bluuebunny/crossref_metadata_2025 huggingface dataset:
Oscillatory Neuronal Responses in the Visual Cortex of the Awake Macaque Monkey
Authors: Kreiter A. K. , Singer W.
Published: April 2006

An important step in early visual processing is the segmentation of scenes. Features constituting individual objects have to be grouped together and segregated from those of other figures or the background. It has been proposed that this grouping could be achieved by synchronizing the fine temporal structure of responses from neurons excited by an individual figure. In the cat visual cortex evidence has been obtained that responses of feature‐selective neurons have a distinctive oscillatory structure and can synchronize both within and across cortical areas, the synchronization depending on stimulus configuration. Here we investigate the generality of oscillatory responses and their synchronization and specifically whether these phenomena occur in extrastriate areas of the visual cortex of the awake behaving primate. We find in the caudal superior temporal sulcus of the macaque monkey (Macaca fascicularis) that adjacent neurons can synchronize their responses, in which case their discharges exhibit an oscillatory temporal structure. During such periods of local synchrony spatially separated cell groups can also synchronize their responses if activated with a single stimulus. These findings resemble those described previously for the cat visual cortex, except that in the awake monkey the oscillatory episodes tend to be of shorter duration and exhibit more variability of oscillation frequency.
Striatal c‐fos Induction by Cocaine or Apomorphine Occurs Preferentially in Output Neurons Projecting to the Substantia Nigra in the Rat
Authors: Cenci M. Angela , Campbell Kenneth , Wictorin Klas , Björklund Anders
Published: April 2006

Fluorogold or rhodamine‐labelled latex beads were injected in the substantia nigra (SN) or the globus pallidus (GP) in order retrogradely to label striatal output neurons that project to the two target structures. Ten days later, striatal c‐fos was induced by systemic administration of cocaine (five normal rats; 25 mg/kg cocaine i.p. 2 h before killing) or apomorphine (five unilaterally dopamine‐denervated rats; 0.25 mg/kg apomorphine s. c. 2 h before killing), and detection of the Fos protein in the striatum was achieved by immunofluorescence. Sections through the caudate‐putamen that displayed good labelling from both SN and GP were selected for a quantitative analysis: the number of retrogradely labelled cells that exhibited Fos immunoreactivity, as well as the total number of retrogradely labelled cells located within a grid (0.16 mm2 in size) were counted manually at 25 x magnification. Cocaine induced a proportionally higher c‐fos expression in striate‐nigral compared to striate‐pallidal neurons, whereas apomorphine activated Fos almost exclusively in striate‐nigral neurons. The present findings are consistent with the idea that striatal c‐fos induction by dopaminergic agents is primarily mediated by an interaction with D1 ‐receptors, which are thought to be selectively localized on neurons projecting to SN.
Amnesia for Complex Naturalistic Scenes and for Objects Following Fornix Transection in the Rhesus Monkey
Authors: Gaffan D.
Published: April 2006

Rhesus monkeys (Macaca mulatta) were trained to discriminate among many complex naturalistic scenes. The scenes were still frames from a cinema film. They were presented as the discriminative stimuli in a concurrent discrimination learning task in which each discriminative stimulus was presented on one trial each day. Learning of this task was severely impaired by fornix transection. The same animals were also deficient in a similar concurrent discrimination learning task, with each discriminative stimulus presented on one trial each day, but with objects, not complex scenes, as the stimulus material. The impairment in object discrimination learning in the present experiment is attributable to an interaction of object discrimination learning with scene discrimination learning, and can be understood as an effect of interference in long‐term memory. In contrast to these impairments in long‐term memory, a test of within‐session learning of complex scenes, in which the average interval between successive presentations of the same stimulus was <3 min, was performed without significant impairment by the fornix‐transected animals. These results show that long‐term memory for complex naturalistic scenes reveals analogues in the monkey of human episodic memory and its impairment in amnesia.
Modulation by NMDA Receptor Antagonists of Glycine Receptor Isoform Expression in Cultured Spinal Cord Neurons
Authors: Hoch W. , Betz H. , Schramm M. , Wolters I. , Becker C. M.
Published: April 2006

Two developmentally regulated isoforms of the inhibitory glycine receptor harbouring different α subunit variants, GlyRN (neonatal) and GlyRA (adult), have previously been identified in rodent spinal cord. Primary cultures of embyronic spinal neurons, however, express predominantly GlyRN. Here, N‐methyl‐d‐aspartate (NMDA) receptor antagonists were found to significantly increase glycine receptor levels in mouse spinal cord cultures. In the presence of 2‐amino‐5‐phosphonovalerate or MK‐801 (dizocilpine), both GlyRN and GlyRA contents were elevated, as revealed by isoform‐selective immunoassays and amplification of corresponding α subunit transcripts by the polymerase chain reaction. This effect of NMDA receptor antagonists was restricted to a ‘sensitive’ period within the second week after plating. Apparently, NMDA receptor‐mediated glutamate neurotoxicity prevented GlyRA accumulation under standard culture conditions. Our data indicate that neuronal maturation in cell culture depends on conditions which minimize cell death resulting from glutamate release into the culture medium.
Regulation of Neurotrophin mRNA Expression in the Rat Brain by Glucocorticoids
Authors: Barbany Gisela , Persson Håkan
Published: April 2006

Northern blot analysis was used to examine the effects of glucocorticoids on neurotrophin mRNA expression in the rat cerebral cortex and hippocampus. The results show that 3 days after adrenalectomy the mRNA levels for nerve growth factor (NGF), brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3) decreased significantly in both these regions. In adrenalectomized animals given dexamethasone replacement the mRNA levels for the three neurotrophins were restored to control levels. The effect of a single dose of dexamethasone (5 mg/kg) administered i p. to intact animals on the expression of neurotrophins was also examined. NGF and NT‐3 mRNAs showed a 2.5‐fold and a 1.4‐fold increase, respectively, during the first 4 h after the injection. The increase was followed by a decrease, with levels ‐50% of control 24 and 48 h after the injection. In contrast, the level of BDNF mRNA did not change during the first 10 h after the injection, but decreased to 70% of control 48 h after the injection. These data indicate that glucocorticoids regulate neurotrophin mRNA expression both in the cortex and in the hippocampus, and suggest further that the known effects of glucocorticoids on neuronal survival in the brain could be due to changes in the levels of neurotrophins in the brain.
Role of Dopaminergic D2 Receptors in the Regulation of Glutamic Acid Decarboxylase Messenger RNA in the Striatum of the Rat
Authors: Caboche Jocelyne , Vernier Philippe , Rogard Monique , Julien Jean‐François , Mallet Jacques , Besson Marie‐Jo
Published: April 2006

Levels of messenger RNA (mRNA) encoding glutamic acid decarboxylase (GAD) and preproenkephalin (PPE) were measured by Northern blot and in situ hybridization analyses in the striatum of the rat, after chronic injections of two neuroleptics, sulpiride and haloperidol. The Northern blot analysis showed that the chronic injection of sulpiride at high doses (80 mg/kg, twice a day, 14 days) increased striatal GAD and PPE mRNA levels by 120% and 78% respectively, when compared to vehicle‐injected rats. Haloperidol injections at relatively low doses (1 mg/kg, once a day, 14 days) produced parallel increases in GAD (40%) and PPE (52%) mRNA levels. After in situ hybridization densitometric measurements were performed on autoradiograms from rats treated with sulpiride, haloperidol or vehicle. The distribution of GAD and PPE mRNA signals in control rats was homogeneous along the rostrocaudal extension of the striatum. A similar increase was found along this axis after sulpiride (20%) and haloperidol (30%) treatments. The cellular observation of hybridization signals showed that grain density for GAD mRNA was increased in a majority of striatal cells after both treatments. By contrast, the PPE mRNA hybridization signal only increased in a subpopulation of neurons. The effects of such treatments were also analysed by measuring GAD activity in the striatum and in its output structures, the globus pallidus and the substantia nigra. After the administration of sulpiride, GAD activity was not modified in the striatum but increased in the globus pallidus (by 17%). After haloperidol treatment, GAD activity was increased in the globus pallidus (20%) and the substantia nigra (17%). It is concluded that the interruption of dopaminergic transmission, more precisely the D2 receptor blockade, promotes in striatopallidal neurons an increase in GAD mRNA accompanied by an increase in GAD activity and PPE mRNA. A possible regulation of GAD mRNA and GAD activity in striatonigral neurons is also discussed.
Expression of Ciliary Neurotrophic Factor and the Neurotrophins – Nerve Growth Factor, Brain‐Derived Neurotrophic Factor and Neurotrophin 3—in Cultured Rat Hippocampal Astrocytes
Authors: Rudge John S. , Alderson Ralph F. , Pasnikowski Elizabeth , McClain Joyce , Ip Nancy Y. , Lindsay Ronald M.
Published: April 2006

Cultured astrocytes are known to possess a range of neurotrophic activities in culture. In order to examine which factors may be responsible for these activities, we have examined the expression of the genes for four known neurotrophic factors – ciliary neurotrophic factor (CNTF), nerve growth factor (NGF), brain‐derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3) – in purified astrocyte cultures derived from neonatal rat hippocampus. Hippocampal astrocytes were found to express mRNA for three neurotrophic factors – CNTF, NGF and NT3 – at significantly higher levels than other cultured cell types or cell lines examined. BDNF messenger RNA (mRNA), however, was undetectable in these astrocytes. The levels of CNTF, NGF and NT3 mRNA in astrocytes were largely unaffected by their degree of confluency, while serum removal caused only a transient decrease in mRNA levels, which returned to basal levels within 48 h. Astrocyte‐derived CNTF was found to comigrate with recombinant rat CNTF at 23 kD on a Western blot. Immunocytochemical analysis revealed strong CNTF immunoreactivity in the cytoplasm of astrocytes, weak staining in the nucleus, but no CNTF at the cell surface. NGF and NT3 were undetectable immunocytochemically. CNTF‐like activity, as assessed by bioassay on ciliary ganglion neurons, was found in the extract of cultured astrocytes but not in conditioned medium, whereas astrocyte‐conditioned medium supported survival of dorsal root ganglion neurons but not ciliary or nodose ganglion neurons. This conditioned medium activity was neutralized with antibodies to NGF. Astrocyte extract also supported survival of dorsal root ganglion and nodose ganglion neurons, but these activities were not blocked by anti‐NGF. Part, but not all, of the activity in astrocyte extracts which sustained nodose ganglion neurons could be attributed to CNTF.
NMDA Receptor‐dependent Transient Homo‐ and Heterosynaptic Depression in Picrotoxin‐treated Hippocampal Slices
Authors: Bashir Zafar I. , Collingridge Graham L.
Published: April 2006

Extracellular recording was used to study the effects of high‐frequency (tetanic) stimulation on excitatory synaptic transmission in the CA1 region of rat hippocampal slices in the presence of the γ‐aminobutyric acid (GABA) type A antagonist, picrotoxin (50 γM). Under these conditions tetanic stimulation (100 Hz, 1 s) at the test intensity resulted in homosynaptic long‐term potentiation (LTP). In contrast, tetanic stimulation of higher intensity (100 Hz, 1 s, double test intensity) resulted in homo‐ and heterosynaptic depression which recovered within 45 min. A transient (1–3 min) negative shift in DC potential and a transient (5–10 min) depression of the homosynaptic fibre volley occurred immediately following the higher intensity tetanus. The DC shift, induction of homo‐ and heterosynaptic depression and depression of the fibre volley were reversibly prevented by the N‐methyl‐d‐aspartate (NMDA) receptor antagonist, d‐2‐amino‐5‐phosphonopentanoate (AP5; 20 γM) but were not prevented by a variety of L‐type calcium channel antagonists. Transient (30 ‐ 45 min) synaptic depression of pharmacologically isolated NMDA receptor‐mediated field excitatory postsynaptic potentials also occurred following tetanic stimulation (100 Hz, 1 s) at double test intensity. These results demonstrate an NMDA receptor‐dependent form of reversible synaptic depression in the CA1 region of the hippocampus.
Memory Formation in Day‐old Chicks Requires NMDA but not Non‐NMDA Glutamate Receptors
Authors: Burchuladze Rusudan , Rose Steven P. R.
Published: April 2006

The non‐competitive N‐methyl‐D‐aspartate (NMDA) antagonist MK‐801, injected intraperitonealy at 0.1 mg/kg, at times between 1 h before and 5 min after training chicks on a one‐trial passive avoidance task, resulted in amnesia for the task on test 3 or 24 h subsequently. No amnesia was apparent at 24 h if chicks were injected between 1 and 6 h after training. Amnesia did not develop immediately; it was not apparent 30 min after training in chicks injected 5 min after training. At this dose of MK‐801 no other effects on motor or pecking behaviour of the birds were observed. Bilateral or unilateral intracerebral injections of 1.5 nM MK‐801 5 min after training produced a similar amnesia at 3 h to that of intraperitonealy injected MK‐801; no hemispheric differences were observed, presumably because of the ready diffusion of the MK‐801. By contrast, intracerebral injections of the non‐NMDA glutamate antagonists 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX), 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX) and 6,7‐nitro‐7‐sulphamoyl‐benzoquinoxaline‐2,3‐dione (NBQX) (0.066 μM) 5 min after training, despite producing severe if transient behavioural disturbances, were without effect on retention for the avoidance response in chicks tested 3 h subsequently. We interpret these results as pointing to a requirement for NMDA, but not kainate or quisqualate, receptor activation as an early enabling event in the biochemical cascade required for long‐term memory formation for passive avoidance in the chick.
Cellular Localization of Brain‐derived Neurotrophic Factor and Neurotrophin‐3 mRNA Expression in the Early Chicken Embryo
Authors: Hallböök Finn , Ibáñez Carlos F. , Ebendal Ted , Persson Håkan
Published: April 2006

Degenerate primers from conserved regions in nerve growth factor, brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3) were used in the polymerase chain reaction to isolate DNA fragments from the chicken BDNF and NT‐3 genes. A genomic clone coding for chicken NT‐3 was isolated and the structure of the chicken NT‐3 mature protein was subsequently deduced from nucleotide sequence analysis of the isolated chicken NT‐3 gene. Comparison of the chicken BDNF and NT‐3 with the corresponding rat molecules showed that the avian molecules are very similar to their mammalian homologues. Northern blot analyses of messenger RNA (mRNA) from chicken embryos from embryonic day 3.5 (E3.5), E4.5, E8, E12 and E18 showed that expression of both BDNF and NT‐3 mRNA peaked at E4.5 and decreased at later stages of development. Both probes revealed two transcripts; larger mRNAs of 4.5 kilobases (kb) for BDNF and 4.0 kb for NT‐3 predominated over the smaller transcripts of 1.4 and 1.3 kb, respectively. The cellular localization of BDNF and NT‐3 mRNA in the E4 and E6 embryos was studied by in situ hybridization. In the E4 embryo, labelling for BDNF was seen over cells in restricted parts of the epithelium of the otic vesicle. Analysis of adjacent sections for the low‐affinity nerve growth factor receptor mRNA showed that regions in the otic vesicle epithelium which labelled for BDNF mRNA also labelled for low‐affinity nerve growth factor receptor mRNA. No labelling for NT‐3 was detected in the otic vesicle. Labelling for BDNF mRNA was also found over mesenchyme dorsal to the wing bud, in the wing bud and in the splanchnopleural lining of the stomach. Labelling for NT‐3 mRNA was found at E4 over the epidermis on the ventral side in the region of the branchial arches. The labelling extended up the maxillary processes to Rathke's pouch. The closely located infundibulum was weakly labelled for NT‐3 mRNA. NT‐3 mRNA was also detected in the mesenchyme surrounding the oesophagus and lung buds. The regional expression pattern is in agreement with the established role for BDNF and NT‐3 as target‐derived neurotrophic factors, but the results also suggest that BDNF may be an intrinsic factor important for the development of the inner ear. The results support the emerging view that neurotrophic factors can play a role in early differentiation of both neuronal and non‐neuronal tissues.
Formation of Specific Efferent Connections in Organotypic Slice Cultures from Rat Visual Cortex Cocultured with Lateral Geniculate Nucleus and Superior Colliculus
Authors: Novak Nino , Bolz Jürgen
Published: April 2006

Cells in the cerebral cortex project to many distant regions in the brain. Each cortical target receives input from a specific population of cells which have a characteristic morphology and which are located in a distinct cortical layer. In an attempt to learn about the mechanisms by which this stereotypic output pattern is generated during development, we have studied the formation of cortical projections in an in vitro system. Slices from developing rat visual cortex were cocultured with slices from the superior colliculus, the major target of cells in layer 5, and the lateral geniculate nucleus, the major target of cells in layer 6. Cortical neurons which established connections with tectal and thalamic explants were retrogradely labelled with fluorescent dyes. It was found that, in vitro, different populations of neurons project to these two targets, and that the laminar position and cellular morphology of the projecting cells were similar to their in vivo counterparts. These specific connections were established when the target explants were placed either next to the white matter or next to the pial side of cortical slice cultures. The axons of cells projecting to ectopic positioned explants reoriented their trajectories and grew through the cortical grey matter directly towards their targets. Thus subcortical targets exert an orienting effect specifically on their innervating cells and attract growing axons of the appropriate cells at a distance. These results suggest that different targets release different molecules that act selectively on specific populations of neurons. Therefore, chemotropic guidance is likely to play a significant role in the development of specific connections between cortical neurons and their target areas.
Injury‐induced Regulation of Ciliary Neurotrophic Factor mRNA in the Adult Rat Brain
Authors: Ip Nancy Y. , Wiegand Stanley J. , Morse Joanne , Rudge John S.
Published: April 2006

Ciliary neurotrophic factor (CNTF) is a pleiotropic molecule that acts as a neurotrophic factor for a wide range of embryonic neurons as well as a differentiation factor for sympathetic neuroblasts and O2A progenitor cells in culture. CNTF messenger RNA (mRNA) is present at very low levels in the normal adult rat central nervous system (CNS), but is dramatically up‐regulated after an aspiration lesion of dorsal hippocampus and overlying cortex, in the area coincident with glial scar. The increased level of CNTF mRNA in lesioned hippocampus is maximal by 3 days and is sustained for up to 20 days, the longest time point examined. In contrast, mRNA levels for brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3) were slightly decreased during the same period. In situ hybridization experiments revealed that cells expressing CNTF mRNA were concentrated at the margin of the wound, and also present within the gelfoam which filled the lesion cavity. This distribution of CNTF‐expressing cells corresponded very closely to that of cells expressing high levels of glial fibrillary acidic protein mRNA at the wound site. Paralleling the observed increase in CNTF mRNA, increased levels of CNTF‐like neurotrophic activity were apparent in soluble extracts of the lesioned tissues. This neurotrophic activity for ciliary ganglion neurons was completely blocked by the addition of neutralizing antiserum against CNTF. Basic fibroblast growth factor, which has been shown by others to increase after a similar lesion paradigm (Frautschy et al., Brain Res., 553, 291–299, 1991), does not contribute appreciably to this trophic activity. We conclude that CNTF is markedly increased as a function of injury to the CNS and that its expression is most likely restricted to reactive astrocytes in the glial scar.
The L2/HNK‐1 Carbohydrate Mediates Adhesion of Neural Cells to Laminin
Authors: Hall Heike , Liu Li , Schachner Melitta , Schmitz Brigitte
Published: April 2006

The L2/HNK‐1 carbohydrate epitope shared by several neural adhesion molecules has been implicated in cell‐to‐cell and cell‐to‐laminin adhesion (Keilhauer et al., Nature, 316, 728–730, 1985; Künemund et al., J. Cell Biol., 106, 213–223, 1988). As demonstrated previously for chicken retinal ganglion cells (Cole et al., Neurosci. Lett., 93, 170–175, 1988), cerebral cortex astrocytes or cerebellar neurons could not be shown to adhere to the substrate‐bound L2/HNK‐1 carbohydrate. The cell‐bound L2/HNK‐1 carbohydrate, however, was a potent mediator of astrocytic and neuronal cell adhesion to laminin, which was strongly reduced in the presence of the L2/HNK‐1 carbohydrate‐carrying glycolipids or Fab fragments of a monoclonal antibody against it. Inhibition of adhesion could not be observed in the presence of the negatively charged gangliosides or sulphatide, but in the presence of heparin. To investigate whether the L2/HNK‐1 carbohydrate and heparin use the same or different binding sites on laminin, adhesion of cells to laminin was determined in the presence of heparin and Fab fragments of a monoclonal L2 antibody, which gave an additive value of inhibition as compared to the inhibition caused by the single compounds. This result, as well as studies of the binding of the L2/HNK‐1 glycolipids to laminin in the presence of heparin, indicates that the L2/HNK‐1 carbohydrate and heparin are implicated in different aspects of neural cell adhesion to laminin.
Optical Recording of Neuronal Activity in the Insect Central Nervous System: Odorant Coding by the Antennal Lobes of Honeybees
Authors: Lieke Edmund E.
Published: April 2006

Voltage‐sensitive dyes and activity‐dependent intrinsic optical signals were used to study the spatio‐temporal activity in the antennal lobes of honeybees. The intrinsic signals are somewhat slower than the dye signals but show a 10‐fold larger intensity change. These intrinsic signals consist of at least two components—one is wavelength‐independent and the other strongly wavelength‐dependent, with a maximum at ∼500 nm. Local inhibitory connections within the antennal lobes were examined by recording the activity elicited by an electrical stimulus to the antennal nerve of a slice preparation before and after applying picrotoxin to manipulate GABAergic inhibitory synapses. The inhibition starts with a delay of ∼10 ms after onset of the response and has at least two components. The spatial distribution of the inhibition is extremely inhomogeneous, with areas of small inhibition adjacent to areas of large inhibition. Thus inhibitory interactions in the antennal lobes are not evenly distributed among the glomerular organization. Stimulation of an in vivo preparation with an odour yields a spatially restricted activity. However, the spatial map appears highly dynamic in time because the size of the activated area is a function of the time during and after the stimulus.
Currents Activated by GABA and their Modulation by Zn2+ in Cerebellar Granule Cells in Culture
Authors: Kilic Gordan , Moran Oscar , Cherubini Enrico
Published: April 2006

Whole‐cell and single‐channel currents evoked by γ‐aminobutyric acid (GABA) were recorded from rat cerebellar granule cells in culture. The electro‐physiological properties of these currents were studied in control condition and in the presence of external Zn2+ (10 – 30μM). GABA (10 μM) induced bicuculline‐sensitive whole‐cell currents which desensitized. The desensitization was more rapid for higher concentrations of GABA (30 – 300 μM). The current – voltage relation of GABA currents was linear from – 70 to +50 mV. Two different types of cells were found with respect to the stoichiometry for agonist binding, one with Hill coefficient 1.5 and another one with coefficient 1. The half‐maximum concentration displayed more variability, with values varying from 10 to 50 μM. The time constant of recovery from desensitization (Tr) was estimated to be 36 s. Zn2+ (30 μM) blocked GABA‐activated whole‐cell currents in a non‐competitive and voltage‐independent way without a significant change in the current kinetics. In excised outside‐out patches, GABA (0.5 μM) activated single‐channel events of 19 and 31 pS. Kinetic analysis yielded two mean shut times (Tc1= 2.70 ms, Tc2= 205 ms) and one mean open time (To= 3.64 ms). Zn2+ (10 μM) did not affect single‐channel conductances and mean open and shut times, but significantly reduced the probability of opening from 0.17 to 0.06. It is probable that Zn2+ binds to a site located on the extracellular part of the GABAA receptor channel complex.
Regeneration of Hypoglossal Nerve Axons Following Blockade of the Axotomy‐induced Microglial Cell Reaction in the Rat
Authors: Svensson M. , Aldskogius H.
Published: April 2006

The aim of the present study was to examine whether inhibition of the microglial cell reaction around axotomized motoneurons affects the subsequent regeneration process of the injured axons. The microglial cell reaction in the hypoglossal nucleus of the rat was blocked by infusion of cytosine‐arabinoside (ARA‐C) into the ventricular system. Axon regeneration was evaluated by determining the number and size distribution of myelinated axons at a defined level distal to the crush site, the number of neurons which could be retrogradely labelled from the distal stump as well as the number of motor endplates in the tongue at various times following injury. No significant difference was observed for any of these parameters between ARA‐C‐treated and untreated animals. Therefore, it is concluded that the microglial cell reaction is not necessary for peripheral nerves to regenerate and restore target contact at a normal rate and to a normal extent.
Cellular Localization of Interleukin 6 mRNA and Interleukin 6 Receptor mRNA in Rat Brain
Authors: Schöbitz Bernd , de Kloet E. Ronald , Sutanto Win , Holsboer Florian
Published: April 2006

The distribution of interleukin 6 (IL‐6) mRNA and IL‐6 receptor (IL‐6R) mRNA in the brain of adult male rats was studied at the light microscope level by in situ hybridization histochemistry using 35S‐labelled oligonucleotides. The transcripts of both genes were localized in the pyramidal neurons and in the granular neurons of the hippocampus, in neurons of the habenular nucleus as well as in the dorsomedial and ventromedial hypothalamus, in the piriform cortex, in scattered neurons of the cortex and in granular cells of the cerebellum. The medial preoptic nucleus and the anterior tip of the lateral ventricle contained mRNA encoding IL‐6 and its receptor. Moreover, white matter areas, such as the internal capsule, which consist of only fibres and glial cells, were found to have autoradiographic signals above background. The mRNAs for IL‐6 and IL‐6R in hippocampus and cerebellum are not different, as shown by Northern blot analyses of RNA isolated from these tissues. We postulate that the cytokine IL‐6 is expressed constitutively in discrete regions of the CNS and that it is involved in the mechanisms coordinating metabolic, behavioural and neuroendocrine changes not only during illness but also under normal physiological conditions. Our results suggest that IL‐6 mRNA and IL‐6R mRNA are colocalized, thus supporting a role of the cytokine in autocrine and paracrine communication.
Endogenous Histamine in Cultured Bovine Adrenal Chromaffin Cells
Authors: Tuominen Raimo K. , Karhunen Tuula , Panula Pertti , Yamatodani Atsushi
Published: April 2006

Histamine releases catecholamines and opioids in primary cultured bovine adrenal medullary (BAM) chromaffin cells. We have studied whether histamine is synthesized and localized in BAM cells, and whether it can be released upon activation with secretagogues. In BAM cells histamine is immunohistochemically co‐localized with tyrosine hydroxylase in 45 ± 8% of all cells. Only histamine immunoreactivity was observed in 8 ± 2% of all BAM cells. No mast‐cell‐like cells were observed in our system. Histamine can be released from BAM cells by high potassium (56 mM K+) in a calcium‐dependent manner. Compound 48/80 did not release histamine from BAM cells but nicotine caused a dose‐dependent liberation of the amine. Cultured BAM cells have histidine decarboxylase activity which is inhibited by α‐fluoromethylhistidine. These results indicate that endogenous histamine is synthesized, stored and released in BAM chromaffin cells in vitro.
Regional Distribution of Amyloid β‐Protein Precursor, Growth‐associated Phosphoprotein‐43 and Microtubule‐associated Protein 2 Messenger RNAs in the Nigrostriatal System of Normal and Weaver Mutant Mice and Effects of Ventral Mesencephalic Grafts
Authors: Solà C. , Mengod G. , Low W. C. , Norton J. , Ghetti B. , Palacios J. M. , Triarhou L. C.
Published: April 2006

Using in situ hybridization histochemistry with [32P]oligonucleotide probes, we studied the cellular localization of RNA transcripts for amyloid β‐protein precursor (βAPP), growth‐associated phosphoprotein‐43 (GAP‐43) and microtubule‐associated protein 2 (MAP2) in the mesostriatal system of normal (+/+) and weaver (wv/wv) mutant mice, which lose mesencephalic dopamine neurons. In addition, expression of the same messages was studied in ventral mesencephalic cell suspensions transplanted to the weaver striatum. Transcripts encoding GAP‐43, MAP2 and isoforms βAPP695, βAPP714 and βAPP751 were present in normal substantia nigra and progressively reduced in weaver substantia nigra; such a reduction was correlated with dopamine neuron loss. The survival of dopamine neurons in unilateral intrastriatal grafts was documented by methamphetamine‐induced rotational asymmetry tests and by tyrosine hydroxylase immunocytochemistry. High hybridization signals were obtained for GAP‐43, MAP2, βAPP695, βAPP714 and βAPP751 RNA transcripts in the grafted tissue; the βAPP770 species‐normally seen in striatum and not substantia nigra‐was not expressed in the grafts, but it was present in the recipient striatum. Following immunocytochemical labelling with antibodies, GAP‐43 and MAP2 immunoreactivities were seen in cell processes in the grafts and surrounding tissue, whereas βAPP immunoreactivity was mainly found in grafted cell bodies. These results suggest that the transplanted mesencephalic cells mature very similarly to those in the normal substantia nigra, expressing different mRNAs that are normally present in the ventral midbrain and which are reduced in the weaver mutant as a consequence of dopamine neuron loss.
Temporal Integration in Visual Cortex of Cats with Surgically Induced Strabismus
Authors: Eschweiler G. W. , Rauschecker J. P.
Published: April 2006

Single unit response latencies in striate cortex after visual stimulation with stationary flashed bars were measured and interocularly compared in anaesthetized cats with surgically induced strabismus, in order to elucidate the neural basis of strabismic amblyopia. Four unilateral esotropic and two exotropic cats were studied. The visual onset latencies of cortical neurons ranged from 30 to 170 ms after stimulation of the non‐deviating eye at a contrast of 82%. Responses after visual stimulation of the deviating eye were consistently delayed by ∼10 ms. The latency increase was independent of the direction and absolute angle of squint in the different animals. Peak latencies of cortical neurons ranged from 43 to 245 ms. Median peak latency was 85 ms for the non‐deviating and 95 ms for the deviating eye. The rise time of cortical flash responses, as determined from onset ‐ peak differences, ranged between 2 and 170 ms. Direct interocular comparison of response latencies in the remaining binocular neurons revealed an invariable advantage for the non‐deviating eye. Supragranular neurons showed a greater interocular latency difference than neurons in layer IV. Visual latencies were contrast‐dependent. However, the latency reduction with increasing contrast was less pronounced for the deviating eye. We discuss the possibility that central integration times, especially within cortex, are prolonged in strabismic cats, affecting temporal coincidence of signal processing in the visual cortex. The resulting disturbance of spatio‐temporal integration, as caused by a scrambling of geniculo‐striate and intracortical connections, may be the substrate of binocular suppression and strabismic amblyopia.
Large Calibre Primary Afferent Neurons Projecting to the Gracile Nucleus Express Neuropeptide Y after Sciatic Nerve Lesions: an Immunohistochemical and In Situ Hybridization Study in Rats
Authors: Zhang Xu , Meister Björn , Elde Robert , Verge Valerie M.K. , Hökfelt Tomas
Published: April 2006

Using immunohistochemistry and in situ hybridization, we studied changes in expression of some neuropeptides in large and medium‐sized neurons in lumbar 4 and 5 rat dorsal root ganglia projecting to the gracile nucleus, in response to peripheral axotomy. Fourteen days after unilateral sciatic nerve transection, many large neurons and some medium‐sized neurons in ipsilateral dorsal root ganglia were strongly neuropeptide Y‐positive. Galanin‐, vasoactive intestinal polypeptide (VIP)‐ and peptide histidine‐isoleucine (PHI)‐like immunoreactivities coexisted with neuropeptide Y‐like immunoreactivity in some of these neurons. After axotomy numerous large and medium‐sized cells contained neuropeptide Y mRNA in the ipsilateral ganglia, whereas no hybridization was seen in the contralateral or control ganglia. Cross‐sectioned, large neuropeptide Y‐positive fibres were observed in a somatotopically appropriate zone within the ipsilateral gracile fasciculus. A dense network of neuropeptide Y‐immunoreactive, large nerve fibres and terminals was seen in the ipsilateral gracile nucleus. A small number of galanin‐ and VIP/PHI‐like immunoreactive nerve fibres and terminals were also observed in adjacent sections. Neuropeptide Y‐like immunoreactivity colocalized with galanin‐ or VIP/PHI‐like immunoreactivity in some nerve fibres. None of these neuropeptide immunoreactivities could be detected in nerve fibres and terminals in the control or contralateral gracile nucleus. These findings suggest that neuropeptides, in addition to their role in small dorsal root ganglion neurons, may have a function in large and medium‐sized dorsal root ganglion neurons projecting to laminae III and IV in the dorsal horn as well as to the gracile nuclei, as a part of their response to peripheral axotomy.
Neurophysiological Evidence for Increased Kappa Opioidergic Control of Spinal Cord Neurons in Rats with Unilateral Inflammation at the Ankle
Authors: Stiller R. U. , Grubb B. D. , Schaible H.‐G.
Published: April 2006

The role of the endogenous kappa opioid system in the control of neuronal activity has been studied in the spinal cord of normal rats and in rats with Freund's adjuvant induced unilateral inflammation of the ankle under barbiturate anaesthesia. During recordings from neurons with ankle input the kappa receptor agonist U50,488H and/or the kappa antagonist nor‐binaltorphamine were administered ionophoreticaliy using multibarrel electrodes. In most neurons tested U50, 488H reduced the responses evoked by pressure applied across the ankle whereas smaller proportions of neurons showed increased activity or were not affected. The kappa opioid antagonist nor‐binaltorphamine affected more neurons in rats with inflammation than in control rats. Ongoing activity was increased in 7 of 19 (37%) neurons in control rats, in 16 of 24 (67%) neurons in the acute phase of inflammation (2 days post inoculation) and in 15 of 23 (65%) neurons in the chronic phase of inflammation (16–20 days post inoculation). During application of nor‐binaltorphamine in control rats, the responses to pressure were increased in 9 cells (36%), reduced in 7 cells (28%) and unaffected in 9 cells (36%). In the acute phase of inflammation significantly more neurons (11 of 15, 73%) showed enhanced responses to pressure during ionophoresis of nor‐binaltorphamine but not in the chronic phase. These results show that spinal cord neurons with ankle input are influenced by the endogenous kappa opioid system particularly under inflammatory conditions. The upregulation of this system under inflammatory conditions may serve to counteract inflammation‐induced hyperexcitability.
Electrical Kindling of the Hippocampus is Associated with Functional Activation of Neuropeptide Y‐containing Neurons
Authors: Rizzi M. , Monno A. , Samanin R. , Sperk G. , Vezzani A.
Published: April 2006

The release of neuropeptide Y (NPY) was measured from hippocampal slices of rats at stage 2 (preconvulsive stage) and stage 5 (full seizure expression) of electrical kindling of the dorsal hippocampus (upper blade of the dentate gyrus). Spontaneous release in naive rats (9.0 ± 0.8 fmol/ml every 10 min) was independent of external Ca2+ but was reduced by 38 ± 3.6% (P < 0.05) during 20 min incubation with 5μM tetrodotoxin. Spontaneous efflux in naive rats did not differ from that in shams (implanted with electrodes but not stimulated) or in rats kindled to stage 2 and stage 5. Twenty‐five, 50 and 100 mM KCl induced a concentration‐dependent release of NPY (P < 0.05 and P < 0.01 at 25 and 50–100 mM respectively) from slices of shams. The effect of 100 mM KCl was reduced by 94 ± 1% (P < 0.01) in the absence of Ca2+. Two days after the last stage 2 stimulation and 1 week after the last stage 5 seizure, NPY release was significantly larger than in shams at all KCl concentrations in the stimulated and contralateral hippocampus (P < 0.05 and P < 0.01). Forty‐eight hours after one single after‐discharge and 1 month after the last stage 5 seizure, 50 mM KCl induced a significantly larger release of NPY in the stimulated and contralateral hippocampus (P < 0.01 and P < 0.05), although the effect was less than during kindling. The tissue concentration of NPY increased significantly in both hippocampi at stage 2 and 1 week after stage 5 (2.6 times on average, P < 0.01) but no significant differences were found 1 month after stage 5. The present results provide the first evidence of enhanced neuronal release of NPY during kindling, suggesting that this neuropeptide may have a potential role in epileptogenesis.
Intracellular Chloride Activity and the Effect of 5‐Hydroxytryptamine on the Chloride Conductance of Leech Retzius Neurons
Authors: Munsch T. , Schlue W.‐R.
Published: April 2006

Intracellular Cl‐ activity (aCli) and 5‐hydroxytryptamine (5‐HT)‐induced membrane currents of Retzius neurons in the central nervous system of the medicinal leech were measured using Cl‐ sensitive microelectrodes and a two‐microelectrode voltage‐clamp technique. At the membrane of Retzius neurons Cl‐ ions were not passively distributed. Under different conditions the chloride equilibrium potential (ECl, ‐60.1 mV for isotonic saline and ‐57.8 mV for a hypertonic saline) was negative with respect to the membrane potential (Em‐55 ± 3.8 and ‐47 ± 3.4 mV respectively). The endogenous neurohormone 5‐HT always polarized the membrane of Retzius neurons in the direction of ECl. When voltage‐clamping the membrane of Retzius neurons near the resting potential both in situ and in primary culture, application of 5‐HT produced an outward current (l5‐HT) and increase in membrane conductance. Current ‐ voltage relationships for l5‐HTshowed a slight outward rectification and reversal potentials of ‐61.6± 3.1 mV in situ and ‐66± 3.1 mV in primary culture, both values being comparable to the Ecl of Retzius neurons as measured in situ. The results indicate that 5‐HT increases the Cl‐ conductance of Retzius neurons, thereby hyperpolarizing the cell membrane and affecting both the excitability of the neuron and 5‐HT release from it. This could affect the feeding and swimming behaviour of the leech.
Distribution of Secretoneurin‐like Immunoreactivity in Comparison with Substance P‐ and Enkephalin‐like Immunoreactivities in Various Human Forebrain Regions
Authors: Marksteiner J. , Saria A. , Kirchmair R. , Pycha R. , Benesch H. , Fischer‐Colbrie R. , Haring C. , Maier H. , Ransmayr G.
Published: April 2006

The distribution of secretoneurin‐like immunoreactivity, a peptide derived from secretogranin II, was studied by means of immunocytochemistry and compared to the pattern of staining for substance P‐ and enkephalin‐like immunoreactivities in the human basal forebrain, with special reference to the basal ganglia. Secretoneurin‐like immunoreactivity was characterized by gel filtration and reversed‐phase high pressure liquid chromatography analysis. Chromatographic analysis revealed a single peak for secretoneurin‐like immunoreactivity. No secretoneurin‐immunopositive forms of high molecular weight were found. Secretoneurin‐like immunoreactivity appeared mainly in dot‐ and fibre‐like structures. In addition, a band‐like terminal staining (woolly fibres) that has been shown by others for substance P‐ and enkephalin‐like immunoreactivities, was also observed for secretoneurin‐like immunoreactivity. Medium‐sized cells were found arranged in clusters or singly within the caudate and putamen. In the basal ganglia, a high density of secretoneurin‐like immunoreactivity was found in the internal segment of the globus pallidus, the ventral pallidum and in the pars reticulata of the substantia nigra. In these areas the immunostaining appeared mainly as woolly fibres. The bed nucleus of the stria terminalis and medial amygdala displayed a high density of fine beaded secretoneurin‐like immunoreactive fibres, sometimes forming pericellular contacts. The nucleus basalis of Meynert was highly innervated by secretoneurin‐like immunoreactive fibres, mainly in the form of woolly fibres. In general, a large overlap was found between secretoneurin‐ and substance P‐like immunoreactivity in all examined areas of the basal ganglia. In the bed nucleus of the stria terminalis and medial amygdala secretoneurin‐like immunoreactivity was distributed very similarly to enkephalin‐like immunoreactivity. These data provide evidence that in different subsets of neurons and neuronal pathways secretoneurin‐like immunoreactivity coexists with substance P‐ and enkephalin‐like immunoreactivity in several areas of the human brain.
Rapid Decline in the Ability of Entorhinal Axons to Innervate the Dentate Gyrus With Increasing Time in Organotypic Co‐culture
Authors: Woodhams Peter L. , Atkinson D. John , Raisman Geoffrey
Published: April 2006

We have used the species‐specific monoclonal antibodies OM1 and OM4 to identify the histiotypic pattern of projection from late embryonic rat entorhinal explants to the outer molecular layer of the dentate gyrus in organotypic cultures of 6‐day postnatal mouse hippocampal slices. The presence of this entorhinal projection was detectable with the rat‐specific OM1 and OM4 markers after 3–7 days in co‐culture, and confirmed by use of the later‐forming rat neuron‐specific marker Thy‐1.1, which appeared during the second week. Hippocampal slices confronted with control explants of superior colliculus for 4 weeks in culture showed only sparse, non‐specific growth of axons with no histiotypic pattern in the dentate gyrus. In order to assess whether the formation of specific entorhino‐dentate projections in vitro is age‐dependent, embryonic rat entorhinal cortical explants were cultured alone for periods of 1 ‐ 5 weeks before cutting across the halo of axons radiating into the collagen matrix and presenting each with 6‐day‐old mouse hippocampal slices as targets to innervate. After allowing a 2 week period for fibre growth to take place, the density of immunostained axonal outgrowth was scored on a five‐point scale for each weekly interval. The amount of new axon growth when the cuts were made after 1 week was slightly reduced compared to undamaged control cultures. However, outgrowth was greatly diminished when the cuts were made after 2 or 3 weeks, and essentially abolished if the interval was extended to ≥4 weeks. Thus we demonstrate that, although hippocampal slices can survive in organotypic co‐culture with entorhinal explants and maintain previously formed connections, the explants show an age‐related failure in the ability to form new connections. Such a system provides a possible in vitro model for study of the factors influencing the failure of regeneration in the adult central nervous system.
Survival‐promoting and Protein Kinase C‐regulating Roles of Basic FGF for Hippocampal Neurons Exposed to Phorbol Ester, Glutamate and Ischaemia‐like Conditions
Authors: Louis Jean‐Claude , Magal Ella , Gerdes Wilhelm , Seifert Wilfried
Published: April 2006

Recent evidence suggests that protein kinase C (PKC) is involved in the pathophysiology of neurodegenerative diseases. We examined the effect of basic fibroblast growth factor (bFGF) on the survival of cultured rat hippocampal neurons exposed to conditions in which PKC is likely to play a role. bFGF reduced neuron damage caused by the PKC‐activating phorbol ester 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), glutamate and ischaemia‐like culture conditions. bFGF was able to counteract the excessive activation of PKC caused by these treatments. Moreover, bFGF prevented the loss of PKC occurring after prolonged exposure to TPA or ischaemia‐like conditions. These results indicate that both the overactivation and the abnormal degradation of PKC can lead to neuron degeneration, and that the neurotrophic competence of bFGF may reside in its ability to regulate and normalize the PKC phosphorylating system.