acid. The changes in peptide levels may be more closely related to the kindling procedure itself than to the decreased seizure threshold of the animals.
Activation of Calcium Channel Currents in Rat Sensory Neurons by Large Depolarizations: Effect of Guanine Nucleotides and (‐)‐Baclofen
Authors: Dolphin Annette C. , Scott Roderick H. 
Published: April 2006

AbstractCalcium channel currents have been recorded from cultured rat sensory neurons at clamp potentials of between ‐30 and +120 mV. At large depolarizing potentials between +50 and +120 mV, the current was outward. This outward current was shown to be largely due to ions passing through calcium channels, because it was substantially although generally incompletely blocked by Cd2+ (1 mM) and ω‐conotoxin (1 μM). Internal GTP‐γ‐S (100 μM) and to a lesser extent GTP (1 mM) reduced the amplitude and slowed the activation of the outward, as well as the inward calcium channel current. Baclofen (100 μM) reversibly inhibited both the inward and outward currents. These results suggest that the effect of baclofen and G protein activation on calcium channel currents is not due to a shift in the voltage‐dependence of channel availability.
Differential Effects of Glucocorticoids on Corticotrophin‐Releasing Factor in the Rat Pituitary Neurointermediate Lobe and Median Eminence
Authors: Jessop David S. , Chowdrey Hardial S. , Lightman Stafford L. 
Published: April 2006

AbstractWe have investigated the effects of glucocorticoid manipulation on corticotrophin‐releasing factor (CRF‐41) in the neurointermediate lobe (NIL) and median eminence (ME) of the rat using a radioimmunoassay specific for CRF‐41. CRF‐41 content in the NIL (88 ± 7 fmol, mean ± SEM) was not significantly altered by administration of dexamethasone in drinking water for 12 days (67 ± 9 fmol) or adrenalectomy for 12 days (96 ± 17 fmol). The saline‐stimulated increase in NIL CRF‐41 content (154 ± 24 fmol) was not affected by dexamethasone (152 ± 24 fmol) or adrenalectomy (179 ± 21 fmol). In contrast, the content of CRF‐41 in the ME declined following dexamethasone treatment (1247 ± 92 fmol to 864 ± 26 fmol), or adrenalectomy (854 ± 78 fmol). Our results provide further evidence that CRF‐41 in the NIL and ME can be differentially regulated.
Tracing of Neuronal Connections in the Human Brain by Magnetic Resonance Imaging in vivo
Authors: Danek A. , Bauer M. , Fries W. 
Published: April 2006

AbstractAxon degeneration after disruption of fibre tracts in the mammalian nervous system is accompanied by myelin breakdown which leads to changes in its magnetic resonance properties. In two patients with pure motor strokes due to small ischaemic lesions restricted to the internal capsule, magnetic resonance imaging disclosed a narrow band of pathological signal increase descending band‐like into the brain stem and ascending to the precentral gyrus, which corresponded to the well‐known path of the pyramidal tract. The findings suggest that in man anterograde and possibly retrograde fibre degeneration can be traced in vivo by conventional magnetic resonance imaging techniques. Critical conditions are the presence of small, strategically located lesions, appropriate choice of imaging plane, and the interval between time of lesion and of imaging. This demonstration may open a new era for functional neuroanatomy of man.
Serotonin Induces a Cyclic AMP‐Mediated Outwardly Rectifying Slow K+ Current in a Single Identified Snail Neuron
Authors: Paupardin‐Tritsch Danièle , Gerschenfeld H. M. 
Published: April 2006

AbstractIn the F2 neuron of the parietal ganglion of the snail Helix aspersa either bath or iontophoretic application of serotonin (5‐HT) induces an outward current. This current has a long latency (10–60 s) and a slow time course, a 500 ms iontophoretic application of 5‐HT evoking a response lasting 3–5 min. This slow outward current reverses at ‐80 mV, a value equal to EK. After doubling the extracellular K+ concentration the reversal potential of the 5‐HT response is shifted by 19 mV, as predicted by the Nernst equation. The I‐V curves reveal that the 5‐HT‐induced slow outward current is outwardly rectifying. This 5‐HT response is blocked by intracellular Cs+ and tetraethylammonium (TEA+) and by extracellular TEA+ and Ba2+, but is not affected by the removal of extracellular Ca2+ or the intracellular injection of ethyleneglycol‐bis‐(β‐amino‐ethylether)‐N,N,N′,N′‐tetra‐acetic acid (EGTA). These results indicate that the outwardly rectifying slow outward current induced by 5‐HT in the F2 neuron is carried by K+ and is Ca2+‐independent. In the single isolated F2 neuron, 5‐HT induces a 2.5‐fold stimulation of the adenylate cyclase activity. In addition, both the intracellular injection of 3′,5′‐adenosine monophosphate (cAMP) and the application of forskolin mimic the effect of 5‐HT on the F2 neuron. The phosphodiesterase inhibitor isobutylmethylxanthine also induces a slow outward current and potentiates the 5‐HT response. The intracellular injection of a synthetic 20‐residue peptide inhibitor of the cAMP‐dependent protein kinase blocks the slow outward K+ current induced by 5‐HT. These results show that in the F2 neuron, 5‐HT elicits a slow K+ current via the stimulation of adenylate cyclase, an increase in intracellular cAMP and the activation of the cAMP‐dependent kinase which probably phosphorylates a population of outwardly rectifying K+ channels or some protein/s associated with these channels.
Cloning and Characterization of the Rat Gene Encoding GAP‐43
Authors: Grabczyk Ed , Zuber Mauricio X. , Federoff Howard J. , Ng Shi‐Chung , Pack Alison , Fishman Mark C. 
Published: April 2006

AbstractGAP‐43 is a gene expressed only in the nervous system. The protein product is believed to be important to neuronal growth and plasticity. Most, and likely all, neurons express high levels of GAP‐43 during periods of neurite elongation. To initiate studies of GAP‐43 gene regulation we have cloned the rat gene encoding GAP‐43. The GAP‐43 gene includes three exons. The first exon encodes only the amino terminal 10 amino acids, which corresponds to the membrane targeting domain of GAP‐43. The second exon encodes a putative calmodulin binding domain and a protein kinase C phosphorylation site. The 5′‐flanking sequence is unusual in that it lacks CAAT or TATA elements, and directs RNA transcription initiation from several sites. Some of the transcription start sites are used to a different degree in the central and peripheral nervous systems.
Responses of Regenerating Rat Retinal Ganglion Cell Axons to Contacts with Central Nervous Myelin in vitro
Authors: Vanselow J. , Schwab M. E. , Thanos S. 
Published: April 2006

AbstractIn order to investigate the responses of neurites to myelin in vitro, retinal explants obtained from adult rats were cultured on poly‐L‐lysine and laminin. Regenerating adult ganglion cell axons were confronted with rat central myelin which was adsorbed on culture dishes. When the explants were placed directly on the myelin, axons did not grow out. Alternatively, when the explants were placed at a certain distance from the myelin, massive outgrowth of axons was observed. When axonal growth cones encountered the myelin, they displayed various reactions. All single axons observed immediately stopped growing after encountering the myelin border. All of them remained for at least 4 h at the border. Sixteen per cent of them remained in this ‘resting state’ throughout the time of observation (2–5 days). Nineteen per cent of the axons degenerated following contact with the myelin. The majority of axons were able to circumvent the myelin either by backbranching (21%) or by growing in another direction with the leading growth cone (37%). Eight per cent of the axons were observed to enter the myelin. The results indicate that central myelin represents a non‐permissive obstacle for growing adult axons. This observation is in conformity with the inability to regenerate that is typical of lesioned optic nerve axons in situ.
Effects of Corticotrophin Releasing Factor, Muscarine and Somatostatin on Rubidium and Potassium Efflux from Mouse AtT‐20 Pituitary Cells
Authors: Luini A. , Brown D. A. 
Published: April 2006

AbstractEffects of secretagogues and anti‐secretagogues of ACTH secretion on K+ permeability in the clonal pituitary cell line AtT‐20 were measured by recording 86Rb or 42K efflux. Efflux was accelerated by the secretagogues K+, corticotrophin, forskolin, isoprenaline, and the Ca‐ionophore A23187. Efflux was reduced by the inhibitors somatostatin, muscarine, and oxotremorine, or by removing external Ca. Efflux was also reduced by the K+‐channel blocking compound d‐tubocurarine but not by tetraethylammonium. Muscarine, oxotremorine, somatostatin, and 0 Ca2+ also reduced intracellular Ca2+ measured by quin‐2 fluorescence. It is suggested that most of the resting 86Rb or 42K efflux measured under these conditions occurs via tubocurarine‐sensitive Ca2+‐dependent K+‐channels, and that changes in efflux rate produced by secretagogues or anti‐secretagogues are secondary to changes in intracellular Ca2+.