bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete localizations of hedgehog signalling components in the developing and adult rat nervous system
Authors: Traiffort Elisabeth , Charytoniuk Dorota , Watroba Laurent , Faure Hélène , Sales Nicole , Ruat Martial
Published: March 2003

Sonic hedgehog (Shh), a morphogen molecule implicated in embryonic tissue patterning, displays inductive, proliferative, neurotrophic and neuroprotective activities on various neural cells. Shh might exert its biological functions through binding to patched (Ptc) associated with smoothened (Smo), leading to downstream activation of target genes such as the transcription factor Gli1. We have performed a detailed localization of cells expressing transcripts of Shh, Ptc, Smo and Gli1 in brain and spinal cord of the adult rat as well as in the developing cerebellum. In the adult, Shh‐positive cells were mainly observed in forebrain structures, in the Purkinje cells of the cerebellum and in motor neurons. Ptc‐positive cells were frequently observed in brain areas devoid of any Shh transcripts, except in the median eminence or the facial nucleus, suggesting local Shh signalling. Interestingly, Smo transcripts were predominantly present within circumventricular organs, in granular cells of the dentate gyrus and in neurons of the reticular thalamic nucleus. The presence of Shh, Ptc and Smo transcripts in hypothalamic areas may indicate a role of Shh signalling in the modulation of neuroendocrine functions. The expression pattern of these three genes as well as of Gli1, and their developmental regulation in the cerebellum, suggest a possible role for Hedgehog signalling in the control of various cell populations within the cerebellum, particularly in granule cell proliferation and/or differentiation that might be impaired in proliferative states such as medulloblastomas.
Redistribution of presynaptic proteins during α‐latrotoxin‐induced release of neurotransmitter and membrane retrieval at the frog neuromuscular junction
Authors: Boudier Jeanne‐Andrée , Martin‐Moutot Nicole , Boudier Jean‐Louis , Iborra Cecile , Takahashi Masami , Seagar Michael J.
Published: March 2003

Calcium‐dependent exocytosis at the nerve terminal involves the synaptic core (SNARE) complex composed of the t‐SNAREs syntaxin 1 and synaptosome‐associated protein of 25 kDa (SNAP‐25), and the v‐SNARE vesicle‐associated membrane protein (VAMP/synaptobrevin), a stable heterotrimer which can associate with the putative calcium sensor protein, synaptotagmin. The distribution of these proteins at the frog neuromuscular junction was examined by immunofluorescent staining and confocal microscopy following exocytosis induced by α‐latrotoxin. Experiments were performed under conditions in which synaptic vesicle recycling was either maintained in balance with exocytosis, or completely blocked, or during recovery from block of endocytosis. When endocytosis was maintained, protein distribution was essentially identical to that of unstimulated nerve terminals, in which syntaxin 1 and SNAP‐25 are localized to the presynaptic active zones coincident with the postsynaptic folds that contain a high density of acetylcholine receptors (AChRs). Block of endocytosis led to complete incorporation of vesicle proteins into the plasmalemma, and t‐SNARE distribution was no longer restricted to active zones. Five minutes after the onset of recovery, both synaptic vesicle proteins and t‐SNARE proteins were concentrated into small spots, in a similar pattern to that obtained following endocytosis of the vital styryl dye FM1‐43. These findings are consistent with a model in which following sustained exocytosis, t‐SNARE trafficking involves internalization and transit via a vesicular compartment before recycling to the presynaptic plasma membrane.
Acetylcholine suppresses the spread of excitation in the visual cortex revealed by optical recording: possible differential effect depending on the source of input
Authors: Kimura Fumitaka , Fukuda Mitsuhiro , Tsumoto Tadaharu
Published: March 2003

Optical recording with a voltage‐sensitive dye was performed in visual cortical slices of the rat to determine the effect of acetylcholine (ACh) on the spread of excitation. In the presence of ACh, the spread of excitation initiated by stimulation at the white matter/layer VI (WM/VI) was greatly suppressed throughout the cortex, with less suppression in the middle layers. By comparing the effect of ACh with that of 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), the fraction of the synaptic component that was sensitive to ACh was evaluated. ACh suppressed ∼ 40–50% (maximum 55.8%, n = 11) of the initial synaptic component in the superficial and deep layers. In the middle, however, the effect was weakest and only ∼ 20–30% (minimum 20.9%, n = 11) of the initial synaptic component was suppressed. On the basis of histological analysis, the region with the weakest ACh effect extended from upper V to lower II/III. To identify the site of ACh action in terms of pre‐ versus postsynaptic localization, exogenous glutamate was applied. Because ACh did not suppress the excitation induced by glutamate, the site of the ACh action was indicated to be presynaptic. When layer II/III was stimulated instead of WM/VI, the suppression was uniform throughout the cortex. A muscarinic receptor antagonist, atropine, blocked the suppression by ACh. In conclusion, our results indicate the following two points. First, ACh strongly suppresses intracortical connectivity through presynaptic muscarinic receptors. Secondly, in contrast to the intracortical connection, some group(s) of fibres, possibly thalamocortical afferents that arise from white matter and terminate in the middle cortical layers are suppressed much less by ACh. While ACh has been reported to have confusingly diverse effects, e.g. direct depolarization and hyperpolarization as well as synaptic facilitation and suppression, its effect on the propagation of excitation is very clear; suppression on intracortical connection, leaving thalamocortical inputs rather intact. We postulate that cholinergic innervation enables the afferent input to have a relatively dominant effect in the cortex.
Functional NMDA and GABAA receptors in pioneer neurons of the cortical marginal zone
Authors: Soria José Miguel , Martínez‐Galán Juan Ramón , Luján Rafael , Valdeolmillos Miguel , Fairén Alfonso
Published: March 2003

Transient pioneer neurons in the neocortical marginal zone generate an early corticofugal axonal projection at E12–E16 (Meyer et al. 1998). We have analysed the functional activity of glutamate and GABA receptors in such cells by measuring changes in intracellular calcium concentrations ([Ca2+]i). The activation of GABAA receptors with muscimol, as well as bath application of glutamate, lead to increases in [Ca2+]i in pioneer neurons. The stimulatory action of glutamate is mostly produced through the NMDA‐type of ionotropic receptors. Metabotropic glutamate receptor activation has no effect on [Ca2+]i. Consistent with such results, immunocytochemical studies showed a prominent expression of GABAA and NMDA receptors in pioneer neurons. The activation of such receptors may be implicated in the remodelling of pioneer neurons during development.
Endogenous adenosine protects CA1 neurons from kainic acid‐induced neuronal cell loss in the rat hippocampus
Authors: Matsuoka Yasuji , Okazaki Mitsuhiro , Takata Kazuyuki , Kitamura Yoshihisa , Ohta Shyunsaku , Sekino Yuko , Taniguchi Takashi
Published: March 2003

CA3 pyramidal neurons in the rat hippocampus show selective vulnerability to the intracerebroventricular injection of kainic acid (KA). However, the mechanism of this selective neuronal vulnerability remains unclear. In this study, we examined the contribution of endogenous adenosine, a potent inhibitory neuromodulator, to the differences in the neuronal vulnerability of the hippocampus, using microtubule‐associated protein (MAP)‐2, phosphorylated c‐Jun, and major histocompatibility complex (MHC) class II immunoreactivities as markers for neuronal cell loss, neuronal apoptosis and glial activation, respectively. Pretreatment with 8‐cyclopenthyltheophylline (CPT), an A1 adenosine receptor antagonist, significantly exacerbated KA‐induced neuronal cell loss in both the CA1 and CA3. Although c‐Jun phosphorylation, a critical step in neuronal apoptosis, was not detected in the vehicle‐injected rat hippocampus, c‐Jun phosphorylation was induced in the CA3 by the injection of KA alone. Pretreatment with CPT induced c‐Jun phosphorylation in both the CA1 and CA3. MHC class II antigen was also detected in the regions of c‐Jun phosphorylation. Coadministration of N6‐cyclopenthyladenosine (CHA), an A1 adenosine receptor agonist, attenuated the neuronal cell loss in the CA1 and CA3 with or without pretreatment with CPT. These results strongly suggest that endogenous adenosine has neuroprotective effects against excitotoxin‐induced neurodegeneration in the CA1 through its A1 receptors.
Previous maternal experience potentiates the effect of parturition on oxytocin receptor mRNA expression in the paraventricular nucleus
Authors: Broad K. D. , Lévy F. , Evans G. , Kimura T. , Keverne E. B. , Kendrick K. M.
Published: March 2003

In sheep, central oxytocin release at parturition induces maternal behaviour which is thought to be mediated by changes in the expression of central oxytocin receptors. The distribution, effects of parturition, previous maternal experience and hormonal status on the distribution of an oxytocin receptor was investigated using immunocytochemistry and in situ hybridization. In ewes with no previous maternal experience, parturition induced significant increases in oxytocin receptor mRNA expression in the anterior olfactory nucleus, medial preoptic area, ventromedial hypothalamus, lateral septum, medial amygdala, bed nucleus of the stria terminalis and diagonal band of Broca. In maternally experienced ewes, parturition induced additional increases in two areas, the paraventricular nucleus and the Islands of Calleja. The changes in progesterone and oestrogen that occur during late pregnancy and parturition appear to contribute to increases in expression in the anterior olfactory nucleus, Islands of Calleja, medial preoptic area, ventromedial hypothalamus, bed nucleus of the stria terminalis and diagonal band of Broca, but not in the paraventricular nucleus, lateral septum and medial amygdala. These results demonstrate that progesterone and oestrogen priming enhance oxytocin receptor mRNA expression in a number of regions in the olfactory system, hypothalamus and limbic brain. These effects appear to be independent of maternal experience. Parturition increases oxytocin receptor mRNA expression in all the areas influenced by hormonal priming and the lateral septum, medial amygdala and paraventricular nucleus. Maternal experience also enhances expression of oxytocin receptor mRNA in the paraventricular nucleus and the Islands of Calleja. Because the paraventricular nucleus is the main source of oxytocin release in the brain, this upgrading of autoreceptors as a result of maternal experience may serve to enhance release of this peptide in projection sites regulating maternal behaviour.
Functional circuitry for the induction of prolonged excitation in the rat spinal dorsal horn
Authors: Murase Kazuyuki , Saka Takashi , Asai Tatsuya , Ikeda Hiroshi
Published: March 2003

The neuronal circuitry through which prolonged excitation is generated in the spinal dorsal horn was investigated using optical imaging of neuronal excitation in transverse slices of rat spinal cords. It is known that tetanic stimulation (20 Hz for 1 s) of the dorsal root that activates both A and C primary afferent fibres elicits slow intrinsic optical signals (IOS) in the dorsal horn, seen most intensely in the substantia gelatinosa (SG), lamina II, and that IOS expresses in part the slow synaptic response recorded intracellularly in dorsal horn neurons. We here report that the slow IOS within the SG were completely abolished after an incision was made at the border between the SG and the deeper laminae, but not after an incision within the deeper dorsal horn of the laminae III–V. The result demonstrates directly that, in order to generate prolonged excitation in the SG, the neuronal elements in the deeper dorsal horn must be intact. Thus, the afferent information might be received first by the deeper elements and then transmitted to the SG region, and/or collaboration between the SG and deeper elements is necessary to maintain prolonged excitation in the SG.
Regional brain activity during shape recognition impaired by a scopolamine challenge to encoding
Authors: Rosier Anne‐Marie , Cornette Luc , Dupont Patrick , Bormans Guy , Mortelmans Luc , Orban Guy A.
Published: March 2003

In the present positron emission tomography (PET) study, we examine the effect of a scopolamine‐induced challenge to encoding upon the pattern of regional cerebral blood flow during recognition of a list of abstract visual shapes 3 days after encoding of these shapes. This study was conducted to test hypotheses concerning the fusiform and thalamic contributions to object recognition arising from a previous imaging study of impaired recognition. In that study, we demonstrated that activity in the fusiform cortex and the thalamus during shape recognition was modulated by memory challenges. These memory challenges included, on one hand, impaired storage as a consequence of diazepam administration during encoding, and, on the other hand, impaired retrieval caused by a perceptual challenge. Activation in the fusiform cortex decreased during impaired recognition, irrespective of the type of challenge. In contrast, thalamic activation increased only when the recognition deficit resulted from impaired memory storage. Based on these results, we hypothesized that fusiform activation during recognition reflects the matching of an incoming stimulus with a stored one, whereas thalamic activation reflects retrieval attempts. These hypotheses would receive considerable support if scopolamine, which also impairs memory storage, induced similar modulations of fusiform and thalamic activation. In the present study, we observed that a scopolamine challenge to encoding does indeed modulate the activity in the very same regions that were previously modulated by a diazepam challenge. Hence, a similar memory deficit, although primarily effected through different neurochemical pathways, was paralleled by a similar modulation of activity in the same set of nodes in the shape recognition network. In the fusiform cortex, scopolamine decreased recognition‐related activity, as did the sensory challenge of retrieval. Furthermore, covariate analysis demonstrated that the level of fusiform activity linearly correlates with behavioural performance. In the thalamus, activation increased following impaired encoding. This is in accordance with the idea that enhanced thalamic activity reflects increased effort expended in retrieval. In addition, in the intraparietal sulcus, differential activation also increased following impaired memory storage, possibly reflecting enhanced visuospatial attention in an effort to compensate for impaired performance.
Carbachol‐induced changes in excitability and [Ca2+]i signalling in projection cells of medial entorhinal cortex layers II and III
Authors: Gloveli Tengis , Egorov Alexei V. , Schmitz Dietmar , Heinemann Uwe , Müller Wolfgang
Published: March 2003

The entorhinal cortex (EC) is a major gateway for sensory information into the hippocampus and receives a cholinergic input from the forebrain. Therefore, we studied muscarinic effects on excitability and intracellular Ca2+ signalling in layer II stellate and layer III pyramidal projection neurons of the EC. In both classes of neurons, local pressure‐pulse application of carbachol (1 mm) caused small, atropine‐sensitive membrane depolarizations that were not accompanied by any detectable changes in [Ca2+]i. At a higher concentration (10 mm), carbachol induced a larger membrane depolarization associated with synaptic oscillations and epileptiform activity in both classes of neurons. In contrast to the intrinsic theta rhythm in stellate cells with one dominant peak frequency at ∼ 7 Hz, the synaptically mediated oscillation induced by carbachol showed three characteristic peaks in the theta and gamma frequency range at ∼ 11, 23 and 40 Hz. Although carbachol‐induced epileptiform activity was associated with increases in intracellular free Ca2+ in both layer II and III cells, the observed [Ca2+]i accumulation was significantly larger in layer III than in layer II cells. Responses to intracellular current injections showed differences in Ca2+ accumulation in layer II and III cells at the same membrane potentials, suggesting a dominant expression of low‐ and high‐voltage‐activated Ca2+ channels in these layer II and III cells, respectively. In conclusion, we present evidence for significant differences in the [Ca2+]i regulation between layer II stellate and layer III pyramidal cells of the medial EC.
1‐Aminoindan‐1,5‐dicarboxylic acid and (S)‐(+)‐2‐(3′‐carboxybicyclo[1.1.1] pentyl)‐glycine, two mGlu1 receptor‐preferring antagonists, reduce neuronal death in in vitro and in vivo models of cerebral ischaemia
Authors: Pellegrini‐Giampietro Domenico E. , Cozzi Andrea , Peruginelli Fiamma , Leonardi Patrizia , Meli Elena , Pellicciari Roberto , Moroni Flavio
Published: March 2003

Metabotropic glutamate (mGlu) receptors have been implicated in a number of physiological and pathological responses to glutamate, but the exact role of group I mGlu receptors in causing postischaemic injury is not yet clear. In this study, we examined whether the recently‐characterized and relatively selective mGlu1 receptor antagonists 1‐aminoindan‐1,5‐dicarboxylic acid (AIDA) and (S)‐(+)‐2‐(3′‐carboxybicyclo[1.1.1]pentyl)‐glycine (CBPG) could reduce neuronal death in vitro, following oxygen‐glucose deprivation (OGD) in murine cortical cell and rat organotypic hippocampal cultures, and in vivo, after global ischaemia in gerbils. When present in the incubation medium during the OGD insult and the subsequent 24 h recovery period, AIDA and CBPG significantly reduced neuronal death in vitro. The extent of protection was similar to that observed with the nonselective mGlu receptor antagonist (+)‐α‐methyl‐4‐carboxyphenylglycine [(+)MCPG] and with typical ionotropic glutamate (iGlu) receptor antagonists. Neuroprotection was also observed when AIDA or CBPG were added only after the OGD insult was terminated. Neuronal injury was not attenuated by the inactive isomer (–)MCPG, but was significantly enhanced by the nonselective mGlu receptor agonist (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid [(1S,3R)‐ACPD] and the group I mGlu receptor agonist 3,5‐dihydroxyphenylglycine (3,5‐DHPG). The antagonists (+)MCPG, AIDA and CBPG were also neuroprotective in vivo, because i.c.v. administration reduced CA1 pyramidal cell degeneration examined 7 days following transient carotid occlusion in gerbils. Our results point to a role of mGlu1 receptors in the pathological mechanisms responsible for postischaemic neuronal death and propose a new target for neuroprotection.
Angiotensin II receptor subtype gene expression and cellular localization in the retina and non‐neuronal ocular tissues of the rat
Authors: Wheeler‐Schilling Thomas H. , Kohler Konrad , Sautter Monika , Guenther Elke
Published: March 2003

In addition to its function as a peripheral hormone, angiotensin II (AngII) has been shown to act as a neuromodulator in various brain regions. AngII effects are mediated by two major AngII receptor subtypes, AT1 and AT2, and different AT1 receptor isoforms AT1A and AT1B are described in rat brains. The purpose of the present study was to analyse the expression pattern of AT receptors in different parts of the rat eye with special emphasis on the retina. Specific primers were constructed and the gene expression of AngII receptor subtypes was investigated by means of reverse transcription‐polymerase chain reaction (RT‐PCR). An antibody was used for cellular localization of AT1 receptor in the retina. AT2 receptor mRNA was localized by in situ hybridization (ISH). We examined the retinas of different developmental stages as well as non‐neuronal ocular tissues, e.g. choroid and anterior uveal tract of rats (Brown Norway and Wistar strain), for the gene expression of AT receptors. Our results show that AT1A and AT2 mRNAs are expressed in rat choroid, iris/ciliary body and retinas, whereas AT1B mRNA is not expressed in the retina but in all other ocular tissues under investigation. AT1 receptor immunohistochemistry of the retina showed strong labelling in the ganglion cell layer (GCL), and some cells in the inner nuclear layer (INL), suggesting putative ganglion cell but also amacrine cell labelling. In the retina, ISH for AT2 mRNA revealed labelling in the GCL and a faint labelling in the inner nuclear layer. No AT2 ISH‐signal was found in the other ocular tissues. These data suggest that there is a specific distribution pattern of AT receptors in rat ocular tissues, especially in the retina. The expression of AT receptors on retinal ganglion cells confirms the AngII action on these cell types and supports the role of AngII as a retinal neurotransmitter or neuromodulator.
Cortical and nigral deafferentation and striatal cholinergic markers in the rat dorsal striatum: different effects on the expression of mRNAs encoding choline acetyltransferase and muscarinic m1 and m4 receptors
Authors: Kayadjanian N. , Schofield W. N. , Andren J. , Sirinathsinghji D. J. S. , Besson M. ‐J.
Published: March 2003

The regulation of the striatal m1 and m4 muscarinic receptor mRNA as well as the choline acetyltransferase (ChAT) mRNA expression by nigral dopaminergic and cortical glutamatergic afferent fibres was investigated using quantitative in situ hybridization histochemistry. The effects induced by a unilateral lesion of the medial forebrain bundle and a bilateral lesion of the sensorimotor (SM) cortex were analysed in the dorsal striatum 3 weeks after the lesions. Dopaminergic denervation of the striatum resulted in a marked decrease in the levels of m4 mRNA throughout the striatum, while the levels of muscarinic m1 mRNA and ChAT mRNA in cholinergic neurons were unaffected by the lesion. In contrast, following bilateral cortical ablation, the levels of the muscarinic m1 mRNA were significantly increased in the striatal projection area of the SM cortex, whereas the expression of m4 mRNA remained unchanged. Single cholinergic cell analysis by computer‐assisted grain counting revealed a decreased labelling for ChAT mRNA per neuron following cortical ablation. However, in contrast to the topographical m1 mRNA changes, the decreased ChAT mRNA expression was evenly distributed within the striatum, suggesting an indirect cortical control upon striatal cholinergic interneurons. Altogether, these data suggest that dopaminergic nigral and glutamatergic cortical afferents modulate differentially cholinergic markers, at the pre‐ and post‐synaptic levels. Beside the fact that nigral and cortical inputs exert an opposite control on cholinergic neurotransmission, our study further shows that this control involved different muscarinic receptor subtypes: the m4 and m1 receptors, respectively.
Tonotopic organization and parcellation of auditory cortex in the FM‐bat Carollia perspicillata
Authors: Esser Karl‐Heinz , Eiermann Arne
Published: March 2003

In the short‐tailed fruit bat (Carollia perspicillata), the auditory cortex was localized autoradiographically and studied electrophysiologically in detail by using metal microelectrodes and 10‐ms tone stimuli. Because, in the weakly‐anaesthetized preparation, neuronal responses to pure‐tones were even found throughout the non‐primary auditory cortex, characteristic frequencies and minimum thresholds of neuron clusters (multiunits) could be mapped consistently and used to define auditory cortical fields conventionally (i.e. as in studies of auditory cortex of non‐echolocating mammals). Thus, within the electrophysiologically demarcated auditory cortex, six auditory fields were defined by criteria, as for example a gradient of characteristic frequencies (primary auditory cortex, AI; anterior auditory field, AAF; secondary auditory cortex, AII), reversal of the gradient across the field border (AI, AAF), uniform representation of a restricted band of frequencies (i.e. > 60 kHz; high‐frequency fields I and II, HFI and HFII), and transition from low to high minimum thresholds or vice versa [dorsoposterior field (DP), AII, HFI, HFII]. As supportive evidence for the distinction of these auditory cortical fields, differences in neuronal response properties were also used. In comparison with other mammals (e.g. cat and mouse), both the relative position of the auditory fields (mainly AI, AAF, DP and AII) and the representational principles for sound parameters within these forebrain areas seem to reflect a ‘fundamental plan’ (discussion below) of mammalian auditory cortical organization. Two coherent dorsally displaced high‐frequency representations (HFI, HFII) covering ∼ 40% of the total auditory cortical surface seem particularly suited for the processing of the dominant biosonar second and third harmonic of this species, and hence can be regarded as an adaptation for echolocation.
Differential neuronal responsiveness in primate perirhinal cortex and hippocampal formation during performance of a conditional visual discrimination task
Authors: Xiang J. ‐Z. , Brown M. W.
Published: March 2003

Neuronal responses in the hippocampal formation, including the entorhinal cortex, have been compared with those in the inferior temporal cortex, including the perirhinal cortex, during performance by monkeys of a visual conditional discrimination task. In the task, the arrangement of three geometric shapes determined the correctness of either a left or right behavioural response according to a conditional rule. Neurons that responded differently to different types of trial were common (50% of the visually responsive neurons) in the entorhinal cortex, perirhinal cortex and area TE of the inferior temporal cortex, but significantly less common in the hippocampus (13%). This differential incidence suggests a more important role for the rhinal cortices and area TE than for the hippocampus in this task. Based on the neuronal responses, arguments are advanced that the animals probably solved the task by a strategy that did not require spatial or hippocampal processing. Thus, of the differential responses, those that would allow the animals to solve the task by using a conditional rule and so avoid spatial processing were twice as common (37%) as those allowing solution to be by selection of a particular spatially directed response to each arrangement of shapes (19%). Moreover, the differential latencies of responses that allowed the task to be solved by a conditional rule were shorter (< ∼ 165 ms), and hence processing was faster, than those that provided information about particular individual types of trial (∼ 195 ms). Even so, hippocampal responsiveness in the conditional task was differentially enhanced when compared with that during a recognition memory task, and the neuronal responses potentially allow the animal to employ a second, alternative strategy that might be expected to depend on hippocampal processing.
CNS‐specific prostacyclin ligands as neuronal survival‐promoting factors in the brain
Authors: Satoh Takumi , Ishikawa Yasuyuki , Kataoka Yosky , Cui Yilong , Yanase Hisato , Kato Koichi , Watanabe Yumiko , Nakadate Kazuhiko , Matsumura Kiyoshi , Hatanaka Hiroshi , Kataoka Kiyoshi , Noyori Ryoji , Suzuki Masaaki , Watanabe Yasuyoshi
Published: March 2003

Prostacyclin (PGI2) is a critical regulator of the cardiovascular system, via dilatation of vascular smooth muscle and inhibition of platelet aggregation (Moncada, S. 1982, Br. J. Pharmacol., 76, 3). Our previous studies demonstrated that a novel subtype of PGI2 receptor, which is clearly distinct from a peripheral subtype in terms of ligand specificity, is expressed in the rostral region of the brain, e.g. cerebral cortex, hippocampus, thalamus and striatum, and that (15r)‐16‐m‐17,18,19,20‐tetranorisocarbacyclin (15r‐TIC) and 15‐deoxy‐16‐m‐17,18,19,20‐tetranorisocarbacyclin (15‐deoxy‐TIC) specifically bind to the central nervous system (CNS)‐specific PGI2 receptor. Here, we report that these CNS‐specific PGI2 receptor ligands, including PGI2 itself, prevented the neuronal death. They prevented apoptotic cell death of hippocampal neurons induced by high (50%) oxygen atmosphere, xanthine + xanthine oxidase, and serum deprivation. IC50s for neuronal death were ∼ 30 and 300 nm for 15‐deoxy‐TIC and 15r‐TIC, respectively, which well correlated with the binding potency for the CNS‐specific PGI2 receptor. 6‐Keto‐PGF1α (a stable metabolite of PGI2), peripheral nervous system‐specific PGI2 ligands and other prostaglandins (PGs) than PGI2 did not show such neuroprotective effects. In vivo, 15r‐TIC protected CA1 pyramidal neurons against ischaemic damage in gerbils. These results indicate that CNS‐specific PGI2 ligands have neuronal survival‐promoting activity both in vitro and in vivo, and may represent a new type of therapeutic drug for neurodegeneration.
Acute inflammatory responses to mechanical lesions in the CNS: differences between brain and spinal cord
Authors: Schnell Lisa , Fearn Sara , Klassen Henry , Schwab Martin E. , Perry V. Hugh
Published: March 2003

Lesion‐induced inflammatory responses in both brain and spinal cord have recently become a topic of active investigation. Using C57BL/6J mice, we compared the tissue reaction in these two central nervous system (CNS) compartments with mechanical lesions of similar size involving both grey and white matter. This evaluation included the quantitative assessment of neutrophils, lymphocytes and activated macrophages/microglia, as well as astrocyte activation, upregulation of vascular cell adhesion molecules (ICAM‐1, VCAM‐1, PECAM) and the extent of blood–brain barrier (BBB) breakdown. Time points analysed post‐lesioning included 1, 2, 4 and 7 days (as well as 10 and 14 days for the BBB). We found clear evidence that the acute inflammatory response to traumatic injury is significantly greater in the spinal cord than in the cerebral cortex. The numbers of both neutrophils and macrophages recruited to the lesion site were significantly higher in the spinal cord than in the brain, and the recruitment of these cells into the surrounding parenchyma was also more widespread in the cord. The area of BBB breakdown was substantially larger in the spinal cord and vascular damage persisted for a longer period. In the brain, as in spinal cord, the area to which neutrophils were recruited correlated well with the area of BBB breakdown. It will be of interest to determine the extent to which the infiltration of inflammatory cells contributes, either directly or indirectly, to the vascular permeability and secondary tissue damage or, conversely, to local tissue repair in the brain and the spinal cord.
Differential expression of the presynaptic cytomatrix protein bassoon among ribbon synapses in the mammalian retina
Authors: Brandstätter Johann Helmut , Fletcher Erica Lucy , Garner Craig Curtis , Gundelfinger Eckart Dieter , Wässle Heinz
Published: March 2003

Bassoon is a 420‐kDa presynaptic protein which is highly concentrated at the active zones of nerve terminals of conventional synapses, both excitatory glutamatergic and inhibitory GABAergic, in rat brain. It is thought to be involved in the organization of the cytomatrix at the site of neurotransmitter release. In the retina, there are two structurally and functionally distinct types of synapses: ribbon and conventional synapses. Antibodies against bassoon were applied to sections of rat and rabbit retina. Strong punctate immunofluorescence was found in the outer and inner plexiform layers. Using pre‐ and post‐embedding immunostaining and electron microscopy, bassoon was localized in the outer plexiform layer at ribbon synapses formed by rods and cones but was absent from basal synaptic contacts formed by cones. In the inner plexiform layer a different picture emerged. As in the brain, bassoon was found at conventional inhibitory GABAergic synapses, made by amacrine cells, but it was absent from the bipolar cell ribbon synapses. These data demonstrate differences in the molecular composition of the presynaptic apparatuses of outer and inner plexiform layer ribbon synapses. Thus, differential equipment with cytomatrix proteins may account for the functional differences observed between the two types of ribbon synapses in the retina.
State‐dependent blockade of haloperidol‐induced sensitization of catalepsy by MK‐801
Authors: Schmidt Werner J. , Tzschentke Thomas M. , Kretschmer Beate D.
Published: March 2003

NMDA receptor antagonists have been shown to block several forms of neural and behavioural plasticity. The prototypical and most widely‐used noncompetitive NMDA receptor antagonist is dizocilpine (MK‐801). Here we have examined the effect of MK‐801 on the context‐dependent augmentation (‘sensitization’) of catalepsy in rats which develops with repeated administration of haloperidol. It was found that over a 7‐day treatment period animals receiving haloperidol (0.25 or 0.5 mg/kg) plus MK‐801 (0.16 mg/kg) showed a context‐dependent day‐to‐day increase in catalepsy similar to animals that received haloperidol alone. However, when all animals were treated with haloperidol alone on day 8 of the experiment, animals that had received haloperidol plus MK‐801 before displayed a much smaller cataleptic response, similar to that observed in the haloperidol group on the first treatment day, i.e. the previously‐established enhancement of catalepsy was no longer expressed. These results may be explained in terms of state‐dependency effects induced by MK‐801. Implications of these findings for the clinical use of NMDA receptor antagonists in the treatment of Parkinson's disease are discussed.
Expression of c‐fos, NGFI‐A and secretogranin II mRNA in brain regions during initiation of cocaine self‐administration in mice
Authors: Kuzmin Alexander , Johansson Björn
Published: March 2003

Intravenous cocaine self‐administration in mice was studied to find correlates of the acquisition of cocaine‐oriented operant behaviour in the expression of nerve growth factor‐induced clone A (NGFI‐A), c‐fos and secretogranin II mRNAs. Yoked control animals, receiving cocaine passively, served as controls for the neurochemical effect of non‐contingent cocaine infusion. Animals controlling their cocaine infusions did more nose‐pokes during a 30‐min trial than yoked controls and animals receiving only saline, indicating a reinforcing effect of cocaine. Compared with saline, an increase in c‐fos mRNA in lateral and basolateral amygdala was found in active cocaine‐receiving animals, and a decrease in yoked controls receiving cocaine. There is previous evidence for an involvement of the amygdala, particularly its basolateral part, in cocaine's effects on motivation. In caudate putamen, both contingent and non‐contingent cocaine increased c‐fos mRNA. Non‐contingent cocaine infusions increased NGFI‐A mRNA expression in the core of nucleus accumbens, medial caudate putamen and frontal cortex, whereas self‐administration eliminated these effects. In the core of the nucleus accumbens and piriform cortex there was increased, and in medial amygdala decreased secretogranin II mRNA in yoked controls compared with saline controls. In contrast, in basomedial and central nuclei of amygdala, increased secretogranin II mRNA was found in self‐administering mice. Previous studies measuring gene expression after cocaine administration obviously did not give the complete picture of changes in gene expression in the drug‐taking organism. As differences in c‐fos and secretogranin II mRNA between active mice and yoked controls were robust, measuring these mRNAs may identify neurons selectively involved in acquisition of cocaine‐taking behaviour.
Inferior olivary‐induced expression of Fos‐like immunoreactivity in the cerebellar nuclei of wild‐type and Lurcher mice
Authors: Oldenbeuving Annemarie W. , Eisenman Leonard M. , De Zeeuw Chris I. , Ruigrok Tom J. H.
Published: March 2003

Earlier behavioural studies have shown that the expression of the immediate‐early gene c‐fos, as visualized by the immunohistochemical detection of Fos, in the inferior olive (IO) correlated closely with expression in related areas of the cerebellar nuclei. It has been speculated that the expression of c‐fos within the cerebellar nuclei may be induced by enhanced spiking activity of the immunopositive neurons in the inferior olive. Two potential mechanisms may play a role in this process: a direct induction by way of the collaterals of the olivary climbing fibres to the cerebellar nuclei, or indirectly, by climbing fibre activity‐induced depression of mossy fibre‐parallel fibre‐induced simple spike frequency of the Purkinje cells resulting in a subsequent disinhibition of the related parts of the cerebellar nuclei. In an attempt to distinguish between these possible mechanisms, we analysed Fos immunoreactivity in the olivocerebellar system of wild‐type mice and in the mutant mouse Lurcher which lacks Purkinje cells. The tremorgenic agent harmaline, which is known to induce enhanced and rhythmic firing of olivary neurons was given intraperitoneally to anaesthetized mice of both genotypes. Harmaline application coincides with the induction of Fos‐immunoreactive neurons in most areas of the IO in both wild‐type and Lurcher mice. Both types of mice also showed enhanced expression in the larger neurons of the cerebellar nuclei. However, in the smaller, GABAergic nucleo‐olivary neurons, increased c‐fos expression was only observed in the wild‐type mice. We conclude that: (i) increased olivary activity indeed may result in increased c‐Fos expression in related areas of the cerebellar nuclei; (ii) because the indirect mode of induction is not operative in Lurcher mice, the olivary collateral innervation of the cerebellar nuclei is sufficient for c‐fos induction in the larger nucleobulbar neurons in Lurcher and potentially also in wild‐type mice; however (iii) for the nucleo‐olivary cells an intact cerebellar cortical input is necessary to evoke increased expression of c‐fos following harmaline application.
Differential projections from the anterior and posterior divisions of the accessory olfactory bulb to the medial amygdala in the opossum, Monodelphis domestica
Authors: Martínez‐Marcos Alino , Halpern Mimi
Published: March 2003

The vomeronasal sensory epithelium of mammals contains apical and basal cell populations expressing different G proteins and putative pheromone receptors, which project, respectively, to the anterior and posterior divisions of the accessory olfactory bulb (AOB). In order to analyse whether these segregated pathways are preserved in the connections between the AOB and the amygdala, conjugated dextran‐amines were iontophoretically injected into the anterior and posterior divisions of the AOB. We found that efferent projections from both divisions essentially overlap throughout the vomeronasal recipient amygdala. In the medial amygdaloid complex, both divisions project to lamina 1A of layer 1 of the anterodorsal, anteroventral, posterodorsal and posteroventral nuclei. The posterior division alone, however, projects to lamina 1B and layers 2 and 3 of the anterodorsal, anteroventral and posteroventral nuclei. These results constitute a link between molecular, anatomical and functional approaches on the study of the vomeronasal system. Molecular and functional studies support that the two segregated pathways between the vomeronasal organ and the AOB are functionally different. Similarly, the anatomical approaches to the further connections of this system indicate that the medial amygdala possesses ventral and dorsal divisions that are hodologically and functionally different. The present results demonstrate a differential projection from the posterior AOB to the ventral division of the medial amygdala. These findings indicate that the segregated pathways of the vomeronasal system continue to the level of the amygdala, and they provide some clues about the functional implications.
FAK+ and PYK2/CAKβ, two related tyrosine kinases highly expressed in the central nervous system: similarities and differences in the expression pattern
Authors: Menegon Andrea , Burgaya Ferran , Baudot Pierre , Dunlap David D. , Girault Jean‐Antoine , Valtorta Flavia
Published: March 2003

Focal adhesion kinase (FAK) and proline‐rich tyrosine kinase 2/cell adhesion kinase β (PYK2/CAKβ) are related, non‐receptor, cytoplasmic tyrosine kinases, highly expressed in the central nervous system (CNS). In addition, FAK+ is a splice isoform of FAK containing a 3‐amino acid insertion in the carboxy‐terminal region. In rat hippocampal slices, FAK+ and PYK2/CAKβ are differentially regulated by neurotransmitters and depolarization. We have studied the regional and cellular distribution of these kinases in adult rat brain and during development. Whereas PYK2/CAKβ expression increased with postnatal age and was maximal in the adult, FAK+ levels were stable. PYK2/CAKβ mRNAs, detected by in situ hybridization, were expressed at low levels in the embryonic brain, and became very abundant in the adult forebrain. Immunocytochemistry of the adult brain showed a widespread neuronal distribution of FAK+ and PYK2/CAKβ immunoreactivities (ir). PYK2/CAKβ appeared to be particularly abundant in the hippocampus. In hippocampal neurons in culture at early stages of development, FAK+ and PYK2/CAKβ were enriched in the perikarya and growth cones. FAK+ extended to the periphery of the growth cones tips, whereas PYK2/CAKβ appeared to be excluded from the lamellipodia. During the establishment of polarity, a proximal‐distal gradient of increasing PYK2/CAKβ‐ir could be observed in the growing axon. In most older neurons, FAK+‐ir was confined to the cell bodies, whereas PYK2/CAKβ‐ir was also present in the processes. In vitro and in vivo, a subpopulation of neurons displayed neurites with intense FAK+‐ir. Thus, FAK+ and PYK2/CAKβ are differentially regulated during development yet they are both abundantly expressed in the adult brain, with distinctive but overlapping distributions.
Retinoic Acid Modulates Gap Junctional Permeability Between Horizontal Cells Of The Mammalian Retina
Authors: Weiler Reto , He Shigang , Vaney David I.
Published: March 2003

In the retina, all‐trans retinoic acid (at‐RA) could function as a light signal because its production increases with the level of illumination. Given the well‐established effects of retinoic acid on cell coupling in other tissues, it is possible that the changing levels of at‐RA modulate the gap junctional permeability between retinal neurons. This study examines the effects of retinoic acid on horizontal cell coupling, which is known to be modulated by the ambient light level. Single horizontal cells were injected under visual control with either Neurobiotin (mouse retina) or Lucifer yellow (rabbit retina) and the extent of tracer coupling or dye coupling was used to monitor the gap junctional permeability. In the mouse retina, the injection of Neurobiotin revealed a network of ≈ 150–250 tracer‐coupled horizontal cells. The tracer coupling was completely abolished by incubating the retina in 150 μm at‐RA for 35 min. In the rabbit retina, the injection of Lucifer yellow into A‐type horizontal cells revealed networks of ≈ 15–30 dye‐coupled horizontal cells. Incubation in 150 μm at‐RA reduced the dye coupling within 12 min and complete uncoupling was achieved after 35 min. The uncoupling effects of at‐RA in the mouse and rabbit retinas were concentration‐ and time‐dependent and they were reversible after washout. The coupling was not affected by either the 9‐cis form of retinoic acid or by at‐RA that had been isomerized by intensive light. The uncoupling effect of at‐RA persisted following treatment with a D1 receptor antagonist and thus was dopamine‐independent. This study has established that at‐RA is able to modulate the gap junctional permeability between horizontal cells in the mammalian retina, where its light‐dependent release has already been demonstrated.
5‐HT1A and 5‐HT1B receptors control the firing of serotoninergic neurons in the dorsal raphe nucleus of the mouse: studies in 5‐HT1B knock‐out mice
Authors: Evrard A. , Laporte A. M. , Chastanet M. , Hen R. , Hamon M. , Adrien J.
Published: March 2003

The characteristics of the spontaneous firing of serotoninergic neurons in the dorsal raphe nucleus and its control by serotonin (5‐hydroxytryptamine, 5‐HT) receptors were investigated in wild‐type and 5‐HT1B knock‐out (5‐HT1B–/–) mice of the 129/Sv strain, anaesthetized with chloral hydrate. In both groups of mice, 5‐HT neurons exhibited a regular activity with an identical firing rate of 0.5–4.5 spikes/s. Intravenous administration of the 5‐HT reuptake inhibitor citalopram or the 5‐HT1A agonist 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT) induced a dose‐dependent inhibition of 5‐HT neuronal firing which could be reversed by the selective 5‐HT1A antagonist N‐[2‐[4‐(2‐methoxyphenyl)‐1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl)cyclohexane carboxamide (WAY 100635). Both strains were equally sensitive to 8‐OH‐DPAT (ED50 ∼ 6.3 μg/kg i.v.), but the mutants were less sensitive than wild‐type animals to citalopram (ED50 = 0.49 ± 0.02 and 0.28 ± 0.01 mg/kg i.v., respectively, P < 0.05). This difference could be reduced by pre‐treatment of wild‐type mice with the 5‐HT1B/1D antagonist 2′‐methyl‐4′‐(5‐methyl‐[1,2,4]oxadiazol‐3‐yl)‐biphenyl‐4‐carboxylic acid [4‐methoxy‐3‐(4‐methyl‐piperazine‐1‐yl)‐phenyl]amide (GR 127935), and might be accounted for by the lack of 5‐HT1B receptors and a higher density of 5‐HT reuptake sites (specifically labelled by [3H]citalopram) in 5‐HT1B–/– mice. In wild‐type but not 5‐HT1B–/– mice, the 5‐HT1B agonists 3‐(1,2,5,6‐tetrahydro‐4‐pyridyl)‐5‐propoxypyrrolo[3,2‐b]pyridine (CP 94253, 3 mg/kg i.v.) and 5‐methoxy‐3‐(1,2,3,6‐tetrahydropyridin‐4‐yl)‐1H‐indole (RU 24969, 0.6 mg/kg i.v.) increased the firing rate of 5‐HT neurons (+22.4 ± 2.8% and +13.7 ± 6.0%, respectively, P < 0.05), and this effect could be prevented by the 5‐HT1B antagonist GR 127935 (1 mg/kg i.v.). Altogether, these data indicate that in the mouse, the firing of 5‐HT neurons in the dorsal raphe nucleus is under both an inhibitory control through 5‐HT1A receptors and an excitatory influence through 5‐HT1B receptors.
Early coding of reaching: frontal and parietal association connections of parieto‐occipital cortex
Authors: Caminiti Roberto , Genovesio Aldo , Marconi Barbara , Mayer Alexandra Battaglia , Onorati Paolo , Ferraina Stefano , Mitsuda Takashi , Giannetti Stefano , Squatrito Salvatore , Maioli Maria Grazia , Molinari Marco
Published: March 2003

The ipsilateral association connections of the cortex of the dorsal part of the rostral bank of the parieto‐occipital sulcus and of the adjoining posterior part of the superior parietal lobule were studied by using different retrograde flourescent tracers. Fluoro‐Ruby, Fast blue and Diamidino yellow were injected into visual area V6A, and dorso‐caudal (PMdc, F2) and dorso‐rostral (PMdr, F7) premotor cortex, respectively. The parietal area of injection had been previously characterized physiologically in behaving monkeys, through a variety of oculomotor and visuomanual tasks. Area V6A is mainly linked by reciprocal projections to parietal areas 7m, MIP (medial intraparietal) and PEa, and, to a lesser extent, to frontal areas PMdr (rostral dorsal premotor cortex, F7) and PMdc (F2). All these areas project to that part of the dorsocaudal premotor cortex that has a direct access to primary motor cortex. V6A is also connected to area F5 and, to a lesser extent, to 7a, ventral (VIP) and lateral (LIP) intraparietal areas. This pattern of association connections may explain the presence of visually‐related and eye‐position signals in premotor cortex, as well as the influence of information concerning arm position and movement direction on V6A neural activity. Area V6A emerges as a potential ‘early’ node of the distributed network underlying visually‐guided reaching. In this network, reciprocal association connections probably impose, through re‐entrant signalling, a recursive property to the operations leading to the composition of eye and hand motor commands.