bluuebunny/crossref_metadata_2025 huggingface dataset:
Schwann cells genetically modified to secrete human BDNF promote enhanced axonal regrowth across transected adult rat spinal cord
Authors: Menei Philippe , Montero‐Menei Claudia , Whittemore Scott R. , Bunge Richard P. , Bunge Mary Bartlett
Published: March 2003

The infusion of BDNF and NT‐3 into Schwann cell (SC) grafts promotes regeneration of brainstem neurones into the grafts placed in adult rat spinal cord transected at T8 (Xuet al. 1995b). Here, we compared normal SCs with SCs genetically modified to secrete human BDNF, grafted as trails 5 mm long in the cord distal to a transection site and also deposited in the transection site, for their ability to stimulate supraspinal axonal regeneration beyond the injury. SCs were infected with the replication‐deficient retroviral vector pL(hBDNF)RNL encoding the human preproBDNF cDNA. The amounts of BDNF secreted (as detected by ELISA) were 23 and 5 ng/24 h per 106cells for infected and normal SCs, respectively. Biological activity of the secreted BDNF was confirmed by retinal ganglion cell bioassay. The adult rat spinal cord was transected at T8. The use of Hoechst prelabelled SCs demonstrated that trails were maintained for a month. In controls, no SCs were grafted. One month after grafting, axons were present in SC trails. More 5‐HT‐positive and some DβH‐positive fibres were observed in the infected vs. normal SC trails. When Fast Blue was injected 5 mm below the transection site (at the end of the trail), as many as 135 retrogradely labelled neurones could be found in the brainstem, mostly in the reticular and raphe nuclei (normal SCs, up to 22, mostly in vestibular nuclei). Numerous neurones were labelled in the ventral hypothalamus (normal SCs, 0). Also, following Fast Blue injection, a mean of 138 labelled cells was present in dorsal root ganglia (normal SCs, 46) and spinal cord (39 vs. 32) rostral to the transection. No labelled spinal neurones rostral to the transection were seen when SCs were not transplanted. Thus, the transplantation of SCs secreting increased amounts of BDNF improved the regenerative response across a transection site in the thoracic cord. Moreover, the enhanced regeneration observed with infected SCs may be specific as the largest response was from neurones known to expresstrkB.
Responses of human primary sensorimotor and supplementary motor areas to internally triggered unilateral and simultaneous bilateral one‐digit movements. A high‐resolution EEG study
Authors: Urbano A. , Babiloni C. , Onorati P. , Carducci F. , Ambrosini A. , Fattorini L. , Babiloni F.
Published: March 2003

We modelled the responses of human primary sensorimotor areas and supplementary motor area to simple, self‐initiated unilateral and simultaneous bilateral middle finger movements using a novel high‐resolution electroencephalography technology. The results support the view that these cortical motor areas are involved in parallel and present similar activity in the preparation, initiation, and execution of the contralateral and bilateral movements. Furthermore, the left primary sensorimotor area (dominant hemisphere) appears to be activated more than the right primary sensorimotor area during the preparation and performance of the ipsilateral movements.
A caspase inhibitor blocks ischaemia‐induced delayed neuronal death in the gerbil
Authors: Himi Toshiyuki , Ishizaki Yasuki , Murota Sei‐itsu
Published: March 2003

Caspases play a critical role in the cell death machinery in various cell types. Here we investigated the involvement of caspases in the delayed neuronal death after transient global forebrain ischaemia in the gerbil. Intrahippocampal injection of benzyloxycarbonyl‐Asp‐CH2‐dichlorobenzene (zD), an irreversible inhibitor of caspases, saved hippocampal CA1 neurones from chromatin condensation and DNA fragmentation at post‐ischaemia day 4, and these neurones maintained normal morphology at day 8 post‐insult. Intrahippocampal injection of interleukin‐1β (IL‐1β) after ischaemic insults did not influence the neuroprotective effect of zD, suggesting that the neuroprotective effect does not depend on the inhibition of mature IL‐1β production. Animals that received zD‐injection showed significant improvement in step‐through and step‐down passive avoidance learning at post‐ischaemia days 4 and 5, suggesting that neural functions were preserved in these animals. At post‐ischaemia day 4, the cleavage of poly(ADP‐ribose)polymerase was observed, and this cleavage was almost completely suppressed in zD‐injected hippocampus, suggesting involvement of caspase‐3 and caspase‐3‐like caspase in the delayed neuronal death. Our findings indicate that caspases play important roles in the delayed neuronal death after transient global forebrain ischaemia in the gerbil, and suggest that ischaemia‐induced brain damage can be blocked by caspase inhibitors.
Comparing the effects of selective cingulate cortex lesions and cingulum bundle lesions on water maze performance by rats
Authors: Warburton E.C. , Aggleton J.P. , Muir J.L.
Published: March 2003

The ability of rats to learn the location of a hidden platform in a swim maze was compared in animals with excitotoxic lesions of the anterior or posterior (retrosplenial) cingulate cortex or radiofrequency lesions of the cingulum bundle or fimbria‐fornix. Performance of this allocentric spatial task was unaffected by the posterior cingulate cortex lesions, while anterior cingulate cortex damage produced only a mild acquisition deficit. Transection of the fornix and lesions of the cingulum bundle produced similar patterns of impairment on initial acquisition, but the cingulum bundle lesions had less effect on reversal of the task. The results from the water maze, and from a subsequent T‐maze alternation task, indicate that cingulum bundle lesions can produce a spatial deficit that is similar, but milder, to that observed after fornix transection. The results of the excitotoxic lesions suggest that previous studies examining conventional cingulate lesions may have been influenced by damage to adjacent fibre tracts, such as the cingulum bundle.
Dexterity in adult monkeys following early lesion of the motor cortical hand area: the role of cortex adjacent to the lesion
Authors: Rouiller E.M. , Yu X.H. , Moret V. , Tempini A. , Wiesendanger M. , Liang F.
Published: March 2003

Infant monkeys were subjected to unilateral lesions of the motor cortex (mainly its hand representation). After maturation, they showed normal use of the contralateral hand for global grip movements. However, as compared with the ipsilateral hand, precision grip tasks requiring relatively independent finger movements were performed with less dexterity, particularly if adjustments of the wrist position were necessary. The purpose of this study was to investigate mechanisms which may be responsible for the rather well, although not complete, preservation of manipulative behaviour of these adult monkeys. To this end, the hand representations were mapped bilaterally with intracortical microstimulation in the mature monkeys, and the dexterity of both hands assessed quantitatively in a precision grip task. The behavioural effects of reversible inactivations of the primary (M1) and supplementary (SMA) motor cortical areas were then tested. The following were found. (i) The hand contralateral to the lesion exhibited subtle but significant dexterity deficits, as compared with the ipsilateral hand; the deficit was essentially for complex movements requiring dissociation of the thumb–index finger pinch from the other digits, involving also an arm rotation. (ii) Reversible inactivation of the M1 hand representation in the intact hemisphere dramatically impaired dexterity of the opposite hand without affecting the ipsilateral hand (contralateral to the early lesion). (iii) A relatively complete hand representation was found to occupy a new territory, medial to the old lesion. (iv) The role of this new displaced representation was crucial for the preserved dexterity of the opposite hand, as evidenced by its functional inactivation. In contrast, inactivation of both SMA cortices did not interfere with the manipulative behaviour. It is thus concluded that the preserved functional capacity of manipulations with the hand opposite the early lesion can be essentially attributed to a cortical reorganization around the old lesion. Under the present experimental conditions, contributions from either the SMA or the intact M1 appear not to be crucial.
Deafferentation up‐regulates the expression of the mGlu1a metabotropic glutamate receptor protein in the olfactory bulb
Authors: Casabona G. , Catania M.V. , Storto M. , Ferraris N. , Perroteau I. , Fasolo A. , Nicoletti F. , Bovolin P.
Published: March 2003

Chemical lesion of olfactory neuroepitheium induced an up‐regulation of the mGlu1a metabotropic glutamate receptor protein in the olfactory bulb, as shown by Western blot analysis. At 2 days after the lesion, the increase in the receptor protein was associated with an increase in mGlu1a mRNA levels; in contrast, at longer times after the lesion (16 days), mRNA levels were reduced in spite of the high expression of the receptor protein, perhaps as a result of product‐inhibition of mGlu1 gene expression. Immunohistochemical analysis showed that the increase in mGlu1a induced by olfactory denervation was confined to the glomeruli, which occupy the external portion of the olfactory bulb. Within these structures, mGlu1a receptors are mainly localized on the distal dendrites of mitral cells, which are innervated by the glutamatergic axons of the olfactory nerve.

These results demonstrate that the expression of mGlu1a receptors is up‐regulated in response to glutamatergic deafferentation, supporting a role for this particular receptor subtype in the physiology of synaptic transmission.
Behavioural effects of subthalamic nucleus lesions in the hemiparkinsonian marmoset (Callithrix jacchus)
Authors: Henderson J.M. , Annett L.E. , Torres E.M. , Dunnett S.B.
Published: March 2003

Recent studies in non‐human primates support a role for the subthalamic nucleus in the expression of parkinsonian symptomatology, and it has been proposed that subthalamic lesions may provide a surgical treatment for the symptoms of Parkinson’s disease in humans. We have applied a broad range of behavioural tests to characterize the effects of lesions of the subthalamic nucleus on parkinsonian symptoms in the unilateral 6‐hydroxydopamine (6‐OHDA) lesioned marmoset (Callithrix jacchus). Thirteen marmosets were trained on a battery of behavioural tasks that were conducted at regular intervals before and after surgery. All received unilateral 6‐OHDA lesions to the medial forebrain bundle. Seven animals were then given an additional N‐methyl‐d‐aspartate lesion of the ipsilateral subthalamic nucleus, whereas the remaining six animals received a variety of control or sham lesions to the nucleus. The 6‐OHDA lesions induced a strong ipsilateral bias in head position; mild–moderate ipsilateral rotation spontaneously and after injection of saline or amphetamine; and contralateral rotation after injection of apomorphine. Hemineglect was evident as delayed initiation of reaches on the contralateral side on the staircase reaching task. Additional subthalamic lesions significantly reversed the bias in head position from ipsilateral to contralateral and decreased neglect as evidenced by improved latencies to initiate reaching on the contralateral side at the staircase. However, deficits in skilled movements persisted in the subthalamic nucleus lesion group in that they did not complete the staircase task any faster than the control group and remained impaired on another task which required reaching into tubes. These behavioural effects demonstrate that excitotoxic lesioning of the subthalamic nucleus can ameliorate some, but not all, parkinsonian‐like deficits in the unilateral 6‐OHDA lesioned marmoset.
Focal ischaemia of the rat brain elicits an unusual inflammatory response: early appearance of CD8+ macrophages/microglia
Authors: Jander Sebastian , Schroeter Michael , D’Urso Donatella , Gillen Clemens , Witte Otto W. , Stoll Guido
Published: March 2003

Cerebral ischaemia leads to profound glial activation and leukocyte infiltration into the infarct area. In this study, we provide evidence for a dual macrophage response in focal ischaemic lesions of the rat brain. We show that a considerable proportion of macrophages in the ischaemic lesions express the CD8αβ heterodimer to date only described on CD8+ T cells. As known from other lesion paradigms, CD4+ macrophages were also present. Interestingly, CD8‐ and CD4‐expressing macrophages formed two non‐overlapping subpopulations. CD8+ macrophages reached their maximum during the first week with pronounced downregulation thereafter whereas CD4+ cells persisted at high levels into the second week. In contrast to cerebral ischaemia, macrophages in the spleen and in Wallerian degeneration after optic nerve axotomy expressed CD4, but not CD8. In experimental autoimmune encephalomyelitis, CD8 was mainly associated with T cells and very weakly detectable on some ramified cells resembling activated microglia. In conclusion, we show that cerebral ischaemia triggers an unusual inflammatory response characterized by the appearance of CD8+/CD4– macrophages that might exert specific functions in the pathogenesis of ischaemic brain damage.
Cytokines promote the survival of mouse cranial sensory neurones at different developmental stages
Authors: Horton Antony R. , Bartlett Perry F. , Pennica Diane , Davies Alun M.
Published: March 2003

To investigate when the neurotrophic cytokines ciliary neurotrophic factor (CNTF), leukaemia inhibitory factor (LIF), oncostatin‐M (OSM), interleukin‐6 (IL‐6) and cardiotrophin‐1 (CT‐1) act on developing sensory neurones and whether they co‐operate with neurotrophins in regulating neuronal survival, we studied the in vitro trophic effects of these factors on two well‐characterized populations of cranial sensory neurones at closely staged intervals throughout embryonic development. The cutaneous sensory neurones of the trigeminal ganglion, which show an early, transient survival response to BDNF and NT3 before becoming NGF‐dependent, were supported by CNTF, LIF, OSM and CT‐1 during the late fetal period, several days after the neurones become NGF‐dependent. At this stage of development, these cytokines promoted the survival of a subset of NGF‐responsive neurones. The enteroceptive neurones of the nodose ganglion, which retain dependence on BDNF throughout fetal development, were supported throughout their development by CNTF, LIF, OSM and CT‐1, and displayed an additional survival response to IL‐6 in the late fetal period. These findings indicate that populations of sensory neurones display different developmental patterns of cytokine responsiveness and show that embryonic trigeminal neurones pass through several phases of differing neurotrophic factor survival requirements.
Kinetics of AMPA‐type glutamate receptor channels in rat caudate‐putamen neurones show a wide range of desensitization but distinct recovery characteristics
Authors: Jahn K. , Bufler J. , Franke C.
Published: March 2003

α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA)‐type glutamate receptor channels of rat caudate‐putamen neurones were studied by ultrafast application of agonists to outside‐out vesicles taken from medium‐sized spiny neurones in thin slices. Upon application of 10 m m glutamate for 50 ms, fast rising and desensitizing currents were activated. Ten to 90% rise time values were ≈ 0.5 ms. Dose–response studies revealed an EC50 of 0.63 m
m glutamate. In double logarithmic coordinates, the curve had a maximal slope between 1.33 and 1.85 at low concentrations, indicating at least two binding sites for glutamate. Rise time increased with low agonist concentrations, whereas desensitization kinetics showed only a weak dependence on concentration. The time constant of desensitization was fitted with one exponential and ranged between 2 and 11 ms, with a mean of 6.19 ± 2.31 ms (n = 239). Following brief glutamate pulses (1 ms) currents decayed with time constants of 2.7 ± 0.23 ms (n = 12). Recovery from desensitization was investigated by double‐pulse experiments. Recovery time constants fell in two subgroups with respective mean values of 110.6 ± 14.2 ms (n = 8) and 288.6 ± 33.2 ms (n = 8). By adding low glutamate concentrations to the bath solution, predesensitization of AMPA‐type receptors without channel opening could be shown. A 50% reduction in control amplitude was achieved with 5.2 ± 2.1 μm (n = 22) glutamate in the background. We hypothesize a circular reaction scheme with at least two binding sites for glutamate to describe activation, desensitization and recovery from desensitization in rat caudate‐putamen neurones.
N‐Syndecan and HB‐GAM (Heparin‐Binding Growth‐Associated Molecule) associate with early axonal tracts in the rat brain
Authors: Kinnunen Anu , Kinnunen Tarja , Kaksonen Marko , Nolo Riitta , Panula Pertti , Rauvala Heikki
Published: March 2003

Heparin‐Binding Growth‐Associated Molecule (HB‐GAM)/pleiotrophin is an 18 kDa extracellular matrix‐ and cell‐surface‐associated protein shown to enhance neurite outgrowth of perinatal forebrain neurones in vitro. The heparan sulphate proteoglycan N‐syndecan (
Raulo et al. 1994
) has been isolated as a receptor/coreceptor for the HB‐GAM. We have investigated, whether HB‐GAM and N‐syndecan could have a similar role in neurite outgrowth and axon guidance in early axonal tracts of brain. In the present study N‐syndecan was found to be spatiotemporally associated with the developing axonal tracts already on embryonic day 9 in rat, as revealed by coexpression with class III β‐tubulin, which is one of the earliest neuronal markers (
Easter et al. 1993
;Brittis et al. 1995
). Later, N‐syndecan and HB‐GAM were detected in the first afferent serotonergic projections arising from the pontine raphe nuclei. The expression pattern of HB‐GAM peaked in the developing rhombencephalon at embryonic stage (E) 13–14. At the same time, N‐syndecan was expressed in the developing raphe neurones growing neurites towards the diencephalon along HB‐GAM immunoreactive pathways. When rhombencephalic neurones were cultured on decreasing concentrations of substrate‐bound HB‐GAM, E13 neurones showed a significantly better neurite outgrowth response than E11, E16 or E18 neurones. The neurite outgrowth of raphe neurones in vitro was inhibited by adding soluble heparin or N‐syndecan into the culture medium, whereas addition of chondroitin sulphate had no effect. In a simple pathway assay, E13 raphe neurones selectively preferred attaching and growing neurites on pathways containing HB‐GAM as compared with regions containing either laminin or fibronectin alone. Our results suggest that HB‐GAM may function as a developmentally regulated cue for rhombencephalic neurones that possess N‐syndecan on their cell membrane.
Long‐lasting increased pain sensitivity in rat following exposure to heroin for the first time
Authors: Laulin Jean‐Paul , Larcher Agnès , Célèrier Evelyne , Moal Michel Le , Simonnet Guy
Published: March 2003

Acute dependence, defined as a precipitation of somatic signs by an antagonist, may occur after a single administration of an opiate drug. Because hyperalgesia is a consistent sign of the withdrawal syndrome, we tested the effectiveness of heroin, an opiate used by addicts, to induce pain facilitation even after a first exposure to the drug. In opiate‐naive rats, subcutaneous injection of heroin induced analgesia followed by allodynia, a decrease in pain threshold. This latter phenomenon was observed in the absence of noxious stimuli and lasted several days. An N‐methyl‐d‐aspartate (NMDA) receptor antagonist, MK‐801 prevented such long‐lasting allodynia. These results suggest that allodynia is an early sign reflecting neural plasticity associated with the development of dependence.
The cerebral metabolic effects of manipulating glutamatergic systems within the basal forebrain in conscious rats
Authors: Browne Susan E. , Muir Janice L. , Robbins Trevor W. , Page Keith J. , Everitt Barry J. , McCulloch James
Published: March 2003

N‐methyl‐d‐aspartate (NMDA) and non‐NMDA receptor‐mediated manipulations of the cortical cholinergic input arising from the basal forebrain differentially affect cognitive function. We used [14C]‐2‐deoxyglucose autoradiography in conscious rats to map the effects of excitatory amino acid agonist infusions into the nucleus basalis magnocellularis (NBM) on cerebral functional activity, as reflected by local rates of glucose utilization. Acute stimulation of NBM neurones by local infusion of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA), 15 min before glucose use measurement, resulted in glucose use reductions in nine cortical regions innervated by NBM efferents including prefrontal, frontal, sensorimotor and cingulate cortices. NMDA infusions altered glucose use in two cortical areas. Both AMPA and NMDA markedly increased glucose use in the striatum and globus pallidus, with concomitant perturbations in striato‐pallidal projection targets including the substantia nigra, entopeduncular nucleus, subthalamic nucleus and lateral habenular nucleus. In contrast, the GABAA agonist muscimol did not affect glucose use in the NBM or neocortical regions, but induced glucose use increases in several subcortical nuclei including the substantia nigra and entopeduncular nucleus.

The delayed effects of excitotoxic lesions were assessed 3 weeks after basal forebrain infusions of AMPA, NMDA, ibotenate or quisqualate. Statistically significant glucose use changes only occurred in the hypothalamus after NMDA, and the NBM after ibotenate infusions, although reduced cortical metabolism was apparent following AMPA‐induced lesions of the NBM. Results support a dissociation between the functional sequelae of NMDA and non‐NMDA receptor‐mediated events in the basal forebrain, and long‐term compensatory functional adaptation following cortical denervation.
Pattern formation in the cerebellum of murine embryonic stem cell chimeras
Authors: Hawkes Richard , Faulkner‐Jones Beverly , Tam Patrick , Tan Seong‐Seng
Published: March 2003

The cerebellar cortex is subdivided into an elaborate, stereotyped array of transverse zones and parasagittal stripes. It has been speculated that (i) all Purkinje cells derive from 10 to 20 precursors allocated early in embryogenesis and (ii) that pattern formation is based on cell lineage restriction in the founder pool. These hypotheses have been tested by clonal analysis of embryonic stem cell chimeras. Neither speculation is supported: the analysis suggests that Purkinje cells derive from a founder population of > 102 precursors, and that neither cerebellar transverse developmental boundaries nor parasagittal stripes have a clonal origin. We conclude that early lineage restriction plays no role in cerebellar pattern formation.
Functional magnetic resonance imaging of a human auditory cortex area involved in foreground–background decomposition
Authors: Scheich Henning , Baumgart Frank , Gaschler‐Markefski Birgit , Tegeler Carola , Tempelmann Claus , Heinze Hans J. , Schindler Frank , Stiller Detlef
Published: March 2003

Auditory foreground–background decomposition is a pattern recognition process which combines simultaneous and sequential grouping in complex sound sequences. Using functional magnetic resonance imaging with reduced scanner noise and stimulation through a new type of earphones, we investigated the possibility that this process activates topographically distinct areas of human auditory cortex. A basic matching‐to‐sample task with variable tones (sequential grouping) caused significant activity in three separate landmark‐related territories on the supratemporal plane. A similar task in the presence of a strongly masking acoustic background pattern to challenge simultaneous grouping led to the distinction of the subterritory in which foreground signal‐related or task‐related signal properties were exclusively seen. In contrast to the remainder of territories the level of activity and the periodicity of the signal time‐course was resistant to the masking influence of the background.

This suggests that auditory foreground–background decomposition involves a specialized non‐primary auditory cortex field. Generally, the findings demonstrate functional parcellation of auditory cortex for which the evidence in humans, in contrast to other primates, is only indirect to date.
Characterization of perforant path lesions in rodent models of memory and attention
Authors: Kirkby D.L. , Higgins G.A.
Published: March 2003

Early stage Alzheimer's disease (AD) pathology is associated with neurodegeneration of systems within the temporal cortex, e.g. the entorhinal cortex, perforant pathway and hippocampus. The perforant pathway provides the major neuronal input to the hippocampus from the entorhinal cortex and thus relays multimodal sensory information derived from cortical zones into the hippocampus. The earliest symptoms of AD include cognitive impairments, e.g. deficits in short‐term memory and attention. Consequently, we have investigated the effect of bilateral knife cut lesions to the perforant path on cognition in rats using models measuring primarily short‐term memory (operant delayed match to position task), attention (serial five‐choice reaction time task) and spatial learning (Morris water maze). Rats receiving bilateral perforant path lesions showed normal neurological function and a mild hyperactivity. The lesion produced little effect on attention assessed using the five‐choice task. In contrast, animals with equivalent lesions showed a robust delay‐dependent deficit in the delayed match to position task. Spatial learning in the water maze task was also severely impaired. The delay‐dependent deficit in the match to position task was not reversed by tacrine (3 mg/kg) pretreatment. The present data support a selective impairment of cognitive function following perforant path lesions that was confined to mnemonic rather than attentional processing. These findings complement primate and human studies identifying a critical role of the perforant pathway and associated temporal lobe structures in declarative memory. Degeneration of the perforant pathway is likely to contribute to the mnemonic deficits characteristic of early AD. The failure of tacrine to ameliorate these deficits may be relevant to an emerging clinical literature suggesting that cholinomimetic therapies improve attentional rather than mnemonic function in AD.
Localization of a G protein Gi2 in the cilia of rat ependyma, oviduct and trachea
Authors: Shinohara Haruo , Asano Tomiko , Kato Kanefusa , Kameshima Takamichi , Semba Reiji
Published: March 2003

In previous studies, the localization of a pertussis toxin‐sensitive G protein was demonstrated in ependymal cilia, but the identification of the subtype of G protein was inconsistent. To clarify this issue, we studied the localization of Goα, Gi1α, Gi3α and Gi2α in the ciliated ependymal cells and in the cilia of some other tissues of rats using specific antibodies. The cilia of the ependymal cells that line the ventricular cavity of the brain were intensely immunoreactive for Gi2α, but not for Goα, Gi1α or Gi3α. Immunoblot analysis demonstrated higher levels of Gi2α in the ependymal cilia‐rich pellet than in the motor area of the parietal cortex. At the ultrastructural level, the immunoreactivity specific for Gi2α was found predominantly in the cilia, but rarely in the microvilli or the basal bodies of ependymal cells. In cross‐sections, the immunoreactivity specific for Gi2α was observed only in cell membranes, in particular, in the inner electron‐dense leaflet of the trilaminar structure. In addition to that in the ependymal cilia, such specific localization of Gi2α was observed in the motile cilia in other tissues, including the oviduct and trachea. By contrast, the stereocilia in the ductus deferens were not immunopositive for Gi2α. These findings suggest that Gi2 might play an important role in the signal transduction in ciliary membrane‐associated function(s) of the ependymal cells, oviduct and trachea.
Increased flexibility and selectivity in spatial learning of transgenic mice ectopically expressing the neural cell adhesion molecule L1 in astrocytes
Authors: Wolfer David P. , Mohajeri Hasan M. , Lipp Hans‐Peter , Schachner Melitta
Published: March 2003

The expression of the neural cell adhesion molecule L1 is altered by neuronal activity and promotes neurite outgrowth in vitro. To study the effects of L1 on learning and synaptic plasticity, transgenic mice have been created which express L1 ectopically in glial fibrillary acidic protein (GFAP) expressing astrocytes. Ninety mice, including GFAP‐L1‐transgenic mice from two genetic backgrounds and their littermates, were tested for swimming navigation learning in the Morris water maze according to a standardized protocol. While learning the position of an invisible target platform and also relearning its position after relocation, GFAP‐L1‐transgenic mice spent a greater fraction of their swim time in the target quadrant. Moreover, they showed a more rapid improvement of escape performance during the first day of training. Factor analysis revealed that this difference in swimming pattern could not be explained by non‐cognitive factors. Factor analysis also revealed that, during a probe trial, the GFAP‐L1‐transgenic mice spent comparatively less time in the old target quadrant than predicted by the increased searching they had shown during acquisition learning. Hence, ectopic expression of L1 by astrocytes in mice appears to be linked to a factor which increases behavioural flexibility and selectivity while learning and relearning, but concomitantly may lead to a relative reduction of spatial retention.
Seizure prediction by non‐linear time series analysis of brain electrical activity
Authors: Elger Christian E. , Lehnertz Klaus
Published: March 2003

Brain electrical activity of 16 patients with temporal lobe epilepsy, recorded intracranially during seizure‐free intervals as well as during transitions to the seizure state, was analysed using methods derived from the theory of non‐linear dynamics. Long‐lasting and marked changes towards low‐dimensional system states were found to occur specifically up to 25 min prior to epileptic seizures and allow to predict the occurrence of individual seizures in time. These findings reflect a continuous increase in the degree of synchronicity, and thus open a window for the study of mechanisms generating seizures in humans. This offers new possibilities for therapeutic interventions.
Polarized sorting of nicotinic acetylcholine receptors to the postsynaptic membrane in Torpedo electrocyte
Authors: Camus Gilles , Jasmin Bernard J. , Cartaud Jean
Published: March 2003

Several regulatory mechanisms contribute to the accumulation and maintenance of high concentrations of acetylcholine receptors (AChR) at the postsynaptic membrane of the neuromuscular junction, including compartmentalized gene transcription, targeting, clustering and anchoring to the cytoskeleton. The targeting of the AChR to the postsynaptic membrane is likely to involve a polarized sorting in the exocytic pathway. In this work, we used the electrocyte of Torpedo marmorata electric organ to study the intracellular trafficking of neosynthesized AChR and its delivery to the postsynaptic membrane. Gradient centrifugation and immunoisolation techniques have led to the isolation of two populations of post‐Golgi transport vesicles (PGVs) enriched in proteins of either the innervated (AChR) or non‐innervated (Na,K‐ATPase) membrane domains of the cell. Immunolabelling of these vesicles at the EM level disclosed that very few PGVs contained both proteins. In AChR‐enriched vesicles, high sialylation of AchR molecules, an expected post‐translational modification of proteins exiting the trans‐Golgi network, and the presence of a marker of the exocytic pathway (Rab6p), indicate that these vesicles are carriers engaged in the Golgi‐to‐plasma membrane transport. These data suggest that AChR and Na,K‐ATPase are sorted intracellularly most likely within the trans‐Golgi network. Furthermore, EM analysis and immunogold‐labelling experiments provided in situ evidence that the AChR‐containing PGVs are conveyed to the postsynaptic membrane, possibly by a microtubule‐dependent transport mechanism. Our data therefore provide the first evidence that the targeting of receptors for neurotransmitters to synaptic sites could be contributed by intracellular sorting and polarized delivery in the exocytic pathway.
Mechanisms and functional significance of a slow inhibitory potential in neurons of the lateral amygdala
Authors: Danober Laurence , Pape Hans‐Christian
Published: March 2003

A slow inhibitory potential (sIP) elicited upon synaptic activation in spiny, pyramidal‐like cells with properties indicative of projection neurons was investigated in slices of the rat and guinea‐pig lateral amygdala in vitro. The sIP succeeded the triphasic sequence of excitatory and fast/slow inhibitory postsynaptic potentials mediated via glutamate and GABAA/B receptors, respectively, was readily evoked upon repetitive stimulation of the external capsule and appeared to terminate epileptiform burst discharges during pharmacologically reduced GABAergic influence. The sIP reversed close to the Cl– equilibrium potential, but was not affected by altered transmembrane Cl– gradients and not abolished by antagonists to ligand‐gated Cl– channels. Intracellular injection of QX 314 and resulting blockade of sodium spikes had no effect, whereas the Ca2+ chelator BAPTA blocked the sIP concomitantly with slow hyperpolarizing afterpotentials following intrinsically generated spike firing, thereby indicating the contribution of Ca2+‐dependent mechanisms secondary to synaptic activation. During action of BAPTA and QX 314, an N‐methyl‐d‐aspartate (NMDA) receptor‐mediated potential was unmasked, which contributed to the sIP. The Ca2+‐dependent mechanisms of the sIP involved a membrane K+ conductance, as was indicated by the dependence on the K+ gradient and the shift of the reversal potential towards the K+ equilibrium potential during blocked NMDA receptors. During the presence of GABA receptor antagonists, reduction of the Ca2+‐activated K+ conductance through injection of BAPTA or application of dopamine induced a gradual shift of interictal‐like single bursts of spikes towards the generation of re‐occurring ictal‐like activity. It is concluded that pyramidal‐like projection cells in the AL can generate a sIP upon synaptic activation, which reflects the combined activation of an NMDA receptor‐mediated cation current and a K+ current that is secondary to the rise in intracellular Ca2+ concentration resulting from the preceding depolarizing response. The sIP may play an important role in controlling excitatory activity in the amygdala, particularly in preventing the transformation of interictal‐like activity towards recurrent epileptic discharges during periods of decreased GABAergic influence.
Tumour necrosis factor‐α and interleukin‐2 differentially affect hippocampal serotonergic neurotransmission, behavioural activity, body temperature and hypothalamic–pituitary–adrenocortical axis activity in the rat
Authors: Pauli Sabine , Linthorst Astrid C. E. , Reul Johannes M. H. M.
Published: March 2003

Intraperitoneal endotoxin injection and central administration of interleukin (IL)‐1β profoundly activate hippocampal serotonergic neurotransmission. This study was designed to investigate, using in vivo microdialysis, the effects of another endotoxin‐induced proinflammatory cytokine, tumour necrosis factor‐α, and the effects of the non‐inflammatory cytokine, IL‐2, on hippocampal extracellular levels of serotonin. To compare the effects of these cytokines on neurotransmission with the effects on physiological parameters and behaviour, hypothalamic–pituitary–adrenocortical (HPA) axis activity, body temperature and behavioural activity were monitored as well. Time‐dependent changes in serotonergic neurotransmission and HPA axis activity were determined by measuring serotonin, its metabolite 5‐hydroxyindoleacetic acid and free corticosterone in dialysates. Total behavioural activity was scored by assessing the time during which rats were active. Core body temperature was measured by biotelemetry. Intracerebroventricular injection of 50 or 100 ng recombinant murine tumour necrosis factor‐α exerted no effect on hippocampal serotonergic neurotransmission, and induced no signs of sickness behaviour. However, these doses produced a dose‐dependent increase in body temperature and free corticosterone levels. In contrast, intracerebroventricular administration of 500 ng, but not of 50 ng, recombinant human IL‐2 produced a marked increase in hippocampal extracellular concentrations of serotonin and 5‐hydroxyindoleacetic acid, accompanied by a pronounced behavioural inhibition and other signs of sickness. Moreover, both doses of IL‐2 caused a dose‐dependent increase in body temperature and free corticosterone levels. Interestingly, intracerebroventricular pretreatment with the IL‐1 receptor antagonist showed that the effects of IL‐2 on hippocampal serotonin were completely dependent on endogenous brain IL‐1. However, IL‐1 seemed to play only a minor role in the IL‐2‐induced increase in free corticosterone. Taken together, the results show that cytokines produce partially overlapping brain‐mediated responses, but are selectively effective in stimulating hippocampal serotonergic neurotransmission and inducing sickness behaviour. Moreover, we postulate that activation of hippocampal serotonin release is instrumental in the full development of behavioural inhibition.
Reciprocal modulation of TrkA and p75NTR affinity states is mediated by direct receptor interactions
Authors: Ross Gregory M. , Shamovsky Igor L. , Lawrance Gail , Solc Mark , Dostaler Suzanne M. , Weaver Donald F. , Riopelle Richard J.
Published: March 2003

Equilibrium binding of 125I‐nerve growth factor (125I‐NGF) to cells coexpressing the tyrosine kinase receptor A (TrkA) and common neurotrophin receptor (p75NTR), cells coexpressing both receptors where p75NTR is occupied, and cells expressing only p75NTR, revealed reciprocal modulation of receptor affinity states. Analysis of receptor affinity states in PC12 cells, PC12 cells in the presence of brain‐derived neurotrophic factor (BDNF), and PC12nnr5 cells suggested that liganded and unliganded p75NTR induce a higher affinity state within TrkA, while TrkA induces a lower affinity state within p75NTR. These data are consistent with receptor allosterism, and prompted a search for TrkA/p75NTR complexes in the absence of NGF. Chemical crosslinking studies revealed high molecular weight receptor complexes that specifically bound 125I‐NGF, and were immunoprecipitated by antibodies to both receptors. The heteroreceptor complex of TrkA and p75NTR alters conformation and/or dissociates in the presence of NGF, as indicated by the ability of low concentrations of NGF to prevent heteroreceptor crosslinking. These data suggest a new model of receptor interaction, whereby structural changes within a heteroreceptor complex are induced by ligand binding.
Characterization of a nicotinic acetylcholine receptor from the insect Manduca sexta
Authors: Eastham Helen M. , Lind Robert J. , Eastlake Jane L. , Clarke Barry S. , Towner Paul , Reynolds Stuart E. , Wolstenholme Adrian J. , Wonnacott Susan
Published: March 2003

Manduca sexta is a nicotine‐insensitive insect, the larval form of which feeds on tobacco. It has been postulated that its nicotine insensitivity may reflect the presence of a modified nicotinic acetylcholine receptor whose α subunits lack the amino acid residues necessary for binding nicotine: we have performed ligand binding assays and molecular cloning to examine this hypothesis. [125I]α‐Bungarotoxin bound specifically to both larval and adult membranes, with Kd values of 7.6 and 6.5 nm and Bmax values of 119 and 815 fmol/mg protein, respectively. The pharmacological profile of [125I]α‐bungarotoxin binding was similar in both tissues. In particular, nicotine (Ki values: 1.6 μm and 2 μm for larvae and adults, respectively) competed with an affinity similar to that found for nicotine‐sensitive insects. No α‐bungarotoxin‐insensitive binding sites labelled by [3H]epibatidine could be detected. Using the α‐like subunit from the locust Schistocerca gregaria to probe two cDNA libraries, and by inverse PCR on circularized genomic DNA from Manduca sexta, we have obtained overlapping cDNA clones that contain the complete coding sequence of a putative nicotinic subunit from Manduca sexta (MARA1). No other α‐subunit cDNAs were isolated using this probe, although it hybridized to multiple bands on Southern blots. The sequence of MARA1 is consistent with an α‐like subunit capable of binding α‐bungarotoxin, and it retains all those amino acids implicated in nicotine binding to vertebrate nicotinic receptors. Taken together, these findings provide no support for the hypothesis that the nicotine insensitivity of Manduca sexta is the result of a nicotinic receptor with diminished nicotine binding.
Gamma frequency oscillation in the hippocampus of the rat: intracellular analysis in vivo
Authors: Penttonen Markku , Kamondi Anita , Acsády László , Buzsáki György
Published: March 2003

Gamma frequency field oscillations reflect synchronized synaptic potentials in neuronal populations within the ≈ 10–40 ms range. The generation of gamma activity in the hippocampus was investigated by intracellular recording from principal cells and basket cells in urethane anaesthetized rats. The recorded neurones were verified by intracellular injection of biocytin. Gamma frequency field oscillations were nested within the slower theta waves. The phase and amplitude of intracellular gamma were voltage dependent with an almost complete phase reversal at Cl– equilibrium potential in pyramidal cells. Basket cells fired at gamma frequency and were phase‐locked to the same phase of the gamma oscillation as pyramidal cells. Current‐induced depolarization coupled with synaptically induced inhibition resulted in gamma frequency discharge (30–80 Hz) of pyramidal cells without accommodation. These observations suggest that at least part of the gamma frequency field oscillation reflects rhythmic hyperpolarization of principal cells, brought about by the rhythmically discharging basket neurones. Resonant properties of pyramidal cells might facilitate network synchrony in the gamma frequency range.
Origin of the synchronized network activity in the rabbit developing hippocampus
Authors: De La Prida L. Menendez , Bolea  , Sanchez‐Andres
Published: March 2003

Rhythmic spontaneous bursting is a fundamental hallmark of the immature hippocampal activity recorded in vitro. These bursts or giant depolarizing potentials (GDPs) are GABA‐ and glutamatergic‐driven events. The mechanisms of GDPs generation are still controversial, since although a hilar origin has been suggested, GDPs were also recorded from isolated CA3 area. Here, we have investigated the origin of GDPs in hippocampal slices from newborn rabbits. Simultaneous intracellular recordings were performed in CA3, CA1 and the fascia dentata. We found a high degree of correlation between the spontaneous GDPs present in CA3 and CA1 regions. Cross‐correlation analysis demonstrated that CA3 firing precedes CA1 by about 192 ms, although a significant population of discharges was recorded first in CA1 (20%). Granule cells (GCs) in the fascia dentata also showed GDPs. The frequency of these events (1.46 ± 1.25 GDPs/min, n = 7) is significantly lower when compared with that from CA3 (3.13 ± 1.43 GDPs/min, n = 10) or CA1 (2.94 ± 1.36 GDPs/min, n = 17). Dual recordings from CA3 and fascia dentata cells showed synchronous bursts in both regions with no prevalent preceding area. By recording from isolated areas we found that CA1, CA3 and the fascia dentata can produce GDPs, suggesting that they emerge as a property of local circuits present throughout the hippocampus.
Expression of small‐conductance calcium‐activated potassium channels (SK) in outer hair cells of the rat cochlea
Authors: Dulon Didier , Luo Lin , Zhang Chunyan , Ryan Allen F.
Published: March 2003

Physiological evidence suggests that SK‐type Ca2+‐activated K+ channels participate in ACh‐induced hyperpolarization of OHCs (outer hair cells). Based on the sequences published by Köhler et al. (1996, Science, 273: 1709), we designed degenerated primers recognizing cDNA subunits of rSK1, rSK2 and rSK3. Using this concensus set of primers, we probed by PCR a rat organ of Corti cDNA library. Two PCR products of 707 base pairs with sequence identical to rSK3 and rSK2 were obtained and cloned to generate RNA probes for in situ hybridization in the rat cochlea. The subunit rSK2 showed hybridization in the organ of Corti, at the location of the OHCs. The expression of rSK2 by OHCs was confirmed by probing with PCR a poly(A) amplified OHC cDNA library. During development, rSK2 hybridization in the organ of Corti was negative at embryonic days E16, E18 and at P0, weak at P4 and stronger from P8 to adulthood. The subunit rSK2 could also be detected in the spiral ganglion from P4 to the adult stage. Contrary to rSK2, the subunit rSK3 did not show specific hybridization in the organ of Corti at the adult stage (P120) and only a weak expression was observed at P10 and P21. Our study demonstrates expression of rSK2 in OHCs. These potassium channels are good candidates to underlie the ACh‐activated K+ currents recorded during patch‐clamp recordings in isolated OHCs. The expression of rSK2 in the cochlear ganglion at the adult stage suggests that SK Ca2+‐activated K+ channels may also participate in the repolarization of the auditory neurons after the action potential and may influence their firing patterns.
Structural diversity of the voltage‐dependent Ca2+ channel α1E‐subunit
Authors: Pereverzev A. , Klöckner U. , Henry M. , Grabsch H. , Vajna R. , Olyschläger S. , Viatchenko‐Karpinski S. , Schröder R. , Hescheler J. , Schneider T.
Published: March 2003

Voltage‐operated Ca2+ channels are heteromultimeric proteins. Their structural diversity is caused by several genes encoding homologous subunits and by alternative splicing of single transcripts. Isoforms of α1 subunits, which contain the ion conducting pore, have been deduced from each of the six cDNA sequences cloned so far from different species. The isoforms predicted for the α1E subunit are structurally related to the primary sequence of the amino terminus, the centre of the subunit (II–III loop), and the carboxy terminus. Mouse and human α1E transcripts have been analysed by reverse transcription–polymerase chain reaction and by sequencing of amplified fragments. For the II–III loop three different α1E cDNA fragments are amplified from mouse and human brain, showing that isoforms originally predicted from sequence alignment of different species are expressed in a single one. Both predicted α1E cDNA fragments of the carboxy terminus are identified in vivo. Two different α1E constructs, referring to the major structural difference in the carboxy terminus, were stably transfected in HEK293 cells. The biophysical properties of these cells were compared in order to evaluate the importance in vitro of the carboxy terminal insertion found in vivo. The wild‐type α1E subunit showed properties, typical for a high‐voltage activated Ca2+ channel. The deletion of 43 amino acid residues at the carboxy terminus does not cause significant differences in the current density and the basic biophysical properties. However, a functional difference is suggested, as in embryonic stem cells, differentiated in vitro to neuronal cells, the pattern of transcripts indicative for different α1E isoforms changes during development. In human cerebellum the longer α1E isoform is expressed predominantly. Although, it has not been possible to assign functional differences to the two α1E constructs tested in vitro, the expression pattern of the structurally related isoforms may have functional importance in vivo.