bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acetorphan, an Enkephalinase Inhibitor, Modulates Dopaminergic Transmission in Rat Olfactory Tubercle, but not in the Nucleus Accumbens and Striatum
Authors: Dourmap Nathalie , Michael‐Titus Adina , Costentin Jean 
Published: April 2006

AbstractThe present study focused on the effects of acetorphan, a parenterally active enkephalinase inhibitor, on dopaminergic transmission in rat olfactory tubercle, nucleus accumbens and striatum. Acetorphan was administered i.v. (10 mg/kg) 15 min before measurement of the in vivo specific binding of [3H]N‐propyl‐norapomorphine ([3H]NPA) or measurement of the levels of dopamine (DA) and its metabolites 3‐methoxytyramine‐homovanillic acid (3MT‐HVA) in the three areas. Acetorphan decreased the in vivo specific binding of [3H]NPA in the olfactory tubercle, this effect being antagonized by naloxone 1.5 mg/kg s.c. DA release in this brain structure was also significantly increased by acetorphan 10 mg/kg, as indicated by the 3MT:DA and HVA:DA ratios. Neither the specific binding of [3H]NPA nor DA metabolism and release were modified by the inhibitor in the striatum and the nucleus accumbens. The stimulant effect of acetorphan was significantly decreased in rats in which a bilateral lesion of dopaminergic endings in the olfactory tubercle had been produced by 6‐hydroxydopamine (6‐OHDA). These results suggest that dopaminergic transmissions in the olfactory tubercle are particularly sensitive to the modulation exerted by endogenous enkephalins, this modulation being at least partly involved in the increased locomotion induced by the enkephalinase inhibitor.
Dopaminergic Modulation of Transient Neurite Outgrowth from Horizontal Cells of the Fish Retina is not Mediated by cAMP
Authors: Kohler Konrad , Weiler Reto 
Published: April 2006

AbstractHorizontal cell dendrites invaginating the cone pedicles in the fish retina exhibit a marked light dependent plasticity in the morphology of their synaptic connections. Upon light adaptation of the retina, numerous spinules are formed which disappear during dark adaptation. This process is paralleled by a strengthening and weakening, respectively, of the horizontal cell's inhibitory output. The formation of spinules during light adaptation requires dopaminergic activity as it does not occur in dopamine‐depleted retinas, but can be partially induced in depleted retinas by the exogenous administration of dopamine. Although horizontal cells do have D1 receptors the action of dopamine is not coupled to a stimulation of cAMP. An increase of intracellular cAMP either by injection of a cAMP analogue or by metabolic interference does not result in any spinule formation. The data suggest that dopamine must act through a cAMP independent intracellular mechanism.
Evidence that Very Slow Wallerian Degeneration in C57BL/Ola Mice is an Intrinsic Property of the Peripheral Nerve
Authors: Perry V. H. , Brown M. C. , Lunn E. R. , Tree P. , Gordon S. 
Published: April 2006

AbstractWe have described a mutant mouse, C57BL/Ola, in which Wallerian degeneration following peripheral nerve transection is very slow. Our previous results suggested that recruited monocytes play a role in rapid Wallerian degeneration. The nature of the mutation in C57BL/Ola mice is not known and we have investigated whether the defect is intrinsic to the nerve or due to a defect in the circulating monocytes. We have made chimaeric mice in which bone marrow from histocompatible mice, with rapidly degenerating nerves and normal monocyte recruitment, was used to reconstitute irradiated C57BL/Ola mice and vice‐versa. A substantial degree of donor repopulation of the hosts was confirmed by measures of the levels of glucose‐phosphate isomerase alloenzymes in blood and tissue samples from the two different strains. The rate of degeneration of the transected sciatic nerve was found to be host‐dependent, providing evidence that the mutation affects cell populations intrinsic to the nerve and not the circulating monocytes. We provide additional evidence that the peripheral nerves of C57BL/Ola mice are different from those of other mice as they degenerate at a slower rate in vitro.
Transferrin Receptor Expression and Iron Uptake in the Injured and Regenerating Rat Sciatic Nerve
Authors: Raivich G. , Graeber M. B. , Gehrmann J. , Kreutzberg G. W. 
Published: April 2006

AbstractIron‐saturated transferrin is a ubiquitous growth factor that plays a critical role in cellular iron uptake, growth and proliferation. Here we have studied the expression and distribution of transferrin receptors and iron uptake following injury of the rat sciatic nerve. Axotomy led to a massive but transient increase (days 2–9, maximum day 4) in [125l]transferrin binding at the site of the injury and in the distal, denervated part of the crushed or resected sciatic nerve, shortly preceding the time course of cellular proliferation (Friede and Johnstone, Acta Neuropathol, 7, 218–231, 1967; Jurecka et al., Acta Neuropathol, 32, 299–312, 1975). An additional, transient increase in specific binding was observed during reinnervation after reconnection of the resected sciatic nerve. Immunocytochemistry using the Ox‐26 monoclonal antibody revealed strong and simultaneous expression of the transferrin receptor protein on two different cell types: on a subpopulation of blood‐borne macrophages invading the injured peripheral nerve and on Schwann cells reacting to denervation and reinnervation. In addition, studies using intravenously injected radioactive iron (59Fe3+) showed a massive increase in endoneural iron uptake confined to the lesion site and to the distal part of the axotomised sciatic nerve, parallel to the time course of reactive transferrin receptor expression. Since iron is an essential cofactor of a number of key enzymes needed in energy metabolism and DNA synthesis, these data suggest that the induction of transferrin receptor expression may play an important role in the regulation of cellular growth and proliferation during peripheral nerve regeneration.
Striatal Ascorbate and its Relationship to Dopamine Receptor Stimulation and Motor Activity
Authors: Zetterström Tyra , Wheeler David B. , Boutelle Martyn G. , Fillenz Marianne 
Published: April 2006

AbstractWe have used the techniques of microdialysis and in vivo voltammetry to monitor striatal dopamine and ascorbate, as well as motor activity in unanaesthetized, freely‐moving rats. Systemic administration of the non‐selective dopamine receptor agonist apomorphine (0.5 mg/kg, s.c.) caused a decrease in dopamine, an increase in ascorbate, stereotyped behaviour and a generalized increase in motor activity. Separate systemic applications of the D2 receptor agonist SKF 38393 (10 mg/kg, s.c.) and the D2 receptor agonist Quinpirole (0.1 mg/kg s.c.) caused a decrease in dopamine but had no effect on ascorbate or motor activity. After coadministration of these drugs, there was an increase in both ascorbate and motor activity. Local application of apomorphine (0.01 mM) caused a reduction in dopamine similar to that seen following systemic application but had no effect on ascorbate or motor activity. The present results demonstrate that dopamine, via D1 and D2 receptors outside the striatum, plays an important role in the control of ascorbate release. These results lend further support to the hypothesis that changes in ascorbate levels are an index of glutamatergic neurotransmission.
The Effects of Activation or Inhibition of the Subthalamic Nucleus on the Metabolic and Electrophysiological Activities Within the Pallidal Complex and Substantia Nigra in the Rat
Authors: Féger Jean , Robledo Patricia 
Published: April 2006

AbstractThe changes in local cerebral glucose utilization (LCGU) and neuronal unit activities in the subthalamic nucleus and its major target structures (the pars reticulata of the substantia nigra, the globus pallidus and the entopeduncular nucleus) following microinjection of a GABAergic antagonist (bicuculline methiodide, 0.08 nmol) or agonist (muscimol, 0.2 nmol) into the subthalamic nucleus were determined. The metabolic effect was assessed by measuring LCGU by quantitative [14C]‐2‐deoxyglucose autoradiography in ketamine‐anaesthetized rats. Bicuculline methiodide induced increased LCGU in the ipsilateral globus pallidus, the entopeduncular nucleus and the substantia nigra pars reticulata. In contrast, muscimol decreased LCGU in these structures. The neuronal activities in the subthalamic nucleus and related structures increased following injection of bicuculline and decreased after injection of muscimol. The changes in LCGU within the structures directly related to the subthalamic nucleus were correlated with the changes in the unit activity either in the subthalamic nucleus and/or its projection structures. However, the amplitude of the relative changes in neuronal unit activity were greater than the changes in LCGU. Nevertheless, the results emphasize the functional role of the subthalamic nucleus as an activating structure within the basal ganglia.
Excitatory Actions of the Metabotropic Excitatory Amino Acid Receptor Agonist, trans‐(±)‐1‐amino‐cyclopentane‐1,3‐dicarboxylate (t‐ACPD), on Rat Thalamic Neurons In Vivo
Authors: Salt T. E. , Eaton S. A. 
Published: April 2006

AbstractThe metabotropic excitatory amino acid receptor agonist trans‐(±)‐1‐amino‐cyclopentane‐1,3‐dicarboxylate (t‐ACPD) was applied to rat ventrobasal thalamic neurons by iontophoresis. This agonist typically evoked an excitatory response which was slower in onset and of longer duration than responses to the other excitatory amino acid agonists, N‐methyl‐aspartate, kainate or (R.S)‐a‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate. Responses to f‐ACPD were resistant to the excitatory amino acid antagonists 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione, 3‐((RS)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid and kynurenate. These results suggest that f‐ACPD may exert its effects via the so‐called ‘metabotropic’ excitatory amino acid receptor. The putative antagonists at this receptor, D‐2‐amino‐4‐phosphono‐butyrate (D‐AP4), L‐2‐amino‐4‐phosphono‐butyrate (L‐AP4) and L‐2‐amino‐3‐phosphono‐propionate (L‐AP3), were able to reduce responses to t‐ACPD under certain circumstances. However, such antagonism was always accompanied by similar reductions in excitatory responses to other agonists. These non‐selective effects would appear to limit the usefulness of AP4 and AP3 as antagonists of t‐ACPD.
Dorsal Horn Plasticity Following Re‐routeing of Peripheral Nerves: Evidence for Tissue‐Specific Neurotrophic Influences from the Periphery
Authors: Lewin Gary R. , McMahon Stephen B. 
Published: April 2006

AbstractSome properties of primary sensory neurons change when they reinnervate new peripheral targets (McMahon et al., Neuroscience, 33, 67–75, 1989). We ask here if such influences can extend to the central connectivity of sensory neurons. In adult rats the nerve to the gastrocnemius muscle (GN) and the cutaneous sural nerve (SN) were self‐ and cross‐anastomosed on left‐ and right‐hand sides, respectively, so that they regenerated to either appropriate or inappropriate targets. Ten to 14 weeks later, the distribution and strength of spinal connections of the SN and GN were determined. The unmyelinated afferents in the GN innervating skin increased their connectivity to 286% of that seen for the GN innervating muscle (P < 0.005), and came to resemble normal cutaneous afferents. However, for the SN there was no significant difference between appropriately and inappropriately regenerated nerves by this measure. The ability of myelinated fibres to produce inhibitions and facilitations in dorsal horn cells was also assessed. The intact or self‐anastomosed SN produced predominantly inhibitory effects, whilst the GN produced predominantly facilitatory effects. After the SN had regenerated to muscle its central effects became predominantly facilitatory, whilst those of the GN innervating skin became inhibitory. These changes were statistically significant. In conclusion, we have found that major changes in the physiology of central connections in the dorsal horn may occur following peripheral reinnervation of foreign targets. The changes that were seen were appropriate to the new target, and could not easily be explained by non‐specific changes due to axotomy, or changes in A‐fibre‐mediated inhibitions. We suggest that these effects might arise because of trophic influences arising in and specific to different peripheral targets.
GABA‐Mediated Presynaptic Inhibition in Crayfish Primary Afferents by Non‐A, Non‐B GABA Receptors
Authors: El Manira A. , Clarac F. 
Published: April 2006

AbstractGABAergic presynaptic inhibition has been investigated in primary afferents using an in vitro preparation of the crayfish, Procambarus clarkii. Presynaptic terminals of a leg proprioceptor, the coxo‐basal (CB) chordotonal organ, were impaled in the neuorpil of the 5th thoracic ganglion. Pressure ejection of small volumes of the GABAA or GABAB receptor agonists, muscimol and 3‐aminopropylphosphinic acid (3‐APA), both induce depolarizing responses in the impaled CB sensory terminal. These depolarizations are not blocked by the specific GABAA and GABAB receptor antagonists, SR‐95531 and phaclofen, but they are abolished by picrotoxin. Both muscimol‐ and 3‐APA‐induced depolarizations are carried by an increase in conductance to Cl‐. The presynaptic increase in conductance to C1‐ by GABA receptor activation leads to a depression of sensory synaptic transmission through a shunting of the incoming spikes. Monosynaptic EPSPs elicited in motor neurons by CB sensory nerve stimulation are depressed by muscimol and 3‐APA. GABA‐mediated presynaptic modulation occurs in crayfish primary afferents which can adjust the gain of reflexes. These results show that GABA‐activated Cl‐ channels can induce a modulation of synaptic transmission, but also that the distinction between GABAA and GABAB receptors, as in vertebrates, is not applicable to the crustacean primary afferents.
Activation of AP5‐sensitive NMDA Receptors is Not Required to Induce LTP of Synaptic Transmission in the Lateral Perforant Path
Authors: Bramham Clive R. , Milgram N. W. , Srebro Bolek 
Published: April 2006

AbstractThe role of the N‐methyl‐D‐aspartate (NMDA) type of glutamate receptor in long‐term potentiation (LTP) of the medial (MPP) and lateral (LPP) divisions of the perforant path‐granule cell system was investigated in urethane‐anaesthetized rats. A stimulating electrode was positioned in the dorsomedial or ventrolateral aspect of the angular bundle for selective activation of either the MPP or LPP, respectively. A push‐pull cannula served to focally perfuse artificial cerebrospinal fluid (ACSF) across the perforant path synaptic zone, while evoked potentials were monitored in the dentate hilus. Identification of LPP and MPP responses was based on (1) differences in population excitatory postsynaptic potential (EPSP) waveform obtained during stimulus depth profiles, and (2) differential sensitivity of evoked EPSPs to the glutamate receptor agonist L‐aminophosphonobutyrate (AP4), and the antagonist γ‐D‐glutamylglycine (DGG). High‐frequency stimulation (400 Hz, 8 bursts of 8 pulses) applied to the lateral and medial perforant path elicited LTP of the EPSP and population spike in rats perfused with standard medium. In the MPP, LTP was almost completely blocked when D‐aminophosphonopentanoate (AP5; 100 μM), a selective NMDA receptor antagonist, was perfused during the tetanus. Surprisingly, in the LPP experiments, AP5 did not impair induction of the ‘synaptic’ EPSP component of LTP. This occurred despite the ability of AP5 to block LTP of the LPP evoked population spike. The results suggest the existence of a novel, NMDA receptor‐independent form of synaptic LTP in the lateral perforant path.
Learning‐induced Increase of Immediate Early Gene Messenger RNA in the Chick Forebrain
Authors: Anokhin Konstantin V. , Rose Steven P. R. 
Published: April 2006

AbstractThe immediate early genes c‐fos and c‐jun are activated rapidly in nerve cells in response to in vivo and in vitro stimulation. Because of their involvement in transcriptional regulation, the products of these genes have been proposed as nuclear signals for consolidation of long‐term memory. However, no specific changes of immediate early gene expression in relation to learning have yet been reported. Compared with quiet controls, training young chicks to discriminate food grains from inedible pebbles results in a 4.8‐fold elevation of c‐fos and a 3.7‐fold elevation of c‐jun mRNA in the forebrain 30 min after an 8‐min training session. Compared to chicks that had learned the discrimination and were merely repeating already learned behaviour, the increase in c‐jun mRNA in the learning group was 64% (P < 0.03) but a 24% increase in c‐fos mRNA was not significant. Because the increased expression is higher in birds that are learning the task than in those that are repeating already learned behaviour, and is not proportional to behavioural activity per se, we conclude that learning a new task is itself responsible for enhanced expression of the genes.
Effect of Climbing Fibre Deprivation on the K+‐evoked Release of Endogenous Adenosine from Rat Cerebellar Slices
Authors: Do Kim Quang , Vollenweider Franz X. , Zollinger Markus , Cuénod Michel 
Published: April 2006

AbstractWe report the identification of a compound whose K+‐induced Ca2+‐dependent release in rat cerebellar slices was reduced following climbing fibre deprivation by 3‐acetylpyridine8 (3‐AP) treatment. Based on HPLC retention time, UV absorption spectrum, and mass spectrometry, this compound was identified as adenosine. The K+‐induced, Ca2+‐dependent release of adenosine was subsequently quantified in control and 3‐AP‐treated rats. It decreased by 60–70% in both the cerebellar vermis and hemispheres following climbing fibre deprivation, while 3‐AP treatment had no effect on adenosine release in the cerebral cortex. Inhibition of ecto‐5′‐nucleotidase by α,β‐methylene ADP and GMP decreased basal and stimulated efflux of adenosine in the cerebellum by 50–60%, indicating that a Significant proportion of adenosine was derived from the extracellular metabolism of released nucleotides. Taken with the reports of other groups on adenosine in cerebellum, these results suggest that climbing fibre activity increases the extracellular level of adenosine, probably through the metabolism of released nucleotides. This adenosine could then cause presynaptic inhibition of the release of the parallel fibre transmitter, which is presumably glutamate. This may account for the climbing fibre‐evoked depression of Purkinje cell sensitivity to parallel fibre input.
Cerebral Glycoprotein Synthesis and Long‐term Memory Formation in the Chick (Gallus domesticus) Following Passive Avoidance Training Depends on the Nature of the Aversive Stimulus
Authors: Bourne R. C. , Davies D. C. , Stewart M. G. , Csillag A. , Cooper M. 
Published: April 2006

AbstractChicks that peck a small bright bead coated in a distasteful substance can learn in a single trial to subsequently avoid a similar bead. The taste aversant commonly used is methyl anthranilate, which also has a strong pervasive odour. We have compared the efficacy of methyl anthranilate and the apparently odourless quinine as aversants. Methyl anthranilate‐trained chicks learnt the task and the memory apparently persisted undiminished for at least 24 h. Quinine‐trained chicks exhibited a memory for the task similar to that of methyl anthranilate‐trained chicks 45 min after training, this thereafter declined until, at 24 h after training, they showed no recall. We investigated the incorporation of a radio‐labelled synaptic membrane glycoprotein precursor, [3H]fucose, into three regions of the chick forebrain; two of these regions have previously been implicated in learning using methyl anthranilate as the aversant. There was a significant increase in [3H]fucose incorporation into the left lateral cerebral area and numerically similar, but nonsignificant, increases in the intermediate part of the medial hyperstriatum ventrale and lobus parolfactorius. There were no such increases in the right hemisphere of methyl anthranilate‐trained chicks or any region of either hemisphere of quinine‐trained chicks. Thus, the memory for methyl anthranilate is longer‐lasting than that for quinine and is associated with increased fucosylation in the left cerebral hemisphere and although in the short‐term, chicks can retain a memory of the one‐trial passive avoidance task with quinine as the aversant, this does not result in a localized increase in cerebral [3H]fucose incorporation.
Descending Projections from the Substantia Nigra and Retrorubral Field to the Medullary and Pontomedullary Reticular Formation
Authors: Von Krosigk M. , Smith A. D. 
Published: April 2006

AbstractWe have investigated the projection from the substantia nigra to the pontomedullary reticular formation in the rat using both retrograde and anterograde neuroanatomical tracers. Injections of a conjugate of wheatgerm agglutinin with horseradish peroxidase into the medullary or pontomedullary reticular formation resulted in the retrograde labelling of a continuous band of cells extending from the caudal half of the dorsolateral substantia nigra into the retrorubral field. Injections of the anterograde tracer Phaseolus vulgaris leukoagglutinin (PHA‐L) into either the dorsolateral substantia nigra or the caudally adjacent retrorubral field revealed a descending projection to the lateral medullary and pontomedullary brainstem, which terminated mainly within the lateral (parvicellular) reticular formation. The anterograde PHA‐L fibre labelling ran throughout the rostrocaudal extent of the parvicellular reticular formation and extended into the caudally continuous region, the medullary dorsal and medullary ventral reticular formation, where it tapered off. Also labelled, although more lightly, were the rostral and ventrolateral regions of the nucleus of the solitary tract and the magnocellular reticular formation. Electron microscopy established that the PHA‐L‐labelled fibres formed synaptic contacts with nerve cell bodies and dendrites in the parvicellular reticular formation. It is suggested that one role of this nigroreticular pathway might be to connect the basal ganglia with brainstem premotor neurons that influence orofacial musculature.
C‐fibre Function During the 6 Weeks Following Brief Application of Capsaicin to a Cutaneous Nerve in the Rat
Authors: Pini Adrian , Lynn Bruce 
Published: April 2006

AbstractThe functional properties of afferent fibres, especially C‐fibres, have been studied over the 46 days following application of capsaicinoids to a segment of the saphenous nerve in the rat. After 1–3 days, approximately half of the C‐afferents were found to be non‐conducting at or immediately distal to the treatment site. By 6–9 days there was some recovery of conduction at the treatment site, but few of the conducting fibres were excitable from the skin. From 12 days onwards, C‐fibre conduction in the segment of nerve both proximal and distal to the treatment site was reduced and of the conducting fibres relatively few had cutaneous receptive fields. In the sample of C‐fibres with cutaneous receptive fields the proportion of polymodal nociceptors was reduced markedly compared with control values. Analysis of the numbers of surviving units shows a large effect on C‐polymodal nociceptors, but no significant change in the numbers of any other type of afferent unit. At 2 weeks, when C‐fibre numbers were reduced to about one third, there was a virtual abolition of antidromic vasodilatation and an 85% fall in skin substance P levels. The synthetic capsaicinoid, NE‐21610, had similar actions to capsaicin and was more potent in depleting skin substance P levels. These results confirm that capsaicinoids produce a selective local lesion on nociceptive C‐fibres in rat cutaneous nerves. In addition, the transient and partial nature of functional recovery indicates that capsaicin may also cause a longer‐term toxic action that inhibits significant regeneration.