bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal characterization of memory retrieval processes: an fMRI study of the ‘tip of the tongue’ phenomenon
Authors: Kikyo Hideyuki , Ohki Kenichi , Sekihara Kensuke
Published: March 2003

‘Tip of the tongue’ (TOT) is a natural phenomenon in which people cannot retrieve a target word immediately, even though they feel confident that they know the target. This provides us an opportunity to understand the human memory system, because cognitive components of memory retrieval such as retrieval effort and successful retrieval are temporally dissociated from each other during the TOT states. The purpose of the present study was to reveal the neural correlates of the cognitive components of the retrieval process by separating cognitive phases of the TOT phenomenon using event‐related functional magnetic resonance imaging with multiple regression analysis. We demonstrated that the left dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex were activated at the time of successful retrieval, and the left DLPFC also showed activation when the subjects successfully retrieved the target names as compared to when they gave up. This result suggests that the left DLPFC is specific to the successful retrieval process. During the TOT state, a number of regions were activated, and this suggests that widely distributed brain regions are engaged when people make a hard effort to retrieve a proper name in the TOT state. Our new approach employing temporal resolution of the TOT phenomenon may contribute to the understanding of the mechanisms of the human memory system.
Striatal projections from the cat visual thalamus
Authors: Harting John K. , Updyke Bruce V. , Van Lieshout David P.
Published: March 2003

Anterograde transport methods reveal an extensive thalamostriate projection from the extrageniculate visual thalamus. These projections distribute to approximately the same regions of the striatum innervated by the corticostriate projections from over a dozen higher visual cortical areas [visual‐recipient sector; Updyke, B.V. (1993) J. Comp. Neurol., 327, 159–193.]. Like their cortical counterparts, the thalamostriate projections to the caudate distribute in a patchy manner that suggests potential overlap or intermingling spatial relationships between the two major afferents. All of the visually related thalamic nuclei projecting to the striatum receive ascending signals from the superior colliculus, suggesting that the constraints placed upon tectal processing by striatonigral control have important consequences for central perceptuomotor processing at the striatal and cortical levels.
Caspase inhibitors increase short‐term survival of progenitor‐cell progeny in the adult rat dentate gyrus following status epilepticus
Authors: Ekdahl Christine T. , Mohapel Paul , Elmér Eskil , Lindvall Olle
Published: March 2003

The dentate gyrus (DG) is one of the few regions in the brain that continues to produce new neurons throughout adulthood. Seizures not only increase neurogenesis, but also lead to death of DG neurons. We investigated the relationship between cell death and neurogenesis following seizures in the DG of adult rats by blocking caspases, which are key components of apoptotic cell death. Multiple intracerebroventricular infusions of caspase inhibitors (pancaspase inhibitor zVADfmk, and caspase 3 and 9 inhibitor) prior to, just after, 1 day after, and 1 week following 2 h of lithium–pilocarpine‐induced status epilepticus reduced the number of terminal deoxynucleotidyl transferase‐mediated fluorescein‐dUTP nick‐end labelled (TUNEL) cells and increased the number of bromodeoxyuridine (BrdU) ‐stained proliferated cells in the subgranular zone at 1 week. The caspase inhibitor‐treated group did not differ from control at 2 days or 5 weeks following the epileptic insult. Our findings suggest that caspases modulate seizure‐induced neurogenesis in the DG, probably by regulating apoptosis of newly born neurons, and that this action can be suppressed transiently by caspase inhibitors. Furthermore, although previous studies have indicated that increased neuronal death can trigger neurogenesis, we show here that reduction in apoptotic death may be associated with increased neurogenesis.
ATP stimulation of P2X7 receptors activates three different ionic conductances on cultured mouse Schwann cells
Authors: Colomar Aurore , Amédée Thierry
Published: March 2003

Extracellular ATP, by acting on P2 purinergic receptors, is a potent mediator of cell‐to‐cell communication both within and between the nervous and the immune systems. We show here by patch‐clamp recording, fluorescent dye uptake and immunocytochemistry that, in cultured mouse Schwann cells, ATP activates a P2X7 receptor associated with three different ionic conductances. In control conditions, ATP activated an inward current (IATP) with a low potency (EC50, 7.2 mm). Replacing ATP either by the ATP analogue 2′,3′‐O‐(4‐benzoyl‐4‐benzoyl)‐ATP (BzATP) or by the tetraacidic form ATP4– potentiated the inward current (ATP4– EC50, 375 µm). ATP and BzATP currents were strongly reduced by periodate oxidized ATP (oATP), an antagonist of P2X7 receptors. IATP was a mixed current composed of a nonselective cationic conductance, a cationic conductance selective for K+ and an anionic conductance selective for Cl–. The activation of the K+ conductance was dependent on an influx of Ca2+, and was blocked by charybdotoxin (ChTX) and tetraethylammonium (TEA), two potent antagonists of large conductance Ca2+‐activated K+ channels (BK channels). The activation of the Cl– conductance was insensitive to Ca2+ but required the presence of K+. Total removal of K+ blocked both the Ca 2+‐activated K+ conductance and the Cl– conductance, unveiling the P2X7 nonselective cationic conductance. The P2X7 receptor was localized by immunocytochemistry using a polyclonal antibody, anti‐P2X7, whilst its expression and functionality were both detected by the uptake of Lucifer Yellow. This receptor could regulate the synthesis and the release of cytokines by Schwann cells during pathophysiological events.
Immobilized amyloid precursor protein constructs: a tool for the in vitro screening of glial cell reactivity
Authors: Von Bernhardi Rommy , Ramírez Gigliola , Matile Hugues , Döbeli Heinz
Published: March 2003

Astrocytes and microglia are closely associated with amyloid plaques in Alzheimer's disease (AD). Microglia constitute the first barrier surrounding plaques, although they seem to be unable to remove them efficiently. We evaluated the reaction of microglial cells from neonatal rats and mice to plaque mimetics. The C‐terminal part of the amyloid precursor protein (APP) or amyloid peptide (Aβ) was immobilized to either 60‐µm or 2.8‐µm beads and incubated with microglial cells. Beads of 60 µm, having approximately the size of senile plaques, were not phagocytosed, in contrast to 2.8‐µm beads, which were phagocytosed by microglia but not by astrocytes. Once taken up by the cells, proteins immobilized to the beads were degraded rapidly, as confirmed by mass spectrometry and immunofluorescence with an antibody against β‐amyloid. On the other hand, no protein degradation was observed with 60‐µm beads. Also, probably as a reaction to its incapability to phagocytose the beads, glia organized around the beads and started to proliferate. Cell proliferation was more pronounced when the beads contained the Aβ epitope compared with the beads with an inert surface. This in vitro effect could be exploited to set up a screening assay for compounds that ameliorate the adverse reaction of microglia supposed to contribute to the pathogenesis of AD.
Strain differences in the behavioural outcome of neonatal ventral hippocampal lesions are determined by the postnatal environment and not genetic factors
Authors: Wood Graham K. , Marcotte Eric R. , Quirion Remi , Srivastava Lalit K.
Published: March 2003

It has been demonstrated that not only do rats neonatally lesioned in the ventral hippocampus (VH) develop behavioural hypersensitivity to amphetamine postpubertally, but also that the expression of the sensitivity is strain specific. For example, excitotoxic VH lesions at postnatal day (PD) 7 lead to significant increases in amphetamine‐induced locomotion in postpubertal Fischer rats, but not in Lewis rats. However, as it is likely that the effect of strain differences are due to a combination of genetics and environment, we examined the contributions of the environment of the pups in determining the behavioural outcome following neonatal VH lesions. Fisher and Lewis rat pups were cross‐fostered at birth, and then at PD7 lesioned bilaterally in the VH with ibotenic acid. anova analysis of postpubertal amphetamine‐induced locomotor data revealed a significant effect of the strain of the dams raising the pups but no effect of the strain of the pup. In addition, a post hoc analysis revealed that lesioned Fisher or Lewis rats raised by Fisher, but not those raised by Lewis, dams demonstrated amphetamine‐induced hyperlocomotion relative to nonlesioned controls. Observations of the maternal behaviour of Fischer and Lewis dams revealed significant differences in the frequency of arched‐back nursing between the two strains. Interestingly, a correlation of the frequency of arched back nursing vs novelty‐ or amphetamine‐induced locomotion revealed that the lesioned rats were significantly more affected by increases in arched‐back nursing compared to the controls. The results suggest that the genetic background of the pups does not significantly affect the behavioural outcome following neonatal VH lesions; however, the results do suggest an important role of early environmental variables on the behavioural outcome of neonatal VH lesions.
Detection of animals in natural images using far peripheral vision
Authors: Thorpe Simon J. , Gegenfurtner Karl R. , Fabre‐Thorpe Michèle , Bülthoff Heinrich H.
Published: March 2003

It is generally believed that the acuity of the peripheral visual field is too poor to allow accurate object recognition and, that to be identified, most objects need to be brought into foveal vision by using saccadic eye movements. However, most measures of form vision in the periphery have been done at eccentricities below 10° and have used relatively artificial stimuli such as letters, digits and compound Gabor patterns. Little is known about how such data would apply in the case of more naturalistic stimuli. Here humans were required to categorize briefly flashed (28 ms) unmasked photographs of natural scenes (39° high, and 26° across) on the basis of whether or not they contained an animal. The photographs appeared randomly in nine locations across virtually the entire extent of the horizontal visual field. Accuracy was 93.3% for central vision and decreased almost linearly with increasing eccentricity (89.8% at 13°, 76.1% at 44.5° and 71.2% at 57.5°). Even at the most extreme eccentricity, where the images were centred at 70.5°, subjects scored 60.5% correct. No evidence was found for hemispheric specialization. This level of performance was achieved despite the fact that the position of the image was unpredictable, ruling out the use of precued attention to target locations. The results demonstrate that even high‐level visual tasks involving object vision can be performed using the relatively coarse information provided by the peripheral retina.
Effect of vasopressin on the input–output properties of rat facial motoneurons
Authors: Pierson Patricia , Tribollet Eliane , Raggenbass Mario
Published: March 2003

Vasopressin can directly excite facial motoneurons in young rats and mice. It acts by generating a persistent inward current, which is Na+‐dependent, tetrodotoxin‐insensitive and voltage‐gated. This peptide‐evoked current is unaffected by Ca++ or K+ channel blockade and is modulated by extracellular divalent cations. In the present work, we determined how vasopressin alters the input–output properties of facial motoneurons. Whole‐cell recordings were obtained from these neurons in the current clamp mode, in brainstem slices of young rats. Repetitive firing was evoked by injecting depolarizing current pulses. Steady‐state frequency–current (f–I) relationships were constructed and the effect of vasopressin on these relationships was studied. We found that vasopressin caused a parallel shift to the left of the cell steady‐state f–I relationship. This effect persisted in the presence of blockers of K+ or Ca++ channels. The peptide effect was distinct from that brought about by Ca++ channel suppression or by apamin, a blocker of the mAHP. These latter manipulations resulted in an increase in the slope of the steady‐state f–I relationship. We conclude that the vasopressin‐induced modification of the input–output properties of facial motoneurons is probably exclusively caused by the sodium‐dependent, voltage‐modulated inward current elicited by the peptide, rather than being due to indirect effects of the peptide on Ca++ channels, K+ channels or Ca++‐dependent K+ channels. Computer simulation, based on a simple model of facial motoneurons, indicates that the introduction of a conductance having the properties of the vasopressin‐dependent conductance can entirely account for the observed peptide‐induced shift of the f–I relationship.
Evaluation of the tetracycline‐ and ecdysone‐inducible systems for expression of neurotransmitter receptors in mammalian cells
Authors: Van Craenenbroeck Kathleen , Vanhoenacker Peter , Leysen Josée E. , Haegeman Guy
Published: March 2003

Establishing a stable cell line that expresses a particular protein of interest is often a laborious and time‐consuming experience. With constitutive expression systems, a gradual loss of the highly expressing clones over a given time span and/or a severe counter‐selection due to toxicity of the expressed protein for the host cell line are major drawbacks. In both cases, inducible expression systems offer a valuable alternative. Over the years, many regulated expression systems have been developed and evaluated. In the present study, we compare the efficiency, the advantages and the drawbacks of a tetracycline‐ and an ecdysone‐inducible system for expression of the reporter protein chloramphenicol acetyltransferase and of different G‐protein‐coupled serotonin (5‐HT) receptors. A high level of expression of different 5‐HT receptors was obtained with the tetracycline‐inducible system. In the cell line L929, which stably expresses the tetracycline‐responsive transactivator, a maximum ligand binding of 20 000 and 9500 fmol/mg protein was measured for the h5‐HT1B and h5‐ht1F receptors, respectively. In the HEK293rtTA cell line, levels of 15 700, 3000, and 9100 fmol bound ligand/mg protein were obtained for the h5‐HT1B, h5‐ht1F and h5‐HT4b receptors, respectively. These high expression levels remained stable for several months of continuous culture. Although the ecdysone‐inducible expression system was useful for tightly regulated expression, the levels were far lower than those obtained with the tetracycline system (e.g. 640 fmol bound ligand/mg protein for the h5‐ht1F receptor in HEK293EcR).
Impairment of binocular vision in the adult cat induces plastic changes in the callosal cortical map
Authors: Watroba Laurent , Buser Pierre , Milleret Chantal
Published: March 2003

In the primary visual cortex of normally reared adult cat, neurons activated through the corpus callosum are almost entirely located at the 17/18 border. They display small receptive fields distributed along the central vertical meridian of the visual field and are orientation selective. Here we demonstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size mainly toward the ipsilateral hemifield and to a loss of their orientation selectivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the result of the strengthening of normally hidden subthreshold synaptic inputs.
Dopamine inhibition of auditory nerve activity in the adult mammalian cochlea
Authors: Ruel Jérôme , Nouvian Régis , D'Aldin Christine Gervais , Pujol Rémy , Eybalin Michel , Puel Jean‐Luc
Published: March 2003

Efferent feedback systems provide a means for modulating the input to the central nervous system. The lateral olivocochlear efferents modulate auditory nerve activity via synapses with afferent dendrites below sensory inner hair cells. We examined the effects of dopamine, one of the lateral olivocochlear neurotransmitters, by recording compound and single unit activity from the auditory nerve in adult guinea pigs. Intracochlear application of dopamine reduced the compound action potential (CAP) of the auditory nerve, increased the thresholds and decreased the spontaneous and driven discharge rates of the single unit fibres without changing their frequency‐tuning properties. Surprisingly, dopamine antagonists SCH‐23390 and eticlopride decreased CAP amplitude as did dopamine. In some units, both SCH‐23390 and eticlopride increased the basal activity of auditory nerve fibres leading to an improvement of threshold sensitivity and a decrease of the maximum driven discharge rates to sound. In other units, the increase in firing rate was immediately followed by a marked reduction to values below predrug rates. Because CAP reflects the summed activity of auditory nerve fibres discharging in synchrony, both the decrease in sound‐driven discharge rate and the postexcitatory reduction account for the reduction in CAP. Ultrastructural examination of the cochleas perfused with eticlopride showed that some of the afferent dendrites were swollen, suggesting that the marked reduction in firing rate may reflect early signs of excitotoxicity. Results suggest that dopamine may exert a tonic inhibition of the auditory nerve activity. Removal of this tonic inhibition results in the development of early signs of excitotoxicity.
Phosphorylation of voltage‐gated ion channels in rat olfactory receptor neurons
Authors: Wetzel Christian H. , Spehr Marc , Hatt Hanns
Published: March 2003

In olfactory receptor neurons (ORNs), ligand–odorant receptor interactions cause G protein‐mediated activation of adenylate cyclase and a subsequent increase in concentration of the intracellular messenger cAMP. Odorant‐evoked elevation in cAMP is thought to directly activate a cation‐selective cyclic nucleotide‐gated channel, which causes external Ca2+ influx, leading to membrane depolarization and the generation of action potentials. Our data show that in freshly dissociated rat ORNs, odorant‐induced elevation in cAMP also activates cAMP‐dependent protein kinase (PKA), which is then able to phosphorylate various protein targets in the olfactory signal transduction pathway, specifically voltage‐gated sodium and calcium channels. The presence of PKI (PKA inhibitor peptide) blocked the modulatory action of cAMP on voltage‐gated ion channels. By modulating the input/output properties of the sensory neurons, this mechanism could take part in the complex adaptation process in odorant perception. In addition, we found modulation of voltage‐gated sodium and calcium channel currents by 5‐hydroxytryptamine and the dopamine D1 receptor agonist SKF 38393. These findings suggest that in situ ORNs might also be a target for efferent modulation.
Potentially epileptogenic dysfunction of cortical NMDA‐ and GABA‐mediated neurotransmission in Otx1–/– mice
Authors: Sancini G. , Franceschetti S. , Lavazza T. , Panzica F. , Cipelletti B. , Frassoni C. , Spreafico R. , Acampora D. , Avanzini G.
Published: March 2003

Knockout Otx1 mice present a microcephalic phenotype mainly due to reduced deep neocortical layers and spontaneous recurrent seizures. We investigated the excitable properties of layer V pyramidal neurons in neocortical slices prepared from Otx1–/– mice and age‐matched controls. The qualitative firing properties of the neurons of Otx1–/– mice were identical to those found in wild‐type controls, but the proportion of intrinsically bursting (IB) neurons was significantly smaller. This is in line with the lack of the Otx1 gene contribution to the generation and differentiation of neurons destined for the deep neocortical layers, in which IB neurons are located selectively in wild‐type rodents. The pyramidal neurons recorded in Otx1–/– mice responded to near‐threshold electrical stimulation of the underlying white matter, with aberrant polysynaptic excitatory potentials often leading to late action potential generation. When the strength of the stimulus was increased, the great majority of the Otx1–/– neurons (78%) responded with a prominent biphasic inhibitory postsynaptic potential that was significantly larger than that observed in the wild‐type mice, and was often followed by complex postinhibitory depolarizing events. Both late excitatory postsynaptic potentials and postinhibitory excitation were selectively suppressed by NMDA receptor antagonists, but not by AMPA antagonists. We conclude that the cortical abnormalities of Otx1–/– neocortex due to a selective loss of large projecting neurons lead to a complex rearrangement of local circuitry, which is characterized by an excess of N‐methyl‐d‐aspartate‐mediated polysynaptic excitation that is counteracted by GABA‐mediated inhibition in only a limited range of stimulus intensity. Prominent postsynaptic inhibitory potentials may also act as a further pro‐epileptogenic event by synchronizing abnormal excitatory potentials.
Impaired water maze learning performance without altered dopaminergic function in mice heterozygous for the GDNF mutation
Authors: Gerlai R. , McNamara A. , Choi‐Lundberg D. L. , Armanini M. , Ross J. , Powell‐Braxton L. , Phillips H. S.
Published: March 2003

Exogenous glial cell line‐derived neurotrophic factor (GDNF) exhibits potent survival‐promoting effects on dopaminergic neurons of the nigrostriatal pathway that is implicated in Parkinson's disease and also protects neurons in forebrain ischemia of animal models. However, a role for endogenous GDNF in brain function has not been established. Although mice homozygous for a targeted deletion of the GDNF gene have been generated, these mice die within hours of birth because of deficits in kidney morphogenesis, and, thus, the effect of the absence of GDNF on brain function could not be studied. Herein, we sought to determine whether adult mice, heterozygous for a GDNF mutation on two different genetic backgrounds, demonstrate alterations in the nigrostriatal dopaminergic system or in cognitive function. While both neurochemical and behavioural measures suggested that reduction of GDNF gene expression in the mutant mice does not alter the nigrostriatal dopaminergic system, it led to a significant and selective impairment of performance in the spatial version of the Morris water maze. A standard panel of blood chemistry tests and basic pathological analyses did not reveal alterations in the mutants that could account for the observed performance deficit. These results suggest that endogenous GDNF may not be critical for the development and functioning of the nigrostriatal dopaminergic system but it plays an important role in cognitive abilities.
Fluctuation of extracellular hypocretin‐1 (orexin A) levels in the rat in relation to the light–dark cycle and sleep–wake activities
Authors: Yoshida Y. , Fujiki N. , Nakajima T. , Ripley B. , Matsumura H. , Yoneda H. , Mignot E. , Nishino S.
Published: March 2003

Hypocretins/orexins are neuropeptides implicated in sleep regulation and the sleep disorder narcolepsy. In order to examine how hypocretin activity fluctuates across 24 h with respect to the sleep–wake cycle, we measured changes in extracellular hypocretin‐1 levels in the lateral hypothalamus and medial thalamus of freely moving rats with simultaneous sleep recordings. Hypocretin levels exhibited a robust diurnal fluctuation; levels slowly increased during the dark period (active phase), and decreased during the light period (rest phase). Levels were not correlated with the amount of wake or sleep in each period. Although an acute 4‐h light‐shift did not alter hypocretin levels, 6‐h sleep deprivation significantly increased hypocretin release during the forced‐wake period. Hypocretin activity is, thus, likely to build up during wakefulness and decline with the occurrence of sleep. These findings, together with the fact that a difficulty in maintaining wakefulness during the daytime is one of the primary symptoms of hypocretin‐deficient narcolepsy, suggest that hypocretin activity may be critical in opposing sleep propensity during periods of prolonged wakefulness.
Auditory and vestibular defects in the circling (ci2) rat mutant
Authors: Kaiser Alexander , Fedrowitz Maren , Ebert Ulrich , Zimmermann Elke , Hedrich Hans‐Jürgen , Wedekind Dirk , Löscher Wolfgang
Published: March 2003

The circling rat is an autosomal recessive mutant (homozygous ci2/ci2) that displays lateralized circling behaviour, locomotor hyperactivity, ataxia and stereotypic head‐movement. These abnormal behaviours occur in phases or bursts either spontaneously or in response to stress. Heterozygous (ci2/+) littermates display normal spontaneous behaviours. We have previously found that ci2/ci2 rats of both genders have a lower tissue content of dopamine in the striatum ipsilateral to the preferred direction of rotation, indicating that the rats turn away from the brain hemisphere with higher striatal dopaminergic activity. In view of the similarities of the motor syndrome of the ci2/ci2 mutant rat to that of mouse deafness mutants, the present study evaluated the hearing ability of the circling rat mutant by recording brainstem auditory‐evoked potentials. To test for vestibular dysfunction, a swimming test was conducted. Histological methods were used to examine the cochlear and vestibular parts of the inner ear and the cochlear and vestibular brainstem nuclei for defects. The absence of auditory‐evoked potentials demonstrated a complete hearing loss in the adult ci2/ci2 mutant rat, whereas heterozygous littermates exhibited auditory‐evoked potentials with thresholds resembling those of other laboratory strains. Furthermore, the mutant rats were unable to swim. Histological analysis of the inner ear of adult mutants revealed virtually complete loss of the cochlear neuroepithelium, while no such hair cell degeneration was seen in the vestibular parts of the inner ear. However, part of the vestibular hair cells showed protrusions into the endolymphatic space, suggesting alterations in the cytoskeletal architecture. The histological findings in mutant circling rats strongly indicate that the hearing loss of the mutants is of the sensory neural type, the most prevalent type of hearing loss. In the cochlear nuclei of the brain stem of mutant rats, neurons exhibited an abnormal shape, reduced size and increased density compared to controls. In contrast, no abnormal neuronal morphology was seen in the vestibular nuclei, but a significantly reduced neuronal density was found in the medial vestibular nucleus. Abnormal vestibular function would be a likely explanation for the disturbed balance of mutant rats as exemplified by the ataxia and the inability to swim, whereas the previous data on these rats strongly indicate an involvement of the basal ganglia in the abnormal circling behaviour. The genetic defect in the mutant rats, thus, results in a clinical syndrome with features also seen in human genetic disorders with deafness and hyperkinesia, making the ci2/ci2 rat an excellent model for investigating both cochlear/vestibular dysfunction and hyperkinetic movement disorders.
Molecular cloning and dendritic localization of rat SH3P7
Authors: Yamazaki Hiroyuki , Takahashi Hideto , Aoki Takeo , Shirao Tomoaki
Published: March 2003

SH3P7 was originally isolated by cloning SH3 domain ligand targets from a mouse embryo cDNA library. SH3P7 is an actin‐binding protein implicated in antigen reception, JNK1 signalling, and Rac activation. It contains a drebrin homology sequence in its N‐terminal region and a cortactin homology sequence (SH3 domain) in its C‐terminal region. Both drebrin and cortactin are actin‐binding proteins, and both have been suggested as possible regulators of the actin cytoskeleton in neurons. In the present study, we performed cDNA cloning of rat SH3P7, performed RT‐PCR analysis, generated polyclonal antibodies against the recombinant rat SH3P7 protein, and examined the distribution of SH3P7 in the rat brain using immunohistochemistry. Sequence analysis revealed that there were at least four isoforms of the SH3P7 protein: SH3P7r1–SH3P7r4. RT‐PCR analysis revealed that the predominant isoforms expressed in the brain were SH3P7r1 and SH3P7r3. The relative levels of isoform expression were similar among regions. Immunohistochemistry revealed that the most intense immunolabelling for SH3P7 was observed in the hippocampus and cerebellar cortex. Double‐labelling studies with anti‐SH3P7 antibody and other neuronal marker proteins revealed that SH3P7 was located primarily in dendrites, and in moderate amounts in cell bodies. Immunoreactivity was absent in the presynaptic terminals. In cultured astrocytes, SH3P7 was localized at protrusive structures of the cell periphery and in the cell body. We concluded that SH3P7 is ubiquitous in the rat brain, and occurs as several isoforms. Also, its dendritic localization suggests that SH3P7 is functionally linked to actin cytoskeleton organization in dendrites.
Distinct properties and differential β subunit regulation of two C‐terminal isoforms of the P/Q‐type Ca2+‐channel α1A subunit
Authors: Sandoz Guillaume , Bichet Delphine , Cornet Veronique , Mori Yasuo , Felix Ricardo , De Waard Michel
Published: March 2003

Two C‐terminal splice variants (BI‐1 and BI‐2, now termed Cav2.1a and Cav2.1b) of the neuronal voltage‐gated P/Q‐type Ca2+ channel α1A pore‐forming subunit have been cloned (Mori et al., 1991, Nature, 350, 398–402). BI‐1 and BI‐2 code for proteins of 2273 and 2424 amino acids, respectively, and differ only by their extreme carboxyl‐termini sequences. Here, we show that, in Xenopus oocytes, the two isoforms direct the expression of channels with different properties. Electrophysiological analysis showed that BI‐1 and BI‐2 have peak Ba2+ currents (IBa) at a potential of +30 and +20 mV, respectively. The different C‐terminal sequence (amino acids 2229–2273) of BI‐1 caused a shift in steady‐state inactivation by +10 mV and decreased the proportion of fast component of current inactivation twofold. Likewise, the biophysical changes in IBa caused by coexpression of the β4 auxiliary subunit were substantially different in BI‐1‐ and BI‐2‐containing channels in comparison to those induced by β3. Several of these differences in β regulation were abolished by deleting the carboxyl‐terminal splicing region. By creating a series of GST fusion proteins, we identified two locations in the C‐terminal (Leu2090–Gly2229 for BI‐1 and BI‐2, and Arg2230–Pro2424 for BI‐2 only) that determine the differential interaction of β4 with the distinct α1A isoforms. These interactions appear to favour the binding of β4 to the AID site, and also the plasma membrane expression of BI‐2. These results demonstrate that the final segment of the C‐terminal affects α1A channel gating, interaction and regulation with/by the β subunits. The data will have several implications for the understanding of the biophysical effects of many channelopathies in which the carboxyl‐termini of α1A and β4 are affected.
Taurine selectively modulates the secretory activity of vasopressin neurons in conscious rats
Authors: Engelmann Mario , Ludwig Mike , Singewald Nicolas , Ebner Karl , Sabatier Nancy , Lubec Gert , Landgraf Rainer , Wotjak Carsten T.
Published: March 2003

Previous experiments have shown that a 10‐min forced swimming session triggers the release of vasopressin from somata and dendrites, but not axon terminals, of neurons of the hypothalamic–neurohypophysial system. To further investigate regulatory mechanisms underlying this dissociated release, we forced male Wistar rats to swim in warm (20 °C) water and monitored release of the potentially inhibitory amino acids gamma amino butyric acid (GABA) and taurine into the hypothalamic supraoptic nucleus using microdialysis. Forced swimming caused a significant increase in the release of taurine (up to 350%; P < 0.05 vs. prestress release), but not GABA. To reveal the physiological significance of centrally released taurine, the specific taurine antagonist 6‐aminomethyl‐3‐methyl‐4H‐1,2,4‐benzothiadiazine‐1,1‐dioxide was administered into the supraoptic nucleus via retrodialysis. Administration of this antagonist caused a significant increase in the release of vasopressin within the supraoptic nucleus and into the blood both under basal conditions and during stress (up to 800%; P < 0.05 vs. basal values), without affecting hypothalamic or plasma oxytocin. Local administration of the GABAA receptor antagonist bicuculline, in contrast, failed to influence vasopressin secretion at either time point. In a separate series of in vivo electrophysiological experiments, administration of the same dosage of the taurine antagonist into the supraoptic nucleus via microdialysis resulted in an increased electrical activity of identified vasopressinergic, but not oxytocinergic, neurons. Taken together our data demonstrate that taurine is released within the supraoptic nucleus during physical/emotional stress. Furthermore, at the level of the supraoptic nucleus, taurine inhibits not only the electrical activity of vasopressin neurons but also acts as an inhibitor of both central and peripheral vasopressin secretion during different physiological states.
Subunit composition of strychnine‐sensitive glycine receptors expressed by adult rat basolateral amygdala neurons
Authors: McCool Brian A. , Farroni Jeffery S.
Published: March 2003

In neonatal rats, strychnine‐sensitive glycine receptors are widely expressed in the spinal cord, brainstem and forebrain. During development, these ‘neonatal’ receptors are replaced by an adult isoform, the expression of which becomes restricted primarily to brain stem and spinal cord. Unlike most forebrain regions, functional strychnine‐sensitive glycine receptors appear to persist within adult rat amygdala. However, the subunit composition of glycine receptors expressed by amygdala neurons and its relationship to the adult isoform in brain stem/spinal cord has not been defined precisely. In this report, we have utilized RT‐PCR and single‐cell RT‐PCR to demonstrate that the ‘neonatal’α2‐subunit mRNA persists in adult rat amygdala neurons and is the predominant α‐subunit. We further demonstrate that native amygdala glycine receptors are relatively insensitive to the receptor antagonist picrotoxin, suggesting that α2‐ and β‐subunits may be present together in the same multisubunit complex. We further demonstrate that α2‐ and β‐subunits cloned from adult rat amygdala can form functional channels when expressed in a heterologous system. Together, these studies highlight both the unique characteristics of strychnine‐sensitive glycine receptors in the adult rat amygdala as well as the possibility that α2/β channels may represent the adult forebrain isoform of the strychnine‐sensitive glycine receptor.
Chronic morphine exposure increases the phosphorylation of MAP kinases and the transcription factor CREB in dorsal root ganglion neurons: an in vitro and in vivo study
Authors: Ma Weiya , Zheng Wen‐Hua , Powell Kelly , Jhamandas Khem , Quirion Remi
Published: March 2003

Tolerance to opiates reduces their effectiveness in the treatment of severe pain. Although the mechanisms are unclear, overactivity of pro‐nociceptive systems has been proposed to contribute to this phenomenon. We have reported that the development of morphine tolerance significantly increased calcitonin‐gene‐related‐peptide‐like immunoreactivity (CGRP‐IR) in primary sensory afferents of the spinal dorsal horn, suggesting that changes in pain‐related neuropeptides in the dorsal root ganglion (DRG) neurons may be involved (Menard et al., 1996, J. Neurosci., 16, 2342–2351). Recently, we have shown that repeated morphine treatments induced increases in CGRP‐ and substance P (SP)‐IR in cultured DRG, mimicking the in vivo effects (Ma et al., 2000, Neuroscience, 99, 529–539). In this study, we investigated the intracellular signal transduction pathways possibly involved in morphine‐induced increases in CGRP‐ and SP‐IR in DRG neurons. Repeated morphine exposure (10–20 µm) for 6 days increased the number of neurons expressing phosphorylated (p) mitogen‐activated protein (MAP) kinases, including the extracellular signal‐regulated kinase (pERK), c‐jun N‐terminal kinase (pJNK) and P38 (pP38 MAPK). The number of neurons expressing phosphorylated cAMP responsive element binding protein (pCREB) was also markedly increased in morphine‐exposed cultured DRG neurons. pERK‐, pP38‐, pJNK‐ and pCREB‐IR were colocalized with CGRP‐IR in cultured DRG neurons. Naloxone effectively blocked these actions of morphine, whereas a selective MEK1 inhibitor, PD98059, inhibited the morphine‐induced increase in the phosphorylation of ERK and CREB, and the expression of CGRP and SP. Moreover, in morphine‐tolerant rats, the number of pCREB‐, CGRP‐ and SP‐IR neurons in the lumbar DRG was also significantly increased. These in vitro and in vivo data suggest that the phosphorylation of MAP kinases and CREB plays a role in the morphine‐induced increase in spinal CGRP and SP levels in primary sensory afferents, contributing to the development of tolerance to opioid‐induced analgesia.
Behavioural rhythm splitting in the CS mouse is related to clock gene expression outside the suprachiasmatic nucleus
Authors: Abe Hiroshi , Honma Sato , Namihira Masakazu , Masubuchi Satoru , Honma Ken‐ichi
Published: March 2003

CS mice exhibit a spontaneous splitting in the circadian rhythm of locomotor activity under constant darkness, suggesting that they contain two weakly coupled oscillators in the circadian clock system regulating locomotor activity rhythm. In order to clarify whether the two oscillators are located in the suprachiasmatic nucleus (SCN), a site of the master circadian pacemaker in mammals, circadian rhythms in mRNA of mousePeriodgenes (mPer1,mPer2andmPer3) in the SCN and cerebral cortex were examined during rhythm splitting byin situhybridization. In the SCN,mPer1andmPer2showed a circadian rhythm with a single peak in both split and unsplit mice. The rhythms ofmPer1andmPer2were slightly phase delayed during rhythm splitting in reference to the activity onset, but the phase relationship between the two rhythms was not changed. In the cerebral cortex, the expression ofmPer1andmPer2underwent the bimodal fluctuation with peaks temporally corresponding to split activity components. The unsplit mice showed the circadian rhythms with a single peak. There was no difference in themPer3rhythms in either the SCN or the cerebral cortex between the split and unsplit mice. These results indicate that the circadian oscillations ofmPer1,mPer2andmPer3in the SCN are not related to the rhythm splitting of CS mice. The split rhythms of the CS mice are suggested to be caused by uncoupling of oscillators located outside the SCN from the SCN circadian pacemaker.
Stressor categorization: acute physical and psychological stressors elicit distinctive recruitment patterns in the amygdala and in medullary noradrenergic cell groups
Authors: Dayas C.V. , Buller K.M. , Crane J.W. , Xu Y. , Day T.A.
Published: March 2003

It has been hypothesized that the brain categorizes stressors and utilizes neural response pathways that vary in accordance with the assigned category. If this is true, stressors should elicit patterns of neuronal activation within the brain that are category‐specific. Data from previous immediate–early gene expression mapping studies have hinted that this is the case, but interstudy differences in methodology render conclusions tenuous. In the present study, immunolabelling for the expression of c‐fos was used as a marker of neuronal activity elicited in the rat brain by haemorrhage, immune challenge, noise, restraint and forced swim. All stressors elicited c‐fos expression in 25–30% of hypothalamic paraventricular nucleus corticotrophin‐releasing‐factor cells, suggesting that these stimuli were of comparable strength, at least with regard to their ability to activate the hypothalamic–pituitary–adrenal axis. In the amygdala, haemorrhage and immune challenge both elicited c‐fos expression in a large number of neurons in the central nucleus of the amygdala, whereas noise, restraint and forced swim primarily elicited recruitment of cells within the medial nucleus of the amygdala. In the medulla, all stressors recruited similar numbers of noradrenergic (A1 and A2) and adrenergic (C1 and C2) cells. However, haemorrhage and immune challenge elicited c‐fos expression in subpopulations of A1 and A2 noradrenergic cells that were significantly more rostral than those recruited by noise, restraint or forced swim. The present data support the suggestion that the brain recognizes at least two major categories of stressor, which we have referred to as ‘physical’ and ‘psychological’. Moreover, the present data suggest that the neural activation footprint that is left in the brain by stressors can be used to determine the category to which they have been assigned by the brain.
Projections from the superior temporal sulcus to the agranular frontal cortex in the macaque
Authors: Luppino Giuseppe , Calzavara Roberta , Rozzi Stefano , Matelli Massimo
Published: March 2003

The aim of this study was to investigate the organization of the projections from the superior temporal sulcus (STS) to the various areas forming the agranular frontal cortex. Injections of retrograde neuronal tracers were made in the various agranular areas, in nine macaque monkeys. The results showed that two rostral premotor areas, F6 (pre‐SMA) and F7, and the ventrorostral part of area F2 (F2vr) are targets of projections from the upper bank of the STS (uSTS). F6 and the dorsorostral part of F7 (supplementary eye field, SEF) are targets of projections from the rostral part of the uSTS, corresponding to the so‐called ‘superior temporal polysensory area’ (STP). In contrast, the ventral part of area F7 (not including the SEF) and F2vr are targets of afferents from the caudal part of the uSTS. Ventral F7 is the target of weak afferents from the caudalmost and dorsalmost part of the uSTS (area 7a), whilst F2vr is the target of projections from a relatively more rostral and ventral sector of the uSTS, close to the fundus of the sulcus. This sector should correspond to area MST. In conclusion, F6 and SEF receive high order information from STP, whereas ventral F7 and F2vr receive information from areas of the dorsal visual stream.
The nitric oxide system modulates the in vivo release of acetylcholine in the nucleus accumbens induced by stimulation of the hippocampal fornix/fimbria‐projection
Authors: Kraus Michaela M. , Prast Helmut
Published: March 2003

Nerve signals from the hippocampus to the nucleus accumbens (NAc) are transmitted through a glutamatergic pathway via the fornix/fimbria fibres. The aim of the present study was to investigate whether cholinergic neurons are activated by this projection and whether the nitric oxide (NO) system is also involved in the signal transduction within this nucleus. For this purpose, the NAc of urethane‐anaesthetized rats was superfused, by the push‐pull technique, with compounds that influence the NO system while the fornix/fimbria was electrically stimulated for short periods. The amount of acetylcholine (ACh) released in the superfusate was then determined. Electrical stimulation of the fornix/fimbria increased the ACh output in the NAc. This effect was abolished by superfusion with tetrodotoxin and decreased by superfusion with the glutamate receptor antagonists AP‐5 and DNQX indicating the involvement of action potentials and glutamate. Superfusion with the inhibitor of neuronal NO synthase, NS 2028 also diminished stimulation‐evoked ACh release. The NO donor PAPA/NO increased basal release. Simultaneous application of PAPA/NO and electrical stimulation led to an over‐additive increase of ACh release. The effect of PAPA/NO on stimulation‐evoked release was also abolished by NS 2028. The selective inhibitor of phosphodiesterase type 5 (PDE 5), 5‐[2‐ethoxy‐5‐(morpholinylacetyl)phenyl]‐1,6‐dihydro‐1‐methyl‐3‐propyl‐7H‐pyrazolo[4,3‐d]pyrimidin‐7‐one methanesulphanate monohydrate also enhanced stimulation‐induced release of ACh. Our findings indicate, that action potentials propagated by the fornix/fimbria to the NAc release glutamate which increases ACh release predominantly via NMDA receptors. In addition, nitrergic neurons are activated to enhance NO synthesis. The released NO seems to exert, via cGMP, a potent facilitatory role in the transduction and processing of signals from the hippocampus within the NAc, while the PDE 5 decreases the effects of NO.
Capsaicin‐evoked CGRP release from rat buccal mucosa: development of a model system for studying trigeminal mechanisms of neurogenic inflammation
Authors: Flores Christopher M. , Leong Anthony S. , O. Dussor Gregory ,   Catherine Harding‐Rose,, Hargreaves Kenneth M. , Kilo Sonja
Published: March 2003

Many of the physiological hallmarks associated with neurogenic inflammatory processes in cutaneous tissues are similarly present within orofacial structures. Such attributes include the dependence upon capsaicin‐sensitive sensory neurons and the involvement of certain inflammatory mediators derived therein, including calcitonin gene‐related peptide (CGRP). However, there are also important differences between the trigeminal and spinal nervous systems, and the potential contributions of neurogenic processes to inflammatory disease within the trigeminal system have yet to be fully elucidated. We present here a model system that affords the ability to study mechanisms regulating the efferent functions of peptidergic terminals that may subserve neurogenic inflammation within the oral cavity. Freshly dissected buccal mucosa tissue from adult, male, Sprague–Dawley rats was placed into chambers and superfused with oxygenated, Krebs buffer. Serial aliquots of the egressing superfusate were acquired and analysed by radioimmunoassay for immunoreactive CGRP (iCGRP). Addition of the selective excitotoxin, capsaicin (10–300 µm), to the superfusion buffer resulted in a significant, concentration‐dependent increase in superfusate levels of iCGRP. Similarly, release of iCGRP from the buccal mucosa could also be evoked by a depolarizing concentration of potassium chloride (50 mm) or by the calcium ionophore A23187 (1 µm). The specific, capsaicin receptor antagonist, capsazepine (300 µm), completely abolished the capsaicin‐evoked release of iCGRP while having no effect whatsoever on the potassium‐evoked release. Moreover, capsaicin‐evoked release was dependent upon the presence of extracellular calcium ions and was significantly, though incompletely, attenuated by neonatal capsaicin denervation. Collectively, these data indicate that the evoked neurosecretion of iCGRP in response to capsaicin occurs via a vanilloid receptor‐mediated, exocytotic mechanism. The model system described here should greatly facilitate future investigations designed to identify and characterize the stimuli that regulate the release of CGRP or other neurosecretory substances in isolated tissues. This system may also be used to elucidate the role of these mediators in the aetiology of inflammatory processes within the trigeminal field of innervation.