bluuebunny/crossref_metadata_2025 huggingface dataset:
c‐Jun expression after axotomy of corneal trigeminal ganglion neurons is dependent on the site of injury
Authors: De Felipe Carmen , Belmonte Carlos
Published: March 2003

The proto‐oncogene c‐Jun has been implicated in the control of neuronal responses to injury and in axonal growth during regenerative processes. We have investigated the expression of c‐Jun during normal terminal remodelling in trigeminal ganglion neurons innervating the cornea and after acute injury of epithelial nerve terminals or parent axons. Remodelling and rearrangement, or damage limited to corneal epithelium endings, was not a trigger for activation of c‐Jun expression. However, injury of parent axons in the stroma or in the orbital ciliary nerves induced c‐Jun expression in 50% of the population of corneal neurons, which included all of the large myelinated and 20% of the small neuropeptide‐containing corneal neurons. This suggests that c‐Jun expression in trigeminal ganglion neurons is not associated with normal remodelling or regeneration of peripheral nerve terminals, and that it takes place only when parent axons are injured. A substantial number of damaged neurons do not express c‐Jun, indicating that in primary sensory neurons, injury and regeneration may not always be coupled to the expression of this proto‐oncogene.
Neuropeptide Y increases intracellular calcium in rat pinealocytes
Authors: Simonneaux Valérie , Rodeau Jean‐Luc , Calgari Christiane , Pévet Paul
Published: March 2003

Abstract

The pineal gland is mainly innervated by sympathetic fibres containing noradrenaline (NA) and neuropeptide Y (NPY). NA released at night stimulates melatonin synthesis via a β1‐adrenergic‐induced increase in cyclic adenosine monophosphate (cAMP) concentration potentiated by an α1‐adrenergic‐induced increase in Ca2+ concentration. We previously showed that NPY acted on presynaptic Y2 receptors inhibiting NA release and on postsynaptic Y1 receptors stimulating melatonin synthesis. Here we used Fura‐2 imaging to assess the effect of NPY on the intracellular Ca2+ concentration, [Ca2+]i, in cultured rat pineal cells. In 84% of cells, on average, 10 nm NPY induced a progressive rise of [Ca2+]i from its basal value of 102 ± 3 nm to a plateau of 180 ± 6 nm (n = 467 cells), which lasted the time of NPY application. This effect of NPY appeared dependent on extracellular Ca2+.
Suppression of epileptogenesis by modification of N‐methyl‐d‐aspartate receptor subunit composition
Authors: Bengzon Johan , Okabe Shigeo , Lindvall Olle , McKay Ronald D. G.
Published: March 2003

The effects of altered N‐methyl‐d‐aspartate (NMDA) receptor subunit composition on seizure development in kindling epilepsy were assessed in transgenic mice expressing high neuronal levels of NR2D under control of the calcium/calmodulin kinase II alpha subunit (αCaMKII) promoter. The NR2D subunit is normally present at very low levels in the mature forebrain. Transgenic mice showed a marked reduction of amygdala kindling development. Spread of epileptic activity was retarded and generalized seizures appeared later in animals overexpressing NR2D compared with wild‐type mice. The progressive lengthening of epileptiform activity, which normally occurs in kindling, was also dampened in transgenic animals. We conclude that NMDA receptor subunit composition determines the progression of experimental epilepsy.
Spatiotemporal patterning of glutamate receptors in developing ferret striate cortex
Authors: Smith Adam L. , Thompson Ian D.
Published: March 2003

We have studied glutamate receptor levels during very early phases of cortical formation by using quantitative in vitro autoradiography to map the expression of NMDA, AMPA and kainate receptors in the developing primary visual cortex of the ferret. NMDA and non‐NMDA receptors exhibit very different developmental profiles in primary visual cortex. NMDA receptor density is low at birth and increases throughout the first 2 postnatal months, rising between threefold (layers II/III) and ninefold (layer VI). In contrast, AMPA receptors are abundant at birth and their density remains constant for the first postnatal month, before rising by a maximum of 1.7‐fold (layer I) at around the time of eye‐opening (postnatal day 32). Kainate receptors are also present in high levels at birth and their expression levels rise in the early postnatal period by between 1.5‐fold (layer I) and threefold (layers V/VI) to a peak just after eye‐opening. The proportion of the total ionotropic glutamate receptor binding contributed by NMDA receptors thus rises from 5% at birth to a maximum of 22% at 2 months of age, while the AMPA receptor contribution falls from 87% to 72% over the same period. Below cortex, all three glutamate receptor subtypes are expressed in the subplate region for the first 3 postnatal weeks. These developmental patterns, combined with the fact that AMPA receptors are densely expressed in the proliferative zones underlying presumptive area 17, indicate that non‐NMDA receptor expression levels in primary visual cortex are mostly specified much earlier than those of NMDA receptors.
Ontogeny of water transport in rat brain: postnatal expression of the aquaporin‐4 water channel
Authors: Wen H. , Nagelhus E. A. , Amiry‐Moghaddam M. , Agre P. , Ottersen O. P. , Nielsen S.
Published: March 2003

Brain water transport is poorly understood at the molecular level, and marked changes occur during brain development. As the aquaporin‐4 (AQP4) water channel protein is abundant in brain, the expression levels and subcellular distribution of this protein were examined during postnatal development. This study focused on the cerebellum, which showed the same pattern of AQP4 development as the rest of the brain. Semiquantitative immunoblotting revealed very low levels of AQP4 in the first postnatal week. A pronounced increase was noted in the second week, from 2% of adult level at postnatal day 7 (PN7) to 25% at PN14. At PN1 and PN3 immunofluorescence microscopy revealed weak labelling, mainly in radial processes (Bergmann fibres) and at the pial surface. Between PN7 and PN14 the labelling underneath the pia showed a strong increase, and immunoreactivity also appeared around blood vessels throughout the cerebellum. High‐resolution immunogold electron microscopy revealed that the subpial and perivascular labelling was restricted to glial end feet, notably to those plasma membrane domains that were apposed to the basal laminae. At no stage was there any evidence of neuronal AQP4 labelling, and AQP1, −2, −3 and −5 proteins were not detected in the neuropil. Riboprobes to AQP4 mRNA produced a particularly strong in situ hybridization signal in glial cells between PN7 and PN14, corresponding to the stage of the most rapid increase of AQP4 protein. The time course and pattern of AQP4 expression suggests that this aquaporin plays an important role in brain water and K+ homeostasis from the second week of development.
Immunocytochemical localization of the vanilloid receptor 1 (VR1): relationship to neuropeptides, the P2X3 purinoceptor and IB4 binding sites
Authors: Guo A. , Vulchanova L. , Wang J. , Li X. , Elde R.
Published: March 2003

The vanilloid receptor (VR1) protein functions both as a receptor for capsaicin and a transducer of noxious thermal stimuli. To determine the expression and targetting of this protein, we have generated antisera against both the amino and carboxy termini of VR1. Within the dorsal root and trigeminal ganglia of rats, VR1‐immunoreactivity (VR1‐ir) was restricted to small and medium sized neurons. VR1‐ir was transported into both the central and peripheral processes of these primary afferent neurons, as evidenced by: (i) the presence of VR1‐ir in nerve fibres and terminals in lamina I and lamina II of the superficial dorsal horn, and the association of VR1‐ir with small diameter nerve fibres in the skin and cornea; (ii) the reduction of VR1‐ir in the spinal cord after dorsal rhizotomy; and (iii) the accumulation of VR1‐ir proximal to sciatic nerve ligation. At the ultrastructural level, VR1‐ir was associated with plasma membranes of neuronal perikarya in dorsal root ganglia and nerve terminals in the dorsal horn. VR1‐ir was also seen in nerve fibres and terminals in the spinal trigeminal nucleus and nucleus of the solitary tract. Within a large proportion of dorsal root ganglion neurons and the terminals of their axons, VR1‐ir was colocalized with staining for the P2X3 purinoceptor, and with binding sites for the lectin IB4. Surprisingly, VR1‐ir did not coexist substantially in nerve fibres and terminals that contain substance P and calcitonin gene‐related peptide, suggesting complex mechanisms for the release of these neuropeptides in response to capsaicin application.
Expression of Ras‐GRF in the SK‐N‐BE neuroblastoma accelerates retinoic‐acid‐induced neuronal differentiation and increases the functional expression of the IRK1 potassium channel
Authors: Tonini Raffaella , Mancinelli Enzo , Balestrini Monica , Mazzanti Michele , Martegani Enzo , Ferroni Arnaldo , Sturani Emmapaola , Zippel Renata
Published: March 2003

Ras‐GRF, a neuron‐specific Ras exchange factor of the central nervous system, was transfected in the SK‐N‐BE neuroblastoma cell line and stable clones were obtained. When exposed to retinoic acid, these clones showed a remarkable enhancement of Ras‐GRF expression with a concomitant high increase in the level of active (GTP‐bound) Ras already after 24 h of treatment. In the presence of retinoic acid, the transfected cells stopped growing and acquired a differentiated neuronal‐like phenotype more rapidly than the parental ones. Cells expressing Ras‐GRF also exhibited a more hyperpolarized membrane potential. Moreover, treatment with retinoic acid led to the appearance of an inward rectifying potassium channel with electrophysiological properties similar to IRK1. This current was present in a large number of cells expressing Ras‐GRF, while only a small percentage of parental cells exhibited this current. However, Northern analysis with a murine cDNA probe indicated that IRK1 mRNA was induced by retinoic acid at a similar level in both kinds of cells. Brief treatment with a specific inhibitor of the mitogen‐activated protein kinase (MAPK) pathway reduced the number of transfected cells showing IRK1 activity. These findings suggest that activation of the Ras pathway accelerates neuronal differentiation of this cell line. In addition, our results suggest that Ras‐GRF and/or Ras‐pathway may have a modulatory effect on IRK1 channel activity.
Scorpion α‐like toxins, toxic to both mammals and insects, differentially interact with receptor site 3 on voltage‐gated sodium channels in mammals and insects
Authors: Cestèle Sandrine , Stankiewicz Maria , Mansuelle Pascal , De Waard Michel , Dargent Bénédicte , Gilles Nicolas , Pelhate Marcel , Rochat Hervé , Martin‐Eauclaire Marie‐France , Gordon Dalia
Published: March 2003

α‐Like toxins, a unique group designated among the scorpion α‐toxin class that inhibit sodium channel inactivation, are highly toxic to mice but do not compete for α‐toxin binding to receptor site 3 on rat brain sodium channels. We analysed the sequence of a new α‐like toxin, which was also highly active on insects, and studied its action and binding on both mammalian and insect sodium channels. Action of the α‐like toxin on isolated cockroach axon is similar to that of an α‐toxin, and the radioactive toxin binds with a high affinity to insect sodium channels. Other sodium channel neurotoxins interact competitively or allosterically with the insect α‐like toxin receptor site, similarly to α‐toxins, suggesting that the α‐like toxin receptor site is closely related to receptor site 3. Conversely, on rat brain sodium channels, specific binding of 125I‐α‐like toxin could not be detected, although at high concentration it inhibits sodium current inactivation on rat brain sodium channels. The difficulty in measuring binding to rat brain channels may be attributed to low‐affinity binding due to the acidic properties of the α‐like toxins that also impair the interaction with receptor site 3. The results suggest that α‐like toxins bind to a distinct receptor site on sodium channels that is differentially related to receptor site 3 on mammalian and insect sodium channels.
Blockade of neurotensin receptors suppresses the dopamine D1/D2 synergism on immediate early gene expression in the rat brain
Authors: Alonso R. , Gnanadicom H. , Fréchin N. , Fournier M. , Fur G. Le , Soubrié P.
Published: March 2003

A remarkable feature of dopamine functioning is that the concomitant activation of D1‐like and D2‐like receptors acts to intensify the expression of various dopamine‐dependent effects, in particular the expression of the immediate‐early genes, c‐fos and zif268. Using non‐peptide neurotensin receptor antagonists, including SR48692, we have determined that blockade of neurotensin receptors reduced the cooperative responses of direct acting D2‐like (quinpirole) and partial D1‐like (SKF38393) dopamine agonists on the expression of Fos‐like antigens and zif268 mRNA. Pretreatment with SR48692 (3 and 10 mg/kg) reduced the number of Fos‐like immunoreactive cells produced by the combined administration of SKF38393 (20 mg/kg) and quinpirole (1 mg/kg) in the caudate‐putamen, nucleus accumbens, globus pallidus and ventral pallidum. High‐affinity neurotensin receptors are likely to be involved in these D1‐like/D2‐like cooperative responses, as compounds structurally related to SR48692, SR48527 (3 mg/kg) and its (–)antipode, SR49711 (3 mg/kg), exerted a stereospecific antagonism in all selected brain regions. Pretreatment with SR48692 (10 mg/kg) also diminished Fos induction by the indirect dopamine agonist, cocaine (25 mg/kg), particularly at the rostral level of the caudate‐putamen. In situ hybridization experiments in the caudate‐putamen indicated that SR48692 (10 mg/kg) markedly reduced zif268 mRNA labelling produced by SKF38393 plus quinpirole in cells not expressing enkephalin mRNA, but was unable to affect the concomitant decrease of zif268 mRNA labelling in enkephalin‐positive cells. Taken together, the results of the present study indicate that neurotensin is a key element for the occurrence of cooperative responses of D2‐like and partial D1‐like agonists on immediate‐early gene expression.
X‐ray kinematic analysis of shoulder movements during target reaching and food taking in the cat
Authors: Boczek‐Funcke A. , Kuhtz‐Buschbeck J. P. , Illert M.
Published: March 2003

Co‐ordinate movements around the shoulder are essential during reaching movements. We performed a quantitative kinematic analysis of movements of the shoulder girdle: three‐dimensional X‐ray frames (time resolution 20 ms) were recorded during the target‐reaching and food‐taking paradigm in five cats either sitting (n = 4) or standing (n = 1) in front of a food well. Movements of the scapula consisted of a flexion of the scapula (anteversion of the glenoid) followed by flexion of the gleno‐humeral joint (decrease in the angle between the scapular spine and humerus). In the sitting animals, the gleno‐humeral flexion reversed to extension some 120 ms before object contact, while in the standing animal flexion continued during the ongoing scapular flexion. In both cases, the scapula was nearly horizontal at the end of target reaching. The fulcrum for scapular movements was located near the vertebral border of the scapula at the medial elongation of the scapular spine. No major translational components of the fulcrum with respect to the trunk were found during reaching. Together with full flexion of the scapula, this reduces the number of degrees of freedom considerably and thereby probably simplifying the specification of the end‐point of the limb chain. End‐point specification is further supported by rotational movements of the scapula. In the sitting animal, the amplitude of inward rotation along the long axis of the scapula was around 20 °, while it was much more variable in the standing animal, reflecting more variable starting positions. We hypothesize that the glenoid is used to ‘foveate’ the target object.
Vasopressin released within the septal brain area during swim stress modulates the behavioural stress response in rats
Authors: Ebner Karl , Wotjak Carsten T. , Holsboer Florian , Landgraf Rainer , Engelmann Mario
Published: March 2003

The aim of the present study was to investigate the physiological significance of the neuropeptide arginine vasopressin (AVP) released within the septum, in the behavioural response of rats to stress. In the first experiment, rats were chronically implanted with a microdialysis probe aimed at the mediolateral or ventral septum to monitor the local release of AVP in response to 10 min of forced swimming in 20 °C warm water. Exposure to this stressor caused a significant increase in AVP release in both the mediolateral (174 ± 21%, P < 0.01) and ventral septum (220 ± 33%, P < 0.01). In contrast, microdialysates collected outside the mediolateral septum or in the lateral ventricle remained at prestress levels throughout the dialysis period. Furthermore, unstressed control animals failed to show significant alterations in vasopressin release in the mediolateral septum. In a second experiment, the introduction of the V1 receptor antagonist d(CH2)5Tyr(Me)AVP into the mediolateral septum via inverse microdialysis concomitant with stressor exposure caused the rats to spend an increased time floating and a reduced time swimming compared to vehicle‐treated rats. This effect was acute and also detected 24 h after antagonist administration. Taken together, these findings demonstrate a significant activation of the septal vasopressinergic system in response to swim stress. Furthermore, our data support the view that AVP released within this brain area is involved in the generation of active behavioural strategies aimed at coping with new and challenging situations.
Reaction time performance following unilateral striatal dopamine depletion and lesions of the subthalamic nucleus in the rat
Authors: Phillips Janice M. , Brown Verity J.
Published: March 2003

The akinesia resulting from Parkinson's disease or striatal dopamine depletion in experimental animals can be ameliorated or reversed by inactivation of the subthalamic nucleus. This inactivation might be effective by restoring balance to the basal ganglia motor circuits. Alternatively, new movement‐related deficits might be introduced which mask the original impairments (e.g. hyperkinesia might replace hypokinesia). In the present study, striatal dopamine depletion was effected unilaterally, in order to dissociate generalized effects, e.g. hyperkinesia, from response‐specific initiation effects. Rats were trained in a lateralized visual reaction time task and then assigned to one of four groups: striatal dopamine depletion; cell body lesion of the subthalamic nucleus; combined striatal dopamine depletion and subthalamic nucleus lesion; or control.

As expected, rats with striatal dopamine depletion exhibited slower reaction time and a bias to respond to the ipsilateral side. The subthalamic nucleus lesion resulted in no reaction time change (in particular, there was no evidence of faster reaction times), but there was an increase in anticipatory responding. The group with the combined striatal dopamine depletion and subthalamic nucleus lesion had no reaction time impairment. This group showed an increase in anticipatory errors and a contralateral response bias. These data demonstrate that lesions of the subthalamic nucleus do not merely cancel the akinesia which follows striatal dopamine depletion by the addition of a hyperkinetic impairment. Rather, there appears to be a change in the balance of the motor system.
Acetylcholinesterase and inhibitors: effects upon normal and regenerating nerves of the rat
Authors: Keymer Juan Eduardo , Gaete Jorge , Kameid Gonzalo , Alvarez Jaime
Published: March 2003

In peripheral nerves, the function of acetylcholinesterase (AChE) is not related to hydrolysis of acetylcholine. To test for a trophic role, AChE or its inhibitors were administered locally to normal and regenerating nerves of rats. In the normal nerve, neither AChE nor serum albumin affected the cytological pattern of the nerve. BW284c51, a specific inhibitor of AChE, resulted in demyelination, proliferation of Schwann cells and sprouting of axons after 5–7 days. Edrophonium or propidium, other specific inhibitors of AChE, did so to a much lesser extent. Vehicle, and iso‐OMPA (inhibitor of pseudocholinesterases) did not affect the cytology of the nerve. Elongation of regenerating axons was evaluated at day 3 post‐crush. Native AChE applied distal to the crush reduced the elongation of regenerating axons (– 36%), while serum albumin, heated AChE and filtered AChE did not. BW284c51, edrophonium or propidium enhanced the axonal elongation (33%) when they were administered for 2 days before, but not after, the crush. Iso‐OMPA or vehicle administered before or after the crush were not effective. Thus, AChE reduces elongation of regenerating axons, while inhibition of AChE enhances elongation and affects the cytology of the normal nerve as well. We propose that AChE has a trophic role in mammalian peripheral nerves.
Origins of the glycinergic inputs to the rat locus coeruleus and dorsal raphe nuclei: a study combining retrograde tracing with glycine immunohistochemistry
Authors: Rampon Claire , Peyron Christelle , Gervasoni Damien , Pow David V. , Luppi Pierre‐Hervé , Fort Patrice
Published: March 2003

The amino acid glycine is a major inhibitory neurotransmitter in the brainstem and is likely involved in the tonic inhibition of the monoaminergic neurons during all sleep‐waking stages. In order to determine the neurons at the origin of the glycinergic innervation of the two principal monoaminergic nuclei, the locus coeruleus and the dorsal raphe of the rat, we applied a double‐labelling technique, combining retrograde transport of cholera‐toxin B subunit with glycine immunohistochemistry. Using this technique, we found that the locus coeruleus and dorsal raphe nuclei receive a common glycinergic innervation from the ventral and ventrolateral periaqueductal grey, including the adjacent deep mesencephalic reticular nucleus. Small additional glycinergic inputs to these nuclei originated from the lateral paragigantocellular nucleus and the rostral ventromedial medullary reticular formation. The potential role of these glycinergic inputs in the control of the excitability of the monoaminergic neurons of the locus coeruleus and dorsal raphe nuclei is discussed.
Cytochrome c release and caspase‐3 activation during colchicine‐induced apoptosis of cerebellar granule cells
Authors: Gorman A. M. , Bonfoco E. , Zhivotovsky B. , Orrenius S. , Ceccatelli S.
Published: March 2003

The microtubule‐disrupting agent colchicine is known to be neurotoxic toward certain neuronal populations including cerebellar granule cells (CGCs). In this study we investigated the involvement of cytochrome c release and caspase‐3 activation during colchicine‐induced CGC apoptosis. Treatment of rat CGCs with 1 μm colchicine (for up to 24 h) caused high molecular weight DNA fragmentation and nuclear condensation. An involvement of group II caspases (which includes caspase‐3) was demonstrated by the proteolytic degradation of poly(ADP‐ribose) polymerase (PARP) after 18 h exposure to colchicine. Colchicine induced a time‐dependent increase in Ac‐Asp‐Glu‐Val‐Asp‐α‐(4‐methyl‐coumaryl‐7‐amide) (DEVD‐MCA) cleavage activity in CGCs, which was blocked with a specific, peptide‐based, aldehyde inhibitor of group II caspases, i.e. DEVD‐CHO. We also observed a time‐dependent proteolysis of caspase‐3 as judged by the appearance of p17 which is one of the subunits of active caspase‐3. Activation of caspase‐3 during colchicine‐induced apoptosis may be mediated by cytochrome c since there was a close correlation between the time courses of cytochrome c release from the mitochondria and of caspase‐3 activation. Furthermore, colchicine‐induced apoptosis, as assessed by propidium iodide visualization of the nuclei, could be blocked by the caspase inhibitor benzyloxycarbonyl‐Val‐Ala‐Asp (O‐methyl) fluoromethyl ketone.
GDNF family ligands and receptors are differentially regulated after brain insults in the rat
Authors: Kokaia Zaal , Airaksinen Matti S. , Nanobashvili Avtandil , Larsson Elin , Kujamäki Eila , Lindvall Olle , Saarma Mart
Published: March 2003

Expression of mRNAs for glial cell line‐derived neurotrophic factor (GDNF), neurturin (NTN) and their receptors was studied in adult rat brain using in situ hybridization after 40 kindling‐evoked, rapidly recurring seizures or 10 min of global forebrain ischaemia. Following seizures, GDNF and NTN mRNAs were elevated in dentate granule cells, and c‐Ret mRNA in hilar neurons and non‐pyramidal cells in CA1 and CA3 regions. GFRα‐1 mRNA levels showed more widespread increases in the dentate granule cell layer and hilus, CA1 and CA3 pyramidal layers, basolateral amygdala and parietal cortex. The expression of GFRα‐2 mRNA increased in the piriform cortex and decreased in the CA1 region and basolateral amygdala. Forebrain ischaemia induced elevated expression of GDNF mRNA in dentate granule cells, GFRα‐1 mRNA in the dentate granule cell layer, hilus and CA3 pyramidal layer, and GFRα‐2 mRNA in the parietal cortex. The gene expression patterns observed here suggest that GDNF and NTN may act as target‐derived factors, but also in an autocrine or paracrine manner. GFRα‐1 can be coexpressed with GFRα‐2 and c‐Ret mRNAs in the same hippocampal or thalamic neurons, but other neurons contain GFRα‐1 alone or together with c‐Ret mRNA. The gene expression changes for the ligands, and the receptor components are region‐, cell‐ and insult‐specific, and occur independently of each other, mainly within 24 h after seizures or ischaemia. This dynamic regulation of GDNF and NTN circuits primarily at the receptor level may be important for the effectiveness of neuroprotective responses but could also trigger plastic changes, e.g. those underlying the development of epileptic syndromes.
AMPA‐preferring receptors with high Ca2+ permeability mediate dendritic plasticity of retinal horizontal cells
Authors: Okada Takashi , Schultz Konrad , Geurtz Wiltrud , Hatt Hanns , Weiler Reto
Published: March 2003

The synaptic complex formed by the cone photoreceptor pedicles and the dendrites of horizontal cells in the teleost retina undergoes structural changes during light adaptation. Numerous spinules are formed by the terminal dendrites, and they are subsequently retracted during dark adaptation. In a retina kept under continuous illumination, the retraction process can be initiated by analogues of the neurotransmitter glutamate acting at AMPA/kainate receptors. On the other hand, the retraction process depends on calcium influx and the subsequent activation of CaMkII. We show here that the retraction of spinules induced by AMPA or kainate is not impaired in the presence of cobalt, making an involvement of voltage‐gated calcium channels unlikely. Using calcium imaging techniques with isolated horizontal cells, we demonstrate that AMPA and kainate, but not NMDA, increase [Ca2+]i in the presence of nicardipine, caffeine and thapsigargin. The increase of [Ca2+]i under these conditions depends on [Ca2+]o and on the agonist in a dose‐dependent manner, suggesting that the increase of [Ca2+]i is largely due to calcium influx through the agonist‐gated channel. Pharmacological studies were performed to determine whether AMPA‐ and/or kainate‐preferring receptors mediate the calcium influx. The AMPA‐preferring receptor antagonist LY303070 blocked glutamate‐ and kainate‐evoked increases of [Ca2+]i in a concentration‐dependent manner, indicating that kainate‐preferring receptors contributed little or nothing to the observed [Ca2+]i increase. This was supported by experiments where cyclothiazide (which blocks the desensitization of AMPA receptors) and concanavalin A (which potentiates responses mediated by kainate receptors) were applied. In all cases, LY303070 blocked the agonist‐evoked increase of [Ca2+]i. The presence of AMPA‐preferring receptors with high Ca2+ permeability on horizontal cells was also supported by measuring agonist‐induced currents using whole‐cell recording techniques. Furthermore, LY303070 was able to impair the retraction of spinules during dark adaption in the in vivo situation.
Semaphorin D acts as a repulsive factor for entorhinal and hippocampal neurons
Authors: Steup Andreas , Ninnemann Olaf , Savaskan Nicolai E. , Püschel Robert Nitsch andreas W. , Skutella Thomas
Published: March 2003

We analysed the effects of semaphorin D on axons from the developing rat entorhinal–hippocampal formation. Explants from superficial layers of the entorhinal cortex and of the hippocampus anlage were obtained from various developmental stages and co‐cultured with cell aggregates expressing semaphorin D. Neurites extending from entorhinal explants that had been isolated from early embryonic stages (E16 and E17) were not affected by semaphorin D, but were repelled at later stages (E20 and E21). Axons from hippocampal neurons explanted at E21 were also repelled by semaphorin D. In situ hybridization studies revealed expression of the semaphorin D receptor neuropilin‐1 in the entorhinal cortex from stage E17 to stage P7, and in the dentate gyrus and CA1–3 regions between E17 and adulthood. These data suggest that semaphorin D is involved in the formation of the perforant pathway and acts, via the neuropilin‐1 receptor, as a repulsive signal that prevents entorhinal fibres from growing into the granular layer of the dentate gyrus. These data also suggest a role for semaphorin D in the development of intrahippocampal connections.
Dorsolateral prefrontal cortex: comparative cytoarchitectonic analysis in the human and the macaque brain and corticocortical connection patterns
Authors: Petrides M. , Pandya D. N.
Published: March 2003

The cytoarchitecture of the human and the macaque monkey dorsolateral prefrontal cortex has been examined in a strictly comparative manner in order to resolve major discrepancies between the available segmentations of this cortical region in the human and the monkey brain. In addition, the connections of the dorsolateral prefrontal cortical areas were re‐examined in the monkey. The present analysis showed that only a restricted portion of what had previously been labelled as area 46 in the monkey has the same characteristics as area 46 of the human brain; the remaining part of this monkey region has the characteristics of a portion of the middle frontal gyrus in the human brain that had previously been included as part of area 9. We have labelled this cortical area as 9/46 in both species. These two areas (i.e. 46 and 9/46), which constitute the lower half of the mid‐dorsolateral frontal cortex, have a well‐developed granular layer IV, and can easily be distinguished from area 9, on the upper part of the mid‐dorsolateral region, which does not have a well‐developed granular layer IV. Area 9 has the same basic pattern of connections as areas 46 and 9/46, but, unlike the latter areas, it does not receive input from the lateral parietal cortex. Caudal to area 9, on the dorsomedial portion of the frontal cortex, there is a distinct strip of cortex (area 8B) which, unlike area 9, receives significant input from the prestriate cortex and the medial parietal cortex. The present results provide a basis for a closer integration of findings from functional neuroimaging studies in human subjects with experimental work in the monkey.
GABAB‐receptor‐mediated control of GABAergic inhibition in rat histaminergic neurons in vitro
Authors: Stevens David R. , Kuramasu Atsuo , Haas Helmut L.
Published: March 2003

The onset of slow wave sleep may require an inhibition of histaminergic neurons by GABAergic afferents from the ventrolateral preoptic area. We have utilized electrophysiological methods in an in vitro brain slice preparation to examine the role of GABAB receptor activation in GABAergic synaptic inhibition in histaminergic neurons of the tuberomammillary nucleus. Tetrodotoxin blocked evoked GABAergic IPSPs but not miniature IPSPs or IPSCs. Evoked IPSPs varied in amplitude and exhibited failures of transmission. Baclofen reduced the amplitude of evoked IPSPs in all experiments and often caused an increase in failures of transmission. Responses elicited by application of exogenous GABA were insensitive to baclofen treatment. The action of baclofen was blocked by CGP‐35348 (100 μm), a GABAB receptor antagonist, which also enhanced the amplitude of evoked IPSPs. The frequency of spontaneous and miniature IPSPs and IPSCs was reduced by baclofen. However, the amplitude distribution of mIPSCs was not altered. We conclude that GABA release onto TM neurons is under presynaptic control via GABAB receptors. This presynaptic control of transmission to tuberomammillary neurons may reduce inhibition, increasing histamine release and enhancing wakefulness.
The mechanism of Ara‐C‐induced apoptosis of differentiating cerebellar granule neurons
Authors: Courtney Michael J. , Coffey Eleanor T.
Published: March 2003

Neurotoxicity is one of the side‐effects of the therapeutically useful antitumour agent, Ara‐C (or 1‐beta‐d‐arabinofuranosyl‐cytosine, cytarabine). This agent is also reported to induce cell death of cultured neurons. In this study, we show that Ara‐C‐induced death of differentiating rat cerebellar granule neurons is prevented by cycloheximide at concentrations corresponding to its action in preventing protein synthesis. The death is accompanied by cleavage of the caspase substrate poly ADP ribose polymerase (PARP) and c‐Abl‐dependent activation of the stress‐activated protein kinases c‐Jun N‐terminal kinase and p38. However, c‐Jun levels do not rise and the activation of the stress‐activated protein kinases is not required for this form of neuronal death. Cyclin‐dependent kinase (cdk) activity and inappropriate cell‐cycle re‐entry have been implicated in some forms of death in differentiated neurons. Here we show that Ara‐C‐induced death of cerebellar granule neurons is prevented by an inhibitor of cdk4, whereas inhibition of cdk1, −2 and −5 mimics the death, and non‐cdk4/6 cdks are inhibited by Ara‐C treatment. Cdk1 and −2 are dramatically down‐regulated during neuronal differentiation, and neither Ara‐C nor inhibition of these cdks induces death in mature neurons. This mechanism could also play a significant role in the neurotoxicity associated with the therapeutic use of Ara‐C, as cdk levels can be upregulated in stressed neurons of adult brain. We propose that the balance between cdk4/6 and cdk1/2/5 activity may determine the survival of early differentiating neurons, and that DNA‐damaging agents may induce neuronal death by inhibiting cdk1/2/5 under conditions which require these activities for survival.
The interaction between F3 immunoglobulin domains and protein tyrosine phosphatases ζ/β triggers bidirectional signalling between neurons and glial cells
Authors: Revest Jean‐Michel , Faivre‐Sarrailh Catherine , Maeda Nobuaki , Noda Masaharu , Schachner Melitta , Rougon Geneviève
Published: March 2003

F3, a mouse glycosyl‐phosphatidylinositol anchored molecule of the immunoglobulin superfamily, is known to influence axonal growth and fasciculation via multiple interactions of its modular immunoglobulin‐like domains. We prepared an Fc chimeric molecule (F3IgFc) to identify molecules interacting with these domains and characterize the functional impact of the interactions. We affinity‐isolated tenascin‐C and isoforms of the proteoglycan‐type protein tyrosine phosphatases ζ/β (PTPζ/RPTPβ) from extracts of developing mouse brain. We showed that both PTPζ/RPTPβ and tenascin‐C can bind directly to F3, possibly in an exclusive manner, with the highest affinity for the F3–PTPζ/RPTPβ interaction. We observed a strong binding of F3IgFc‐coated fluorospheres to astrocytes in neural primary cultures and to C6 astrocytoma cells, and demonstrated, in antibody perturbation experiments, that F3‐Ig binding on astrocytes depends on its interaction with PTPζ/RPTPβ. We also found by confocal analysis that tenascin‐C and PTPζ/RPTPβ were colocalized on astrocytes which suggests a complex interplay of interactions between PTPζ/RPTPβ, tenascin‐C and F3. We showed that the interaction between PTPζ/RPTPβ and F3‐Ig‐like domains can trigger bidirectional signalling. C6 glia‐expressed PTPζ/RPTPβ stimulated neurite outgrowth by cortical and cerebellar neurons, whereas preclustered F3IgFc specifically modified the distribution of phosphotyrosine labelling in these glial cells. Both effects could be prevented and/or mimicked by anti‐F3 and anti‐6B4PG antibodies. These results identify F3 and PTPζ/RPTPβ as potential mediators of a reciprocal exchange of information between glia and neurons.
Activation of reward circuitry in human opiate addicts
Authors: Sell L. A. , Morris J. , Bearn J. , Frackowiak R. S. J. , Friston K. J. , Dolan R. J.
Published: March 2003

The neurobiological mechanisms of opiate addictive behaviour in humans are unknown. A proposed model of addiction implicates ascending brainstem neuromodulatory systems, particularly dopamine. Using functional neuroimaging, we assessed the neural response to heroin and heroin‐related cues in established opiate addicts. We show that the effect of both heroin and heroin‐related visual cues are maximally expressed in the sites of origin of ascending midbrain neuromodulatory systems. These context‐specific midbrain activations predict responses to salient visual cues in cortical and subcortical regions implicated in reward‐related behaviour. These findings implicate common neurobiological processes underlying drug and drug‐cue‐related effects.
Selective up‐regulation of P‐ and R‐type Ca2+ channels in rat embryo motoneurons by BDNF
Authors: Baldelli Pietro , Magnelli Valeria , Carbone Emilio
Published: March 2003

Cultured spinal cord motoneurons from day 15 rat embryos (E15) represent a useful model to study Ca2+ channel diversities and their regulation by neurotrophins. Besides the previously identified L‐, N‐ and P‐type channels, E15 rat motoneurons also express high densities of R‐type channels. We have previously shown that the P‐type channel is nearly absent in 60% of these cells, while the R‐type contributes to ≈ 35% of the total current. Here, we show that chronic preincubation of cultured rat motoneurons with high concentrations (20–100 ng/mL) of brain‐derived neurotrophic factor (BDNF) caused a selective up‐regulation of the P‐ and R‐type current density available after blocking N‐ and L‐type channels, with no changes to cell membrane capacitance. N‐ and L‐type channels were either not affected or slightly down‐modulated by the neurotrophin. The onset of BDNF up‐regulation of P/R‐type currents had a half‐time of 12 h and reached maximal values of ≈ 80%. High concentrations of nerve growth factor (NGF; 50–100 ng/mL) had no effect on P/R currents, while BDNF action was prevented by the kinase inhibitor K252a and by the protein synthesis inhibitor anisomycin. These results suggest that chronic applications of BDNF selectively up‐regulates the Ca2+ channel types which are most likely to be involved in the control of neurotransmitter release in mammalian neuromuscular junctions. The signal transduction mechanism is probably mediated by TrkB receptors and involves the synthesis of newly functionally active P‐ and R‐type channels. Our data furnish a rationale for a number of recent observations in other laboratories, in which prolonged applications of neurotrophins were shown to potentiate the presynaptic response in developing synapses.
Direct comparison of projections from the central amygdaloid region and nucleus accumbens shell
Authors: Zahm Daniel S. , Jensen Sarah L. , Williams Evelyn S. , Martin John R.
Published: March 2003

Certain neurochemical and connectional characteristics common to extended amygdala and the nucleus accumbens shell suggest that the two represent a single functional–anatomical continuum. If this is so, it follows that the outputs of the two structures should be substantially similar. To address this, projections from the caudomedial shell and central nucleus of the amygdala, a key extended amygdala structure, were demonstrated in Sprague–Dawley rats with different anterograde axonal tracers processed separately to exhibit distinguishable brown and blue–black precipitates. The caudomedial shell projection is strong in the ventral pallidum and along the medial forebrain bundle through the lateral preopticohypothalamic continuum into the ventral tegmental area, distal to which it thins abruptly. The central nucleus projects strongly to the bed nucleus of the stria terminalis and the sublenticular extended amygdala, but substantially to the lateral hypothalamus only at levels behind the rostral part of the entopeduncular nucleus. Innervation of the ventral tegmental area by the central amygdala is minimal, but the lateral one‐third of the substantia nigra, pars compacta and an adjacent lateral part of the retrorubral field receive substantial central amygdala input. Central amygdaloid projections are robust in caudal brainstem sites, such as the reticular formation, parabrachial nucleus, nucleus of the solitary tract and dorsal vagal complex, all of which receive little input from the accumbens. The substantial differences in the output systems of the caudomedial shell of accumbens and central amygdala suggest that the two represent distinct functional–anatomical systems.
Functional heterogeneity in dopamine release and in the expression of Fos‐like proteins within the rat striatal complex
Authors: Barrot Michel , Marinelli Michela , Abrous Djoher Nora , Rougé‐Pont Françoise , Le Moal Michel , Piazza Pier Vincenzo
Published: March 2003

The dorsolateral striatum, and the core and shell of the nucleus accumbens are three major anatomical regions of the striatal complex. The shell is considered as a part of the extended amygdala, and is involved in the control of motivation and reward. The core and the striatum are considered central to sensory motor integration. In this study we compared the responses of these three regions to mild stress and drugs of abuse by measuring extracellular dopamine (DA) concentrations and Fos‐like immunoreactivity (Fos‐LI). The results are summarrized as follows. (i) In unchallenged conditions, extracellular DA concentrations were highest in the dorsolateral striatum and lowest in the core, whereas Fos‐LI was highest in the shell and lowest in the dorsolateral striatum. (ii) After challenges that increase DA by depolarizing DAergic neurons (injection stress or 2 mg/kg morphine), the shell presented the largest increase in DA levels and Fos‐LI. (iii) After the administration of a DA‐uptake blocker (15 mg/kg cocaine), the percentage increase in DA was still largest in the shell. However, the absolute increase in DA and Fos‐LI in the shell and the dorsolateral striatum were similar. (iv) After a full D1 agonist (SKF82958), Fos‐LI was highest in the shell and lowest in the dorsolateral striatum. In conclusion, the nucleus accumbens shell seems to be the area of the striatal complex most functionally reactive to stress and drugs of abuse. However, the dorsolateral striatum and the core appear functionally distinct, as for most of the parameters studied these two regions differed.
N‐cadherin expression in endothelial cells during early angiogenesis in the eye and brain of the chicken: relation to blood–retina and blood–brain barrier development*
Authors: Gerhardt H. , Liebner S. , Redies C. , Wolburg H.
Published: March 2003

The factors responsible for the induction and maintenance of blood–brain barrier properties are still undefined. The process of blood–brain barrier formation is thought to take place in a two‐stage manner: the initial commitment of vascular sprouts by neuroectodermal cells may be followed by the stabilization of barrier properties. In the present study, we investigated the expression pattern of neural (N)‐cadherin during early angiogenesis in the brain and the pecten oculi of the chicken. The pecten has been introduced previously as a model for the investigation of the formation and maturation of barrier properties in the central nervous system. Whereas perineural and choroid vessels remained immunonegative for N‐cadherin, vascular sprouts invading both the brain and the pecten primordium acquired anti‐N‐cadherin immunoreactivity. Confocal laser scanning and immunoelectron microscopy indicated that the antigen was located at the ablumenal endothelial membrane in contact with subendothelial cells. With the onset of barrier differentiation as determined by junctional restriction of the tight junction protein occludin, N‐cadherin labelling rapidly decreased. Specific intraneuroectodermal upregulation and decline of endothelial N‐cadherin was confirmed by in situ hybridization and suggests that N‐cadherin expression by cerebral and pecteneal endothelial cells represents an initial and transient signal which may be involved in the commitment of early blood vessels to express blood–brain and blood–retina barrier properties.
Incorporation of a gephyrin‐binding motif targets NMDA receptors to gephyrin‐rich domains in HEK 293 cells
Authors: Kins Stefan , Kuhse Jochen , Laube Bodo , Betz Heinrich , Kirsch Joachim
Published: March 2003

The peripheral membrane protein gephyrin is essential for the postsynaptic localization of inhibitory glycine receptors (GlyRs). Binding of gephyrin to the GlyR β subunit is mediated by a sequence motif located in the intracellular loop region connecting transmembrane segments 3 and 4. Here, insertion of this binding motif is shown to alter the subcellular distribution of an excitatory neurotransmitter receptor in transfected mammalian cells. Upon coexpression with gephyrin, a mutant N‐methyl‐d‐aspartate (NMDA) receptor containing NMDA receptor 1 (NR1) subunits which harboured a gephyrin‐binding motif within its cytoplasmic tail region, was targeted to intracellular gephyrin‐rich domains, as previously observed for the GlyR β subunit. Our data indicate that a gephyrin‐binding motif located in a cytoplasmic domain of an integral membrane protein suffices for routing to gephyrin‐rich domains.
Excitatory synaptic inputs to pyramidal neurons of the lateral amygdala
Authors: Mahanty Nishith K. , Sah Pankaj
Published: March 2003

Whole‐cell patch clamp recordings were made from pyramidal neurons in the rat lateral amygdala (LA). Synaptic currents were evoked by stimulating in either the external capsule (ec), internal capsule (ic) or basolateral nucleus (BLA). Stimulation of either the ic, ec or BLA evoked a glutamatergic excitatory synaptic current (EPSC) which was mediated by both non‐NMDA and NMDA (N‐methyl‐d‐aspartic acid) receptors. The ratio of the amplitude of the NMDA receptor‐mediated component measured at +40 mV to the amplitude of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) component measured at −60 mV was similar regardless of whether EPSCs were evoked in the ec, ic or BLA. At resting membrane potentials, excitatory synaptic potentials evoked from either the ec or putative thalamic inputs were unaffected by application of the NMDA receptor antagonist APV. Spontaneous glutamatergic currents had two components to their decay phase. The slow component was selectively blocked by the NMDA receptor antagonist D‐APV, indicating that AMPA and NMDA receptors are colocalized in spiny neurons. We conclude that pyramidal cells of the LA receive convergent inputs from the cortex, thalamus and basal nuclei. At all inputs, both AMPA/kainate and NMDA‐type receptors are active and colocalized in the postsynaptic density.