bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

Abstract[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

AbstractThe 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

AbstractBlood 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

AbstractA 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

AbstractIn 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

AbstractAmacrine 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

AbstractSubpopulations 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

AbstractLesions 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

AbstractIn 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.
Effects of GABAergic agonists and antagonists on oscillatory signal propagation in the guinea‐pig accessory olfactory bulb slice revealed by optical recording
Authors: Sugai Tokio , Sugitani Michio , Onoda Norihiko 
Published: March 2003

AbstractTo investigate the action of GABAergic agents on oscillatory signal propagation induced by electrical stimulation of the vomeronasal nerve layer, optical and electrophysiological recordings were carried out in slice preparations of the guinea‐pig accessory olfactory bulb. In response to electrical stimuli, characteristic optical signals appeared in each layer: in the vomeronasal nerve layer, a transient presynaptic response; in the glomerular layer, pre‐ and postsynaptic responses; in the external plexiform, mitral cell and granule cell layers, a damped oscillatory response. Application of the GABAergic agonists, that is, GABA, muscimol (a GABAA receptor agonist) and baclofen (a GABAB receptor agonist), suggested that the GABAB action existed mainly in the glomeruli, whereas the GABAA action was present in both the glomeruli and the external plexiform layer. Bicuculline (a GABAA receptor antagonist) produced long‐lasting but nonoscillating excitation in the external plexiform and mitral cell layers, indicating that the GABAA action contributes to the formation of oscillatory responses. When double‐pulse stimulation was applied to the vomeronasal nerve layer, the test responses in the glomerular layer and external plexiform and mitral cell layers were depressed, but those in the vomeronasal nerve layer were not. Application of 2‐hydroxysaclofen (a GABAB receptor antagonist) mostly blocked paired‐pulse depression occurring in the glomerular layer and restored the reduced transmission to mitral cells, but had only a small effect on the depressed oscillatory response in the external plexiform and mitral cell layers. These observations suggest that GABAB action in the glomerular layer might, at least, regulate information flow from vomeronasal afferents to apical dendrites of mitral cells, like a gate inhibition. However, actions other than GABAB could also be involved in the depression of the oscillation in the external plexiform and mitral cell layers.
The pH response of rat cutaneous nociceptors correlates with extracellular [Na+] and is increased under amiloride
Authors: Steen Kay H. , Wegner Holger , Reeh Peter W. 
Published: March 2003

AbstractExcess hydrogen ions induce sustained nociceptor excitation as well as pain, and this has been suggested, with evidence from sensory ganglion cells, to result from gating a slowly inactivating sodium/calcium inward current. In the rat skin‐nerve preparation, isolated receptive fields of pH‐sensitive C‐fibre terminals were exposed to low‐pH solutions of various sodium concentrations. The pH responses showed a good correlation with log [Na+]e, which supports the above model. Amiloride has previously been shown to block a pH‐induced Na+ current involved in sensory transduction in hamster taste cells; however, it has been shown to act differently in cutaneous nociceptors. Amiloride induced a dose‐dependent increase in and prolongation of the nociceptive pH responses, with a prominent acceleration of the onset. The latter could be mimicked by replacing external sodium with sucrose, thus impeding sodium‐proton antiport. Together, the findings indicate functional expression of amiloride‐sensitive Na+/H+‐antiporters, which enable the nociceptive nerve endings to extrude invading H+. Intracellular acidification may thus compete with Na+/H+ exchange, and pHi may be decisive in the transduction of nociception and pain from tissue acidosis.