bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential regulation of distinct phenotypic features of serotonergic neurons by bone morphogenetic proteins
Authors: Galter Dagmar , Böttner Martina , Krieglstein Kerstin , Schömig Edgar , Unsicker Klaus
Published: March 2003

Bone morphogenetic proteins (BMPs), growth and differentiation factor 5 (GDF5) and glial cell line‐derived neurotrophic factor (GDNF) are members of the transforming growth factor‐β superfamily that have been implicated in tissue growth and differentiation. Several BMPs are expressed in embryonic and adult brain. We show now that BMP‐2, –6 and –7 and GDF5 are expressed in the embryonic rat hindbrain raphe. To start to define roles for BMPs in the regulation of serotonergic (5‐HT) neuron development, we have generated serum‐free cultures of 5‐HT neurons isolated from the embryonic (E14) rat raphe. Addition of saturating concentrations (10 ng/mL) of BMP‐6 and GDF5 augmented numbers of tryptophan hydroxylase (TpOH) ‐immunoreactive neurons and cells specifically taking up 5,7‐dihydroxytryptamine (5,7‐DHT) by about two‐fold. Alterations in 5‐HT neuron numbers were due to the induction of serotonergic markers rather than increased survival, as shown by the efficacy of short‐term treatments. Importantly, BMP‐7 selectively induced 5,7‐DHT uptake without affecting TpOH immunoreactivity. BMP‐6 and –7 also promoted DNA synthesis and increased numbers of cells immunoreactive for vimentin and glial fibrillary acidic protein (GFAP). Pharmacological suppression of cell proliferation or glial development abolished the induction of serotonergic markers by BMP‐6 and –7, suggesting that BMPs act indirectly by stimulating synthesis or release of glial‐derived serotonergic differentiation factors. Receptor bodies for the neurotrophin receptor trkB, but not trkC, abolished the BMP‐mediated effects on serotonergic development, suggesting that the glia‐derived factor is probably brain‐derived neurotrophic factor (BDNF) or neurotrophin‐4. In support of this notion, we detected increased levels of BDNF mRNA in BMP‐treated cultures. Together, these data suggest both distinct and overlapping roles of several BMPs in regulating 5‐HT neuron development.
Rapid glucocorticoid effects on excitatory amino acid levels in the hippocampus: a microdialysis study in freely moving rats
Authors: Venero César , Borrell José
Published: March 2003

Glucocorticoids can rapidly affect neuronal function and behaviour in mammals. Several studies have suggested the possible existence of rapid, non‐genomic effects of glucocorticoids in the hippocampus. To investigate whether glucocorticoids could affect neurotransmission in the hippocampus through rapid, non‐genomic mechanisms, we studied the effects of acute glucocorticoid administration on extracellular amino acid levels in the CA1 area of the hippocampus. By means of microdialysis on freely moving rats, we observed that an intraperitoneal injection of corticosterone (2.5 mg/kg) induced a rapid (within 15 min) and transient (returning to basal levels by 35–45 min) increase in extracellular aspartate and glutamate levels (∼ 155–160%), both in sham‐operated and adrenalectomized rats. These effects occurred in parallel with a rise in corticosterone concentration, also detected by microdialysis, in this hippocampal area. Intrahippocampal perfusion of corticosterone by retrodialysis also produced the same fast and reversible effects on excitatory amino acid (EAA) levels. Extracellular concentrations of taurine and γ‐aminobutyric acid (GABA) were unchanged after intrahippocampal glucocorticoid administration. This corticosterone‐mediated rise in EAA levels was not inhibited by the presence of specific antagonists for the two types of intracellular corticosteroid receptors, nor by a protein synthesis inhibitor, anisomycin. Perfusion of dexamethasone, a synthetic glucocorticoid, elicited a similar effect to that observed with corticosterone treatment in all studied cases. However, non‐glucocorticoid steroids did not affect amino acid transmission in this hippocampal area. These results indicate that glucocorticoids induce a rapid and transient increase in hippocampal EAA levels in vivo that might be exerted through a novel non‐genomic mechanism of action.
Reversal of glutamate excitotoxicity by activation of PKC‐associated metabotropic glutamate receptors in cerebellar granule cells relies on NR2C subunit expression
Authors: Pizzi Marina , Boroni Flora , Bianchetti Konstantinos Moraitis andrea , Memo Maurizio , Spano PierFranco
Published: March 2003

Stimulation of metabotropic glutamate receptors (mGluRs) belonging to group I has been found to reduce N‐methyl‐ d‐aspartate (NMDA) receptor function in terms of both intracellular calcium concentration ([Ca2+]i) rise and neurotoxicity in cultured cerebellar granule cells. In the present study, we investigated whether the mGluR‐elicited modulation of glutamate responses might rely on the heteromeric composition of NMDA receptor channel. NMDA receptors consist of two distinct groups of subunits: NR1, that is ubiquitously in the receptor complexes; and NR2A–D, that differentiate and potentiate NMDA receptor responses by assembling with NR1. Among NR2 subunits, only NR2A and NR2C mRNAs and relative proteins are detected in cerebellar granule cells at 10 days in vitro. To dissect the involvement of the two different subunits in making the NMDA receptor channel sensitive to modulation by group I mGluR agonists, expression of the NR2C subunit was prevented by treating the cells with specific antisense oligodeoxynucleotide (ODN). The capability of the mGluR agonists, trans‐1‐amino‐cyclopentane‐1,3‐dicarboxylic acid (tACPD, 100 μm) or 3 hydroxyphenylglycine (3HPG, 100 μm), and the protein kinase C (PKC) activator, 4β‐phorbol‐12,13‐dibutyrate (PDBu, 1 μm), to inhibit the function of resultant NMDA receptors was then evaluated. We found that depletion of the NR2C subunit abolished the inhibitory effect of group I mGluR stimulation on glutamate‐induced [Ca2+]i rise and neurotoxicity. The antisense ODN treatment also prevented the inhibitory effect of PDBu on glutamate responses. Conversely, in NR2C‐lacking neurons, both group I mGluRs and PKC stimulation enhanced NMDA receptor‐mediated effects. The present findings indicate that the capability of PKC‐associated mGluRs to modulate native NMDA receptor function relies on the heteromeric configuration of the receptor–channel complex. Particularly, expression of the NR2C subunit is required to make the NMDA receptor sensitive to inhibitory modulation by mGluRs or PKC activation.
Tenascin‐R interferes with integrin‐dependent oligodendrocyte precursor cell adhesion by a ganglioside‐mediated signalling mechanism
Authors: Probstmeier Rainer , Michels Marion , Franz Thomas , Chan Bosco M. C. , Pesheva Penka
Published: March 2003

Oligodendrocyte (OL) lineage progression is characterized by the transient expression of the disialoganglioside GD3 by OL precursor (preOL) cells followed by the sequential expression of myelin‐specific lipids and proteins. Whereas GD3+ preOLs are highly motile cells, the migratory capacity of OLs committed to terminal differentiation is strongly reduced, and we have recently shown that the extracellular matrix protein tenascin‐R (TN‐R) promotes the stable adhesion and differentiation of O4+ OLs by a sulphatide‐mediated autocrine mechanism (O4 is a monoclonal antibody recognizing sulphatides/seminolipids expressed by OLs and in myelin). Using culture conditions that allow the isolation of mouse OLs at distinct lineage stages, here we demonstrate that TN‐R is antiadhesive for GD3+ preOLs and inhibits their integrin‐dependent adhesion to fibronectin (FN) by a disialoganglioside‐mediated signalling mechanism affecting the tyrosine phosphorylation of the focal adhesion kinase. This responsive mechanism appears to be common to various cell types expressing disialogangliosides as: (i) disialogangliosides interfered with the inhibition of cell adhesion of different neural and non‐neural cells on substrata containing TN‐R and FN or RGD‐containing FN fragments. TN‐R interacted specifically with disialoganglioside‐expressing cells or immobilized gangliosides, and ganglioside treatment of TN‐R substrata resulted in a delayed preOL cell detachment as a function of time. We conclude that OL response to one and the same signal in the extracellular matrix critically depends on the molecular repertoire expressed by OLs at different lineage stages and could thus define their final positioning.
The effect of Etomidate on sensory transmission in the dorsal column pathway in the urethane‐anaesthetized rat
Authors: Angel A. , Arnott R. H.
Published: March 2003

The effect of Etomidate, a general anaesthetic, on sensory afferent transmission was measured in the dorsal column pathway in urethane‐anaesthetized rats. Extracellular recordings were made of peripherally evoked responses by single cells in the cuneate nucleus, ventroposterolateral nucleus of the thalamus and laminae IV–VI of the primary somatosensory cortex. Cortical mass responses were also recorded. In further experiments, cortical mass responses were evoked antidromically by stimulation in the pyramidal tract. The effect of incremental administration of Etomidate on evoked responses was recorded. These results are compared with the previously reported effects of urethane, a ‘conventional’ anaesthetic. Etomidate did not alter cuneate or ventroposterolateral thalamic cell responses but it caused a dose‐dependent reduction in cortical cell responsiveness. It failed to alter antidromically evoked cortical mass responses. Etomidate differs from the majority of anaesthetics, which act in the thalamus, and appears to cause perturbation at the cortical level.
Architecture and connections of retrosplenial area 30 in the rhesus monkey (macaca mulatta).
Authors: Morris Renée , Petrides Michael , Pandya Deepak N.
Published: March 2003

Because of the sharp curvature of the retrosplenial region around the splenium of the corpus callosum, standard coronal sections are not appropriate for architectonic analysis of its posteroventral part. In the present study, examination of the posteroventral retrosplenial region of the rhesus monkey in sections that were orthogonal to its axis of curvature (and therefore appropriate for architectonic analysis) has permitted definition of its architecture and precise extent. This analysis demonstrated that areas 29 and 30 of the retrosplenial cortex, as well as adjacent area 23 of the posterior cingulate cortex, extend together as an arch around the splenium of the corpus callosum and maintain their topographical relationship with one another throughout their entire course. Injections of anterograde and retrograde tracers confined to retrosplenial area 30 revealed that this area has reciprocal connections with adjacent areas 23, 19 and PGm, with the mid‐dorsolateral part of the prefrontal cortex (areas 9, 9/46 and 46), with multimodal area TPO in the superior temporal sulcus, as well as the posterior parahippocampal cortex, the presubiculum and the entorhinal cortex. There are also bidirectional connections with the lateroposterior thalamic nucleus, as well as the laterodorsal and the anteroventral limbic thalamic nuclei. The connectivity of area 30 suggests that it may play a role in working memory processes subserved by the mid‐dorsolateral frontal cortex in interaction with the hippocampal system.
Acute reorganization of the forepaw representation in the rat SI cortex after focal cortical injury: neuroprotective effects of piracetam treatment
Authors: Coq Jacques‐Olivier , Xerri Christian
Published: March 2003

Immediate postlesion reorganization of the somatosensory cortical representation was examined in adult rats. Response properties of small clusters of neurons were recorded in the area of the primary somatosensory cortex (SI) devoted to the contralateral forepaw representation. Electrophysiological maps were elaborated on the basis of the sensory ‘submodality’ (cutaneous or noncutaneous) and the location of the peripheral receptive fields (RFs) of layer IV neurons. Recordings were made prior to, and from 1 to 12 h after, induction of a focal neurovascular lesion to the SI cortex that initially destroyed a part (8.5%) of the cutaneous representation. Moreover, the influence of an anti‐ischaemic substance (piracetam) on lesion‐induced changes was analysed. The main observations were: (i) a gradual outward expansion of the area of the functional lesion, which was smaller in the piracetam‐treated (PT) rats than in the control, placebo‐treated (PL) rats; (ii) a substantial remodelling of the spared representational zones, both in cortical sectors adjoining the site of injury and those remote from the site; (iii) a significant postlesion increase in the size of cutaneous RFs in the PT rats, but not in the PL rats; (iv) a better preservation of RF submodality and topographic organization in the PT maps than in the PL maps; and (v) a decrease in neuronal responsiveness to cutaneous stimulation which was less pronounced in the PT than in the PL rats. Our results can be ascribed to a rapid change in the balance of excitatory and inhibitory connections which leads to unmasking of subthreshold inputs converging onto cortical neurons. Our findings also indicate that acute piracetam treatment exerts a protective function on the physiological response properties of cortical neurons after focal injury.
Allatostatin modulates skeletal muscle performance in crustaceans through pre‐ and postsynaptic effects
Authors: Kreissl Sabine , Weiss Torsten , Djokaj Stefan , Balezina Olga , Rathmayer Werner
Published: March 2003

Allatostatins, originally identified in insects as peptide inhibitors of juvenile hormone biosynthesis, are regarded as potent inhibitory regulators of intestinal muscles in insects and crustaceans. However, accumulating data indicate that allatostatins might also be involved in modulation of skeletal neuromuscular events. We show that most ganglia of two isopod crustaceans (Idotea baltica and I. emarginata) contain pairs of large, allatostatin‐immunoreactive motor neurons which supply several segmental muscles. Among them are the dorsal extensor muscles, of which some fibres receive immunoreactive, varicose innervation. We demonstrate, on identified muscle fibres, that allatostatin exerts a twofold inhibitory effect: it reduces contractions of single voltage‐clamped fibres, and it decreases the amplitude of evoked excitatory junctional currents recorded from individual release boutons. No change in excitation‐contraction threshold or in passive membrane parameters was observed. As the amplitude of miniature currents generated by spontaneously released single transmitter quanta was not changed, the inhibitory effect of the peptide on junctional currents must be of presynaptic origin. Supportive results were obtained on leg muscles of the crab Eriphia spinifrons, where allatostatin decreased evoked synaptic currents by reducing the mean number of transmitter quanta released by presynaptic depolarization without affecting the amplitudes of currents generated by single quanta. This effect of allatostatin was similar for two functionally different neurons, the slow and the fast closer excitor.

The data show that allatostatin occurs in identified motor neurons of Idotea and exerts complementary pre‐ and postsynaptic modulatory effects which reduce muscle responses. Thus, allatostatin counteracts the effects of another neuropeptide, proctolin, which is also present in Idotea and causes potentiating effects on the same muscle fibres.
Immunological evidence that the β isoform of Ca2+/calmodulin‐dependent protein kinase IV is a cerebellar granule cell‐specific product of the CaM kinase IV gene
Authors: Sakagami Hiroyuki , Umemiya Masashi , Kobayashi Takeshi , Saito Sachiko , Kondo Hisatake
Published: March 2003

Ca2+/calmodulin‐dependent protein kinase IV (CaM kinase IV) exists as two monomeric isoforms, α and β. In this study, we raised an antibody against the β isoform and provided immunohistochemical evidence for specific expression of the β isoform in cerebellar granule cells as a single gene‐derived translational product distinct from the α isoform. Immunohistochemical examination showed that the β‐immunoreactivity was confined to the nuclei of the cerebellar granule cells, in contrast to the more widespread immunoreactivity for the α isoform in both nuclei and cytoplasm of the cerebellar granule cells and many other neurons with dominant nuclear localization. In developing cerebella, the β‐immunoreactivity gradually appeared in the internal granule cells during the postnatal 2nd and 3rd weeks, while the α‐immunoreactivity had already appeared in the internal granule cells in the 1st postnatal week. Unlike the α isoform, β‐immunoreactivity was not detected in the Purkinje cells at any developmental stages. The differential expression of the α and β isoforms suggests that each isoform may be involved in different cerebellar functions.
Expression of nicotinic acetylcholine receptor subunits in the cerebral cortex in Alzheimer’s disease: histotopographical correlation with amyloid plaques and hyperphosphorylated‐tau protein
Authors: Wevers A. , Monteggia L. , Nowacki S. , Bloch W. , Schütz U. , Lindstrom J. , Pereira E. F. R. , Eisenberg H. , Giacobini E. , De Vos R. A. I. , Steur E. N. H. Jansen , Maelicke A. , Albuquerque E. X. , Schröder H.
Published: March 2003

Abstract

Impairment of cholinergic transmission and decreased numbers of nicotinic binding sites are well‐known features accompanying the cognitive dysfunction seen in Alzheimer’s disease (AD). In order to elucidate the underlying cause of this cholinoceptive dysfunction, the expression of two pharmacologically different nicotinic acetylcholine receptor (nAChR) subunits (α4, α7) was studied in the cerebral cortex of Alzheimer patients as compared to controls. Patch‐clamp recordings of 14 dissociated neurons of control cortices showed responses suggesting the existence of α4‐ and α7‐containing functional nAChRs in the human cortex. In cortices of Alzheimer patients and controls, the pattern of distribution and the number of α4 and α7 mRNA‐expressing neurons were similar, whereas at the protein level a decrease in the density of α4‐ and α7‐expressing neurons of ≈ 30% was observed in Alzheimer patients. The histotopographical correlation of nAChR expression with accompanying pathological changes, e.g. accumulation of hyperphosphorylated‐tau (HP‐tau) protein and β‐amyloid showed that neurons in the vicinity of β‐amyloid plaques bore both nAChR transcripts. Neurons heavily labelled for HP‐tau, however, expressed little or no α4 and α7 mRNA. These results point to an impaired synthesis of nAChRs on the protein level as a possible cause of the cholinoceptive deficit in AD. Further investigations need to elucidate whether interactions of HP‐tau with nAChR mRNA, or alterations in the quality of α4 and α7 transcripts give rise to decreased protein expression at the level of individual neurons.
Post‐translational modifications of ICA512, a receptor tyrosine phosphatase‐like protein of secretory granules
Authors: Hermel Jean‐Michel , Dirkx Ronald , Solimena Michele
Published: March 2003

The autoantigen of type I diabetes ICA512 is a receptor tyrosine phosphatase‐like protein enriched in the secretory granule membranes of neurons and peptide secreting endocrine cells. While the function of ICA512 remains unknown, it is thought to link regulated neuropeptide and peptide hormone secretion with signal transduction pathways involving tyrosine phosphorylation/dephosphorylation. To characterize further its biochemical properties, we conducted studies in the bovine pituitary, an abundant source of native ICA512, as well as in fibroblasts transfected with various human ICA512 cDNA constructs. Based on these studies we have established that the signal peptide of ICA512 encompasses residues 1–34 and that the ectodomain of ICA512 undergoes multiple post‐translation modifications, including N‐glycosylation. Newly synthesized ICA512 appears first as a pro‐protein of 110 kDa that is then converted by post‐translational modifications into a 130‐kDa species. Cleavage of pro‐ICA512 at a consensus for furin‐like convertases generates a 60–66‐kDa ICA512 transmembrane fragment (amino acids 449–979). Such processing ICA512 is not restricted to neuroendocrine cells, as it can also occur in transfected fibroblasts. Finally, the predicted N‐terminal fragment of ICA512 resulting from this cleavage (amino acids 35–448) or parts thereof are present in the neurosecretosomes of posterior pituitary, raising the possibility that they may be secreted upon exocytosis of secretory granules.
Cerebellar Golgi cells in the rat: receptive fields and timing of responses to facial stimulation
Authors: Vos Bart P. , Volny‐Luraghi Antonia , De Schutter Erik
Published: March 2003

Golgi cells are the only elements within the cerebellar cortex that inhibit granule cells. Despite their unique position there is little information on how Golgi cells respond to afferent input. We studied responses of Golgi cells to mechanical stimulation of the face, in Crus I‐II of ketamine‐xylazine anaesthetized rats. In 41 rats, 87 putative Golgi cells were identified, based on spike characteristics and on location of electrolytic lesions in the granular layer. They displayed a slow firing rhythm at rest (8.4 spikes/s). Most Golgi cells (84%) showed excitatory responses to tactile input. Their receptive fields (RFs) included, in 78%, the entire ipsilateral infraorbital nerve territory, and extended, in 14%, to other trigeminal nerve branches and, in 48%, to the contralateral face. Excitatory responses consisted of multiple, precisely timed (± 1 ms) spikes. Most peristimulus time histograms (PSTHs) (69%) showed an early (5–10 ms) and a late (13–26 ms) excitatory component, with each component consisting of a single PSTH peak. In some PSTHs the early component was a double peak (< 4 ms interval). In others, only one, early or late, PSTH peak was observed. The excitatory components were followed by a silent period (28–69 ms latency), the duration of which (13–200 ms) varied with response amplitude. In single cells, response profiles changed with stimulus location. In simultaneously recorded cells, evoked profiles differed for identical stimuli. Differences in RF size between early ‘double’ and ‘single’ peaks suggested that they resulted from direct mossy fibre and parallel fibre input, respectively. Late PSTH peaks were assumed to reflect corticopontine activation.
Astrocytes regulate the developmental appearance of GABAergic and glutamatergic postsynaptic currents in cultured embryonic rat spinal neurons
Authors: Li Yong‐Xin , Schaffner Anne E. , Barker Jeffery L.
Published: March 2003

The effects of astrocytes on the emergence of synaptic transients and excitable membrane properties in cultured, embryonic, rat ventral spinal neurons were studied with electrical and optical recording techniques. Neurons on astrocytes had significantly longer neurites and an accelerated rate of growth in surface membrane during the initial 24 h in culture compared to neurons on poly‐ d‐lysine (PDL). GABAergic (GABA, γ‐aminobutyric acid) and glutamatergic transients appeared spontaneously in co‐cultured neurons by 24 h. GABAergic quanta did not appear in neurons on PDL until 4 days in culture, and glutamatergic transients did not emerge until 7 days in culture. Astrocyte‐conditioned medium (ACM) partially mimicked the effects of direct astrocytic contact. GABAergic transients appeared by 2 days, and glutamatergic signals by 4 days in neurons on PDL exposed to ACM. All of the spontaneous, synaptic‐like transients were eliminated by tetrodotoxin or Ca2+o‐free saline, implicating voltage‐dependent cation channels in their generation. Astrocytes immediately and significantly increased the density of voltage‐dependent Na+ currents compared to neurons on PDL, but by the end of 24 h, Na+ current densities were identical. Electrophysiological and optical recording revealed comparable densities of high‐voltage‐activated (HVA) Ca2+ currents on both co‐cultured neurons and neurons on PDL throughout the first week. However, neurons on astrocytes had significantly greater contributions of P/Q‐type currents and lesser contributions of L‐type currents beginning at 24 h and continuing for 7 days. The contribution of N‐type current was significantly more in co‐cultured neurons only at 24 h. Thus, in vitro, astrocytes help to differentiate specific excitable membrane properties in spinal neurons, along with GABAergic and glutamatergic forms of synaptic transmission.
Opioids modulate cell division in the germinal zone of the late embryonic neocortex
Authors: Reznikov Kyrill , Hauser Kurt F. , Nazarevskaja Galina , Trunova Yulia , Derjabin Vasily , Bakalkin Georgy
Published: March 2003

Opioid effects on cell division in the embryonic cerebral cortex were examined using two experimental approaches: (i) the presence of opioid receptors in the embryonic day 16 mouse neocortex was tested using immunohistochemical techniques; (ii) the values of the indices of [3H]thymidine pulse labelled cells and mitotic indices were estimated in the ventricular zone of the embryonic day 16 mouse neocortex 2.5, 4.5 and 8.5 h after administration to pregnant females of selected opioid receptor agonists or the opioid antagonist naloxone. The immunohistochemical study demonstrated that distinct subpopulations of the ventricular zone cells express μ, δ or κ opioid receptors. Acute exposure of mouse embryos to μ, δ and κ opioid receptor agonists or naloxone differentially affects the indices of [3H] thymidine pulse labelled cells and mitotic indices indicating changes in the cell cycle composition. Treatment with the μ opioid receptor agonist D‐Ala2‐MePhe4, Gly‐ol5‐enkephalin (DAGO), or the partially selective κ opioid receptor agonist bremazocine, increased the [3H]thymidine labelling and mitotic indices. In contrast, the δ receptor agonist (D‐Ser8)‐leucine enkephalin‐Thr (DSLET) produced a decrease in the labelled cell indices and mitotic indices. Naloxone provided a biphasic effect: a decrease in the values of labelled cell indices 2.5 h after naloxone administration, followed by an increase in the values of the indices at 4.5 and 8.5 h. These results suggest that the endogenous embryonic/maternal opioid systems are involved in the regulation of cell division in the ventricular zone of the late embryonic cortex.
Visual‐field‐specific heterogeneity within the tecto‐rotundal projection of the pigeon
Authors: Hellmann Burkhard , Güntürkün Onur
Published: March 2003

The organization of the tecto‐rotundal projection of the pigeon was investigated by means of anterograde and retrograde tracing techniques. Besides the known organization in tecto‐rotundal connectivity, this study additionally demonstrates major variations in the ascending projections of different tectal subfields. We show that the ventral tectum opticum (TO) has significantly more projections onto the nucleus rotundus (Rt) than dorsal tectal areas. This difference coincides with differential innervation densities of afferent fibres within rotundal subregions. While ventral tectal efferents project onto the ventral and central Rt, dorsal tectal efferents mainly arborize within limited areas between the central Rt and its dorsal cap, the nucleus triangularis. Thus, the ventral TO, representing the lower and frontal field of view, exhibits a quantitatively and spatially enhanced projection onto the Rt, as compared with the dorsal TO. The data presented here demonstrate a visual field‐dependent projection pattern of ascending tectal outputs onto different rotundal domains. The data are consistent with behavioural studies, demonstrating tectofugal lesions to suppress visual stimulus analysis mainly within the frontal field of view.
The role of pattern vision in the development ofcortico‐cortical connections
Authors: Zufferey Pascal D. , Jin Fuzi , Nakamura Hiroyuki , Tettoni Laurent , Innocenti Giorgio M.
Published: March 2003

The development of cortico‐cortical connections was studied in kittens deprived of vision by binocular eyelid suture during the formation of axonal arbors and synaptogenesis, i.e. between the second postnatal week and the end of the third postnatal month. Axons originating in area 17 and terminating either in ipsilateral or contralateral visual areas were visualized with biocytin. In ipsilateral areas 17 and 18, distinct clusters of branches begin to form, distally from the injection, during the second half of the first postnatal month, independently of pattern vision. More proximal clusters differentiate during the second postnatal month, and this seems to involve elimination of exuberant axonal branches. In kittens deprived of vision for 3 or more months, beginning before natural eye opening, the distal clusters regress and the proximal ones fail to differentiate. In extrastriate areas, distinct clusters of branches have segregated by the end of the second postnatal month, independently of visual experience; however, in kittens deprived of vision for 2 or more months, one of the clusters was selectively eliminated. In contralateral areas 17 and 18, we found stunted terminal arbors in kittens continuously deprived of vision. This was already noticeable at the end of the first postnatal month. Apparently, in the absence of pattern vision, most axons undergo only limited growth and do not form their characteristic terminal columns. Many of these axons are subsequently eliminated. In contrast, 8 days of vision beginning at natural eye opening and followed by visual deprivation caused a nearly normal development of intrahemispheric and interhemispheric connections. In conclusion, pattern vision appears to validate connections at early stages of their development; this validation is necessary for their further growth and differentiation that can then continue autonomously.
An autoradiographic study of the distribution of binding sites for the novel α7‐selective nicotinic radioligand [3H]‐methyllycaconitine in the mouse brain
Authors: Whiteaker Paul , Davies Andrew R. L. , Marks Michael J. , Blagbrough Ian S. , Potter Barry V. L. , Wolstenholme Adrian J. , Collins Allan C. , Wonnacott Susan
Published: March 2003

[3H]‐Methyllycaconitine ([3H]‐MLA) is a new radioligand with selectivity for α7‐type neuronal nicotinic acetylcholine receptors (nAChRs). In our previous study [Davies, A.R.L., Hardick, D.J., Blagbrough, I.S., Potter, B.V.L., Wolstenholme, A.J. & Wonnacott, S. (1999) Neuropharmacology, 38, 679–690], this radioligand labelled a single class of site in rat brain membranes; its pharmacology and distribution in crudely dissected brain regions closely paralleled that of the well‐established α7‐ligand [125I]‐α‐bungarotoxin. However, a small population of [3H]‐MLA binding sites was apparently insensitive to α‐bungarotoxin. Here we have extended the study to mouse brain, using autoradiography to examine the distribution of [3H]‐MLA and [125I]‐α‐bungarotoxin binding sites. [3H]‐MLA labelled a single class of site in mouse brain membranes with a KD of 2.2 nm and a Bmax of 45.6 fmol/mg protein. Specific binding, defined by unlabelled MLA (Ki = 0.69 nm), was completely inhibited by (–)‐nicotine (Ki = 1.62 μm), whereas α‐bungarotoxin inhibited only 85% of specific binding (Ki = 3.5 nm). The distributions of [125I]‐α‐bungarotoxin and [3H]‐MLA binding sites were compared by autoradiography, and binding was quantitated in 72 brain regions. Binding of both radioligands was highly correlated, with highest densities in the dorsal tegmental nucleus of the pons, colliculi and hippocampus. Serial sections labelled with [3H]‐MLA in the absence or presence of unlabelled MLA or α‐bungarotoxin provided no evidence for any α‐bungarotoxin‐resistant binding. The results are discussed in terms of binding sites that are inaccessible to α‐bungarotoxin in membrane preparations. This study demonstrates the utility of [3H]‐MLA for characterization of α7‐type nicotinic receptors in mammalian brain, and suggests that it labels a population identical to that defined by [125I]‐α‐bungarotoxin.
Highly reproducible spatiotemporal patterns of mammalian embryonic movements at the developmental stage of the earliest spontaneous motility
Authors: Suzue Toshihiko , Shinoda Yoshikazu
Published: March 2003

The principles underlying the variations in patterns of mammalian embryonic movements have not been established. In an attempt to clarify the mechanism that is responsible for the variations in motor patterns, we carried out a precise quantitative spatiotemporal analysis of movements in mouse embryos, using a transplacental perfusion method for the in vitro maintenance of live mammalian embryos. Episodes of spontaneous movements at the inception of motility, at embryonic day 12.5, occurred once every few minutes, lasted for several seconds and consisted of successive movements of body regions, the spatiotemporal patterns of which varied from episode to episode. By analysing and categorizing the patterns of these movements, we found that embryonic movements follow relatively few restricted patterns with respect to the order of the movements of body regions. A further analysis of episodes at high spatiotemporal resolution revealed that most of the episodes in a major category could be classified into two distinct subtypes. Each of these subtypes had its own highly reproducible spatiotemporal patterns of movement. Overall, these results show that early embryonic movements follow relatively few rather stereotyped patterns, and random local fluctuations have little effect on such movement patterns. The appearance of one pattern out of several rather stereotyped patterns may be the main cause of apparent variations in patterns of early embryonic movements. The stereotyped patterns may represent important orderly characteristics of spontaneous embryonic activities that may be involved in the development of orderly structures and functions in higher animals.
A patchy horizontal organization of the somatosensory activation of the rat cerebellum demonstrated by functional MRI
Authors: Peeters R. R. , Verhoye M. , Vos B. P. , Van Dyck D. , Van Der Linden A. , De Schutter E.
Published: March 2003

Blood oxygenation level dependent contrast (BOLD) functional MRI (fMRI) responses, in a 7‐T magnet, were observed in the cerebellum of alpha‐chloralose anaesthetized rats in response to innocuous electrical stimulation of a forepaw or hindpaw. The responses were imaged in both coronal and sagittal slices which allowed for a clear delineation and localization of the observed activations. We demonstrate the validity of our fMRI protocol by imaging the responses in somatosensory cortex to the same stimuli and by showing reproducibility of the cerebellar responses. Widespread bilateral activations were found with mainly a patchy and mediolateral band organization, more pronounced ipsilaterally. Possible parasagittal bands were observed only in contralateral lobule VI. There was no overlap between the cerebellar activations caused by forepaw and hindpaw stimuli. The overall horizontal organization of these responses was quite remarkable. For both stimulation paradigms most of the activation patches were positioned in either a rostral or caudal broad plane running anteroposteriorly through both anterior and posterior cerebellum. The rostral planes were completely separated, with the forepaw activation closer to the surface, while the caudal plane was common to both stimulation protocols. We relate our findings to the known projection patterns of spinocerebellar and cuneocerebellar mossy fibres, and to human fMRI studies.
Type III intermittency in human partial epilepsy
Authors: Velazquez J. L. Perez , Khosravani Houman , Lozano Andres , Bardakjian Berj. L. , Carlen Peter L. , Wennberg Richard
Published: March 2003

A rigorous characterization of the dynamic regimes underlying human seizures is needed to understand, and possibly control, the transition to seizure. Intra‐ or extracranial brain electrical activity was recorded in five patients with partial epilepsy, and the interictal and ictal activity analysed to determine the dynamics of seizures. We constructed first‐return one‐dimensional maps by fitting the scatter plots of interpeak intervals. The features of the mapping indicated that type III intermittency is the dynamic charateristic of the ictal events. This was confirmed using histograms of the durations of the regular phases during seizures. The intermittent regime explains the abrupt transitions observed during ictal events in terms of transient stabilization of the unstable steady state.
Presence of functional neuronal nicotinic acetylcholine receptors in brainstem motoneurons of the rat
Authors: Zaninetti Marc , Tribollet Eliane , Bertrand Daniel , Raggenbass Mario
Published: March 2003

In mammals, nicotinic acetylcholine receptors (nAChRs) play a crucial role in motor control. Muscle‐type nAChRs mediate synaptic excitation of skeletal muscle by motoneurons, and nAChRs are present on Renshaw cells, where they produce recurrent inhibition of spinal motoneurons. We asked whether nAChRs are also present in motoneurons. Whole‐cell recordings were performed on various motor nuclei in brainstem slices of young rats. Neurons were visualized using infrared (IR) videomicroscopy. Acetylcholine (ACh) or the nicotinic agonist, epibatidine, were delivered by pressure microinjection. Facial (VII), hypoglossal (XII) and vagal (X) motoneurons responded to ACh by generating a fast inward current. In VII motoneurons, the ACh effect was mimicked by epibatidine, and nicotine induced a slow inward current and desensitized the ACh‐evoked current. In VII and XII motoneurons, the ACh‐evoked current was blocked by the nicotinic antagonist dihydro‐β‐erythroidine (DHβE), but was unaffected by methyllycaconitine (MLA), an α7‐specific antagonist. By contrast, the ACh‐induced current in X motoneurons was sensitive to MLA. Current–voltage relationships indicated that the currents mediated by either α7‐containing (X) or non‐α7‐containing (VII, XII) nAChRs displayed inward rectification. In accordance with the electrophysiological data, autoradiography revealed that VII, X and XII nuclei of young rats contained binding sites for [3H]epibatidine; binding sites for [125I]α‐bungarotoxin, a selective ligand of α7‐containing nAChRs, were present in X nucleus but were almost undetectable in VII and XII nuclei. Thus, brainstem motoneurons of young rats possess functional nAChRs. They could promote fast synaptic coupling between motoneurons, and thus play a role in somatic and visceral motor functions.
Effects of brain‐derived neurotrophic factor on the development of NADPH‐diaphorase/nitric oxide synthase‐positive amacrine cells in the rodent retina
Authors: Cellerino Alessandro , Arango‐González Blanca Aurora , Kohler Konrad
Published: March 2003

Amacrine neurons expressing nitric oxide synthase (NOS) contain brain‐derived neurotrophic factor (BDNF) receptors and respond to exogenous BDNF [Klöcker, N., Cellerino, A. & Bähr, M. (1998) J. Neurosci., 18, 1038–1046]. We analysed the effects of BDNF on the development of neurons which express NOS in the mouse and rat retina. Rat pups received a total of three intraocular injections of BDNF at intervals of 48 h, starting at postnatal day 16 (P16), and were killed at P22. The retinas were stained for NADPH‐diaphorase, a histological marker of NOS. NOS‐expressing neurons were found in both the inner nuclear layer (INL) and the ganglion cell layer (GCL). Two classes of NOS‐expressing neurons, type I and type II, had already been distinguished in the INL [Koistinaho, J. & Sagar, S.M. (1995) In Osborne, N.N. & Chader, G.J. (eds), Progress in Retinal and Eye Research, Vol. 15. Oxford University Press, pp. 69–87] and a third one in the GCL. Up‐regulation of NADPH‐diaphorase activity was observed after BDNF treatment. The number of type I neurons remained stable, whereas the number of type II neurons and NOS‐positive neurons in the GCL increased significantly (P < 0.001). Type I and type II neurons were significantly larger in BDNF‐treated retinas. Double‐labelling experiments revealed that BDNF induces NADPH‐diaphorase in dopaminergic neurons and amacrine cells displaced to the GCL, but not in retinal ganglion cells. In mice homozygous for a null mutation of the bdnf gene, the intensity of NADPH‐diaphorase labelling in both somata and processes was reduced, but the number of labelled neurons was not dramatically reduced. These findings indicate that BDNF regulates the neurotransmitter phenotype of NOS‐expressing amacrine neurons under physiological conditions, but is not required for their survival.
Subpopulations of GABAergic and non‐GABAergic rat dorsal horn neurons express Ca2+‐permeable AMPA receptors
Authors: Albuquerque Cristóvão , Lee C. Justin , Jackson Alexander C. , MacDermott Amy B.
Published: March 2003

Subpopulations of α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) receptors that are either permeable or impermeable to Ca2+ are expressed on dorsal horn neurons in culture. While both mediate synaptic transmission, the Ca2+ ‐permeable AMPA receptors provide a Ca2+ signal that may result in a transient change in synaptic strength [Gu, J.G., Albuquerque, C., Lee, C.J. & MacDermott, A.B. (1996) Nature, 381, 793]. To appreciate the relevance of these receptors to dorsal horn physiology, we have investigated whether they show selective expression in identified subpopulations of dorsal horn neurons. Expression of Ca2+‐permeable AMPA receptors was assayed using the kainate‐induced cobalt loading technique first developed by Pruss et al. [Pruss, R.M., Akeson, R.L., Racke, M.M. & Wilburn, J.L. (1991) Neuron, 7, 509]. Subpopulations of dorsal horn neurons were identified using immunocytochemistry for γ‐aminobutyric acid (GABA), glycine, substance P receptor (NK1 receptor) and the Ca2+‐binding proteins, calretinin and calbindin D28K. We demonstrate that, in dorsal horn neurons in culture, kainate‐induced cobalt uptake is selectively mediated by Ca2+‐permeable AMPA receptors, and that a majority of GABA and NK1 receptor‐expressing neurons express Ca2+‐permeable AMPA receptors. GABAergic dorsal horn neurons are important in local inhibition as well as in the regulation of transmitter release from primary afferent terminals. NK1 receptor‐expressing dorsal horn neurons include many of the projection neurons in the nociceptive spino‐thalamic pathway. Thus, we have identified two populations of dorsal horn neurons representing important components of dorsal horn function that express Ca2+‐permeable AMPA receptors. Furthermore, we show that several subpopulations of putative excitatory interneurons defined by calretinin and calbindin expression do not express Ca2+‐permeable AMPA receptors.
Subthalamic nucleus lesions induce deficits as well as benefits in the hemiparkinsonian rat
Authors: Henderson Jasmine M. , Annett Lucy E. , Ryan Lawrence J. , Chiang Wesley , Hidaka Seiko , Torres Eduardo M. , Dunnett Stephen B.
Published: March 2003

Lesions of the subthalamic nucleus can restore some imbalances in motor output of the basal ganglia induced by nigrostriatal dopamine depletion, and have been proposed as a potential therapy for Parkinson's disease. Although there is substantial supporting evidence from experimental studies in both rats and primates, there is less information on the effects of subthalamic lesions alone. In order to characterize potential side effects, the present study evaluates the behavioural effects of unilateral excitotoxic lesions of the subthalamic nucleus in rats that have previously received either unilateral saline or 6‐hydroxydopamine injections into the nigrostriatal bundle on the same side. The 6‐hydroxydopamine lesions induced ipsilateral orientation asymmetries in head position and body axis bias, rotational asymmetries following injections of direct or indirect dopamine agonists, neglect of contralateral stimuli, and a reduction in the numbers of pellets retrieved with the contralateral paw in a skilled reaching task. Subsequent excitotoxic lesions of the subthalamic nucleus reduced (but did not abolish) rotational asymmetries, had no effects on the measures of neglect and skilled paw‐reaching, and produced contralateral orientation biases in head turning and body axis curling. Rats that received subthalamic lesions alone exhibited de novo impairments comprising contralateral biases in the orientation tests. These results support a neuromodulatory role of the subthalamic nucleus in regulating motor outputs of the basal ganglia, and caution that there may be distinct side effects of the lesion by itself. Whereas some impairments attributable to dopamine depletion may be alleviated by subthalamic manipulations, other symptoms are not, or may even be aggravated.
Functional and molecular diversity of PACAP/VIP receptors in cortical neurons and type I astrocytes
Authors: Grimaldi Maurizio , Cavallaro Sebastiano
Published: March 2003

In the present study we determined the mRNA‐expression of pituitary adenylate cyclase activating polypeptide (PACAP)/vasoactive intestinal peptide (VIP) receptors in primary cultures of rat cortical neurons and type I astrocytes, and investigated the effects of PACAP38 on adenylyl cyclase, inositol phospholipid hydrolysis and intracellular calcium homeostasis. PACAP38 elicited a concentration‐dependent (1 n m–100 nm) increase in inositol phosphate levels and [Ca2+]i in neurons but not in type I astrocytes. The PACAP‐induced increase of intracellular calcium concentration, [Ca2+]i, was characterized by a spike, compatible with inositol trisphosphate (IP3) ‐induced calcium mobilization from intracellular stores, and a plateau phase, sustained by activation of capacitative calcium entry triggered by depletion of IP3‐sensitive calcium stores. In the absence of extracellular calcium, only the spike phase was present while the plateau phase was clearly reduced. In addition, thapsigargin pretreatment abolished the PACAP38‐induced [Ca2+]i rise. Treatment with 1 μm VIP did not affect [Ca2+]i in either neurons or type I astrocytes, clearly indicating the coupling of PAC1–HOP subtype to phospholipase‐C in neurons. In addition, as previously reported, PACAP38 stimulated cAMP formation in both neurons and type I astrocytes. Using the reverse transcription polymerase chain reaction, we found mRNA‐expression of PAC1 (PACAP – HOP variant) and VPAC2 in neurons, PAC1 (PACAP – R variant), VPAC1 and VPAC2 in astrocytes. These data indicate both a functional and molecular diversity of PACAP and VIP receptors in these cell types and support the view that the PAC1‐HOP variant may be responsible for phospholipase‐C activation and [Ca2+]i elevation in cortical neurons.