bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peripheral and Central Mechanisms of NGF‐induced Hyperalgesia
Authors: Lewin Gary R. , Rueff Alain , Mendell Lorne M. 
Published: April 2006

AbstractMechanisms underlying the hyperalgesia induced by a single systemic injection of nerve growth factor (NGF) in adult rats were studied in vivo. A single dose of NGF initiated a prolonged thermal hyperalgesia to a radiant heat source within minutes that lasted for days. Animals which had been pretreated with the mast cell degranulating compound 48/80 or either one of two specific 5‐hydroxytryptamine receptor antagonists (ICS 205–930 and methiothepin) also developed an NGF‐induced thermal hyperalgesia, but onset was delayed by more than 3 h. In the presence of ICS 205‐930 or methiothepin the early component NGF‐induced hyperalgesia was reversed and the animals responded with an initial hypoalgesia to the thermal stimuli. Whereas these results indicate a peripheral mechanism for the initial thermal hyperalgesia, the later phase (7 h–4 days after NGF) appeared to be centrally maintained, since it could be selectively blocked by the non‐competitive NMDA receptor antagonist MK‐801. In contrast to the almost immediate thermal hyperalgesia following a single injection of NGF, a significant mechanical hyperalgesia began only after a 7 h latency. This NGF‐induced mechanical hyperalgesia was not blocked by any of the treatments that attenuated the thermal hyperalgesia, indicating that a separate mechanism may be involved. Additional electrophysiological experiments showed that NGF‐induced hyperalgesia was not maintained by an increased amount of spontaneous activity in C‐fibres. A final result showed that endogenous release of NGF in a model of acute inflammation (complete Freund's adjuvant‐induced inflammation) may be involved in the development of thermal hyperalgesia, since it could be blocked by concomitant treatment with anti‐NGF antisera. These data indicate that NGF‐induced thermal and mechanical hyperalgesia are mediated by different mechanisms. The rapid onset component of thermal hyperalgesia is due to a peripheral mechanism involving the degranulation of mast cells, whereas the late component involves central NMDA receptors. In contrast, the NGF‐induced mechanical hyperalgesia seems to be independent of mast cell degranulation or central NMDA receptor sites.
REVIEW
Authors: Obeso J. A. , Grandas F. , Herrero M. T. , Horowski R. 
Published: April 2006

AbstractMore effective measures to control and replace the dopaminergic deficit of Parkinson's disease are being actively sought. One basic problem is how the striatal dopamine loss should be replaced in order to mimic most accurately the physiological state. Animal electrophysiology indicates that the dopaminergic nigrostriatal pathway has a dual tonic and phasic action. Intermittent dopaminergic stimulation is associated with behavioural hyposensitivity both in animal models and in patients with Parkinson's disease. Continuous dopaminergic stimulation provides a tonic background and improves some clinical problems but is also associated with tolerance. None of the available pharmacological approaches can restore the dopamine deficiency of Parkinson's disease to physiological levels. Continuous dopaminergic stimulation for <24 h, associated with small doses of levodopa or a short‐acting dopamine agonist, appears to be the best, albeit imperfect, therapeutic approach until other, more efficacious remedies are developed.
Computational Structure of Visual Callosal Axons
Authors: Innocenti Giorgio M. , Lehmann Patricia , Houzel Jean‐Christophe 
Published: April 2006

AbstractWe analysed the activation profiles obtained by simulating invasion of an orthodromic action potential in eleven anterogradely filled and serially reconstructed terminal arbors of callosal axons originating and terminating in areas 17 and 18 of the adult cat. This was done in order to understand how geometry relates to computational properties of axons. In the simulation, conduction from the callosal midline to the first bouton caused activation latencies of 0.9‐3.2 ms, compatible with published electrophysiological values. Activation latencies of the total set of terminal boutons varied across arbors between 0.3 and 2.7 ms. Arbors distributed boutons in tangentially segregated terminal columns spanning one or, more often, several layers. Individual columns of one axon were frequently activated synchronously or else within a few hundred microseconds of each other. Synchronous activation of spatially separate columns is achieved by: (i) long primary or secondary branches of similar calibre running nearly parallel to each other for several millimetres; (ii) variations in the calibre of branches serially fed to separate columns by the same primary or secondary branch; (iii) exchange of high‐order or preterminal branches across columns. The long, parallel branches blatantly violate principles of axonal economy. Simulated alterations of the axonal arbors indicate that similar spatiotemporal patterns of activity could, in principle, be obtained by less axon‐costly architectures. The structure of axonal arbors, therefore, may not be determined solely by the type of spatiotemporal activation profiles it achieves in the cortex but also by other constraints, in particular those imposed by developmental mechanisms.
Differential Expression of Two Glial Glutamate Transporters in the Rat Brain: an In Situ Hybridization Study
Authors: Torp R. , Danbolt N. C. , Babaie E. , BjØrås M. , Seeberg E. , Storm‐Mathisen J. , Ottersen O. P. 
Published: April 2006

AbstractThe distributions of the mRNAs encoding the l‐glutamate transporters GLT1 and GLAST were examined in the rat brain by in situ hybridization using 35S‐labelled oligonucleotide probes. Probes directed to GLT1 produced dense labelling in the hippocampus, neocortex and neostriatum, and weak labelling in the cerebellum. In contrast, GLAST mRNA appeared to be greatly enriched in the cerebellum compared to other brain regions. While the intensity of the labelling for GLAST and GLT1 varied among different regions, their cellular distributions appeared to coincide inasmuch as both mRNAs were mainly expressed by glial cells. Labelling occurred, inter alia, in glial cells throughout the hippocampus, and in Golgi epithelial cells in the Purkinje cell layer of the cerebellum.
Calcium Channel Currents in Undifferentiated Human Neuroblastoma (SH‐SY5Y) Cells: Actions and Possible Interactions of Dihydropyridines and ω‐Conotoxin
Authors: Reeve Helen L. , Vaughan Peter F. T. , Peers Chris 
Published: April 2006

AbstractCa2+ channel currents were recorded in undifferentiated human neuroblastoma (SH‐SY5Y) cells with the whole‐cell patch‐clamp technique, using 10 mM Ba2+ as charge carrier. Currents were only evoked by depolarizations to ‐30 mV or more positive (holding potential ‐80 mV), inactivated partially during 200 ms depolarizing steps, and were abolished by 150 μMCd2+. Currents could be enhanced by Bay K‐8644 and partially inhibited by nifedipine, suggesting that they arose in part due to activation of L‐type Ca2+ channels. Currents were also inhibited by the marine snail peptide ω‐conotoxin GVIA (ω‐CgTx). At a concentration of 10 nM inhibition by ω‐CgTx was reversible, but at higher concentrations blockade was always irreversible. Although current inhibition by nifedipine was maximal at 1μM, supramaximal concentrations reduced the inhibitory actions of ω‐CgTx in a concentration‐dependent manner. Ca2+ channel currents evoked from a holding potential of ‐50 mV showed no inactivation during 200 ms depolarizations but declined in amplitude with successive depolarizing steps (0.2 Hz). Current amplitudes could be restored by returning the holding potential to ‐80 mV. Currents evoked from ‐50 mV were inhibited by nifedipine and ω‐CgTx to a similar degree as those evoked from ‐80 mV. Our results indicate that undifferentiated SH‐SY5Y cells possess L‐ and N‐type Ca2+ channels which can be distinguished pharmacologically but cannot be separated by using depolarized holding potentials. Furthermore, these data suggest that nifedipine has a novel action to inhibit blockade of N‐type channels by ω‐CgTx.
Electrophysiological Interactions Between 5‐Hydroxytryptamine and Thyrotropin Releasing Hormone on Rat Hippocampal CA1 Neurons
Authors: Ballerini L. , Corradetti R. , Nistri A. , Pugliese A. M. , Stocca G. 
Published: April 2006

AbstractIntracellular recording from CA1 neurons of the rat hippocampal slice preparation was used to examine the possibility of functional interactions between 5‐hydroxytryptamine (5‐HT) and thyrotropin releasing hormone (TRH), which act as cotransmitters in other areas of the central nervous system. 5‐HT (30 μM) elicited complex effects consisting of biphasic changes in membrane potential and a strong depression of the afterhyperpolarization (AHP) following a spike burst. TRH (10 μM) did not alter membrane potential or input conductance but it produced a partial block of the AHP. Under single‐electrode voltage clamp, 5‐HT and TRH both reduced the amplitude of voltage‐activated total K+ currents. When the two substances were co‐applied, their actions were occluded. The voltage‐activated K+ current remaining in Ca2+‐free solution lost its sensitivity to 5‐HT and TRH, suggesting that the K+ current modulated by TRH and 5‐HT was Ca2+‐dependent, although TRH itself did not depress high‐threshold voltage‐activated Ca2+ currents. When a relatively small concentration (5 μM) of 5‐HT was co‐applied with an equimolar amount of TRH, the degree of block of the spike AHP was the sum of the two individual effects of these drugs. It is suggested that in hippocampal pyramidal cells 5‐HT and TRH influenced neuronal excitability by depressing a Ca2+‐dependent K+ current, a phenomenon perhaps mediated through a common intracellular second messenger pathway.
Muscarinic Modulation of Intrinsic Burst Firing in Rat Hippocampal Neurons
Authors: Azouz Rony , Jensen Morten S. , Yaari Yoel 
Published: April 2006

AbstractIntracellular recordings in rat hippocampal slices were used to examine how exogenous and endogenous cholinergic agonists modulate the firing pattern of intrinsically burst‐firing pyramidal cells. About 24% of CA1 pyramidal cells generated all‐or‐none, high‐frequency bursts of fast action potentials in response to intracellular injection of long positive current pulses. Application of carbachol (5 μM) converted burst firing in these neurons into regular trains of independent spikes. Acetylcholine (5 μM) exerted a similar effect, provided acetylcholine esterase activity was blocked with neostigmine (2 μM). Atropine (1 μM) reversed this cholinergic effect, indicating its mediation by muscarinic receptors. Cholinergic agonists also caused mild neuronal depolarization but the block of intrinsic burst firing was independent of this effect. Repetitive stimulation of cholinergic fibres in the presence of neostigmine (2 μM) evoked a slow cholinergic excitatory postsynaptic potential (EPSP) lasting about a minute. During the slow EPSP, burst firing could not be evoked by depolarizing pulses and the neurons fired in regular mode. These effects were prevented by pretreatment with atropine (1 μM). Exogenously applied cholinergic agonists and endogenously released acetylcholine also reduced spike frequency accommodation and suppressed the long‐duration afterhyperpolarization in burst‐firing pyramidal cells in an atropine‐sensitive manner. A membrane‐permeable cAMP analogue (8‐bromo‐cAMP; 1 mM) also reduced frequency accommodation and blocked the long‐duration afterhyperpolarization, but did not affect intrinsic burst firing at all. Taken together, the data show that muscarinic receptor stimulation transforms the stereotyped, phasic response of burst‐firing neurons into stimulus‐graded, tonic discharge.
Depth Perception in Monocularly Deprived Cats Following Part‐time Reverse Occlusion
Authors: Mitchell Donald E. , Ptito Maurice , Lepore Franco 
Published: April 2006

AbstractThe behavioural effects of an early period of monocular deprivation can be extremely profound. However, it is possible to achieve a high degree of recovery, even to normal levels of visual acuity, by prompt imposition of certain regimes of part‐time reverse occlusion where the initially non‐deprived eye is occluded for only part of each day in order to allow a daily period of binocular visual exposure. In this paper we report on the depth perception of five monocularly deprived cats that had recovered normal visual acuity in both eyes following imposition of certain of the above occlusion regimes. Although three of the animals exhibited five‐to sevenfold superiority of binocular over monocular depth thresholds, subsequent tests made on two of the animals revealed that they were unable to make stereoscopic discriminations with random‐dot stereograms. Despite the recovery of normal visual acuity in both eyes, we conclude that these animals recover at best only local stereopsis.
Cortical Cells That Migrate Beyond Area Boundaries: Characterization of an Early Neuronal Population in the Lower Intermediate Zone of Prenatal Rats
Authors: DeDiego Isabel , Smith‐Fernández Anibal , Fairén Alfonso 
Published: April 2006

AbstractStudies of the early development of the mammalian cerebral cortex have revealed that the earliest generated neurons that form the primordial plexiform layer (also called preplate or marginal zone) distribute among layer I and layer VII (subplate). By means of bromodeoxyuridine labelling of cells becoming postmitotic, we have found evidence that, in the rat, an additional group of neurons of the primordial plexiform layer remains in the close vicinity of the ventricular zone. This finding, in line with the proposal by Marín‐Padilla (Z Anat. Entwicklungsgesch., 134, 117‐145, 1971), implies that the primordial plexiform layer suffers a tripartition after the formation of the cortical plate and of the intermediate zone (the latter soon becomes the embryonic white matter). Thus, primordial plexiform layer derivatives are in layer I, layer VII (subplate) and in the lower part of the embryonic white matter. This early generated neuronal population is also revealed with an antibody that recognizes the larger (67 kDa) isoform of glutamic acid decarboxylase (Kaufman et al., Science, 232, 1138‐1140, 1986). This is in accord with the earlier finding of a GABA‐containing cell population showing a similar spatiotemporal distribution. The early generated neurons of the embryonic white matter migrate tangentially and, in early postnatal animals, are found as interstitial cells in the medial regions of the subcortical white matter and at the midline in the corpus callosum. At caudal levels, similar cells invade the subpyramidal strata of the developing hippocampus. This tangential migration might explain the tangential dispersion of neural cell clones described in recent studies of cell lineage in the cerebral cortex.
Membrane Properties of Physiologically Classified Rat Dorsal Horn Neurons In Vitro: Correlation with Cutaneous Sensory Afferent Input
Authors: Lopez‐Garcia J. A. , King A. E. 
Published: April 2006

AbstractDorsal horn neurons in the young rat spinal cord‐hindlimb preparation were physiologically classified as wide dynamic range (WDR), nociceptive specific (NS) or low threshold (LT) according to their excitatory responses to low and high intensity mechanical stimuli applied to the hindlimb skin. Two additional types were classified: neurons displaying only sub‐threshold excitations (SUB) and neurons displaying inhibitory events (INH), such as inhibitory post‐synaptic potentials or interruption of spontaneous spiking following cutaneous stimulation. Direct intracellular current injection revealed four different patterns of spiking behaviour: group A neurons were characterized by tonic firing in response to depolarizing current pulses; group B neurons were strongly phasic, producing only one spike at the beginning of the pulse; group A‐B neurons generated an early unsustained (< 300 ms) burst of spikes; and group C neurons exhibited anomalous rectification in response to hyperpolarizing current which was followed by a voltage‐dependent rebound excitation. A statistically significant (P≤ 0.01) association existed between a neuron's physiological classification and its electrophysiological profile. The majority of WDR neurons responded with tonic firing and were assigned to group A, while NS neurons were strongly represented in group A‐B. All INH neurons were assigned to group C. LT neurons were distributed between groups A and A‐B, and SUB neurons were distributed between groups A and B. These data indicate, firstly, that dorsal horn neurons possess heterogeneous membrane properties and, secondly, that a relationship exists between a neuron's biophysical profile and its excitatory or inhibitory response to peripheral cutaneous afferent stimulation. The implications for dorsal horn somatosensory processing are discussed.
Membrane Arachidonic Acid Concentration Correlates with Age and Induction of Long‐term Potentiation in the Dentate Gyrus in the Rat
Authors: Lynch M. A. , Voss K. L. 
Published: April 2006

AbstractWe examined the induction and maintenance of long‐term potentiation (LTP) in vivo in the dentate gyrus of 4‐month‐old and 22‐month‐old urethane‐anaesthetized rats. High‐frequency stimulation of the perforant path induced an immediate increase in the slope of the population excitatory postsynaptic potential (EPSP), which was sustained in the 4‐month‐old animals for the duration of the experiment (45 min post‐tetanus). In the 22‐month‐old group, the mean slope of the population EPSP decreased almost to baseline by the end of the experiment. Examination of the individual records indicated that LTP was sustained for the duration of the experiment in half of the 22‐month‐old animals, while in the others only post‐tetanic potentiation was observed. Membrane arachidonic acid concentration was reduced in aged compared with young animals and was lowest in the subgroup of aged animals which failed to sustain LTP. Potassium‐stimulated, calcium‐dependent release of glutamate was also decreased in aged compared with young animals, but LTP was associated with an increase in glutamate release in the 4‐month‐old group and 22‐month‐old subgroup in which LTP was successfully sustained; no change was observed in the 22‐month‐old group in which LTP was not sustained. The results indicate a correlation between membrane arachidonic acid concentration, glutamate release and ability to sustain LTP in aged animals.
Axons Regenerate with Correct Specificity in Horizontal Slice Culture of the Postnatal Rat Entorhino‐hippocampal System
Authors: Li D. , Field P. M. , Yoshioka N. , Raisman G. 
Published: April 2006

AbstractWe have used slice culture of the entorhino‐hippocampal system to investigate (1) whether nerve fibres which are cut postnatally are able to regenerate and (2) whether the regenerating fibres are able to establish correct selective target specificity in the formation of their terminal fields. Slices of tissue were taken in the horizontal plane through the caudo‐ventral pole of the cerebral hemisphere of 9‐ to 10‐day‐old rats. Such slices maintain the entorhinal cortex in continuity with the hippocampus and intervening retrohippocampal areas. However, because of the dorsal inclination of the entorhino‐hippocampal projection fibres in situ, the segments of the entorhinal cortex and hippocampus contained within each individual horizontal slice were disconnected from each other. During subsequent culture, the formation of fibre connections between the entorhinal area and the hippocampal complex was studied by the extracellular and intracellular anterograde transport of biocytin or biotin dextran, the retrograde transport of biotin dextran or carbocyanine dyes, and by electrical stimulation and recording. For the first 24 h after taking the slice, there were no entorhinal projections beyond the deep white matter, and no fibres reached the hippocampus or dentate gyrus. After 3 days in culture a small number of growing fibres had perforated the subiculum and entered the target areas. Between 6 and 14 days these projections increased and matured. As in the normal adult brain, entorhinal layer II stellate cells projected correctly to the dentate gyrus and hippocampal field CA3, whereas layer III pyramidal cells projected to hippocampal field CA1 and the subiculum. The new fibres grew along both alvear and perforant pathways. Anterograde and retrograde labelling showed that the reciprocal projections from the pyramidal cells of the subiculum and CA1 to the entorhinal area had also been severed at the time of taking the slices, and had similarly regenerated. Our results demonstrate that by taking tissue slices in appropriate planes it is possible to study the regeneration of axons in the tissue environment through which they normally run. This approach avoids the use of coculture and the concomitant difficulties associated with the need for fibres to cross a coculture interface. In horizontal slices of postnatal tissue, severed fibre projections between the entorhinal cortex and the hippocampal complex can regenerate in both directions and re‐establish their correct laminar, pathway and target specificity.