bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glutamate as the Principal Mossy Fibre Transmitter in Rat Cerebellum: pharmacological evidence
Authors: Garthwaite J. , Brodbelt A. R. 
Published: April 2006

AbstractTo examine the possibility that glutamate may be widely used as the transmitter for cerebellar mossy fibres, population responses of granule cells following electrical stimulation of these fibres were recorded in rat cerebellar slices using a gap technique. Several different vermal lobules (II, V, VIb, VIII, IXc and X) whose main mossy fibre afferents originate in different nuclei, were compared. The mossy fibre response was remarkably similar in appearance in all lobules. With 1.2 mM Mg2+ in the perfusing solution, and with a low rate of stimulation (0.05 Hz), the N‐methyl‐D‐aspartate (NMDA) antagonist, D‐2‐amino‐5‐phosphonovalerate (APV, 30 μM), had little or no effect but all components of the response could be inhibited by the broad spectrum excitatory amino acid antagonist, kynurenate (3 mM), or by the relatively selective non‐NMDA antagonist, 6‐cyano‐2,3‐dihydroxy‐7‐nitro‐quinoxaline (CNQX, 10 μM). Slow APV‐sensitive components emerged during high frequency stimulation (30 ‐ 150 Hz) or, with a low stimulation rate, on removal of Mg2+ or addition of bicuculline (30 μM). The results suggest that an excitatory amino acid, presumably glutamate, is the major mossy fibre transmitter in the cerebellum and that it activates both NMDA and non‐NMDA receptors on granule cells.
Hipppcampal Electrical Activity and Behaviour in Rabbits during Adaptation to a Novel Semi‐Natural Environment
Authors: Fontani Giuliano , Vegni Virginia 
Published: April 2006

AbstractThe aim of the present experiment was to show possible modifications in behaviour and hippocampal electrical activity during adaptation to a novel semi‐natural environment. Rabbits with chronic implanted electrodes in the hippocampus were introduced into a large, natural, open‐air enclosure. Their spontaneous behaviour was studied for 3 days. Electrical activity was recorded by telemetry, stored with behaviour on a video‐tape, and then analysed. Behaviour was divided into categories and variables. The categories were: activity directed towards the environment (including exploratory movements, scanning, marking, etc.) and self‐directed activities (such as eating, drinking, self‐grooming, etc.). Exploratory elements were observed and classified according to a spatial and a temporal criterion. The rabbits showed a progressive adaptation to the environment with quantitative and qualitative reduction in exploration and an increment in quiet immobility and inspective activities. Three EEG patterns were recognized from autocorrelation and spectral analysis: high rhythmicity theta (HRSA) with specific relationship to voluntary movements, such as exploration and running; low rhythmicity theta (LRSA) in signalling activities or self‐directed behaviour and during postural and reactive immobility; and irregular activity (IA) sometimes seen in the same immobile behaviour. The results show that some behaviours (exploration, alert and postural immobility, self‐directed activity) are correlated to specific patterns of electrical activity in the hippocampus and, as exploratory behaviour decreased with time, there was a concomitant increase in EEG frequency.
Organization of the Visual Sector of the Thalamic Reticular Nucleus in Galago
Authors: Conley Michael , Diamond Irving T. 
Published: April 2006

AbstractProjections to and from the visual sector of the thalamic reticular nucleus were studied in the prosimian primate genus Galago by anterograde and retrograde transport of WGA‐HRP injected into the dorsal lateral geniculate nucleus (GLd), pulvinar nucleus, and their cortical targets. Contrary to the idea that thalamic connections with the reticular nucleus are not delimited sharply between nuclei associated with the same modality, our results show a distinct laminar segregation of the projections from the GLd and pulvinar nuclei. The GLd is connected reciprocally with the lateral 2/3 of the caudal part of the reticular nucleus, and the striate cortex sends projections to the same lateral tier. Both sets of projections are organized topographically, lines of projection taking the form of slender elongated strips that run from caudo‐dorsal to rostro‐ventral within the nucleus. The pulvinar nucleus, which projects to several areas of the temporal, parietal, and occipital lobes, including the striate cortex, is connected reciprocally with the medial 1/3 of the caudal part of the reticular nucleus. Every injection into the pulvinar nucleus labelled a wide area of the medial tier, with no indication of visuotopic organization. The projections from the middle temporal area, one of the principal targets of the pulvinar nucleus, also terminate only in the medial tier of the visual sector. And we would expect that, in general, a thalamic nucleus and its cortical target would project to the same part of the reticular nucleus. The case of the striate area is an exception but only in the sense that it projects to the pulvinar nucleus as well as GLd. Thus an injection into a single locus in area 17 produces two parallel strips in the visual sector of the reticular nucleus, but both are in the lateral tier. We propose that each strip arises from a separate population of cells with cortical layer VI, one with an allegiance to the GLd and the other to the pulvinar nucleus.
The Effects of Prenatal Intracranial Infusion of Tetrodotoxin on Naturally Occurring Retinal Ganglion Cell Death and Optic Nerve Ultrastructure
Authors: Friedman S. , Shatz C. J. 
Published: April 2006

AbstractIn the developing vertebrate nervous system, cell death is known to play an important role in determining final neuron number. Retinal ganglion cells in the cat's visual system undergo a massive elimination by cell death during the prenatal period between E44 (age of embryo in days) and birth (=E65). We have examined whether neural activity contributes to ganglion cell death by infusing tetrodotoxin (TTX), a blocker of the voltage‐sensitive sodium channel. TTX was infused intracranially via osmotic minipumps implanted in utero at E42. The effects of the TTX treatment on ganglion cell death and optic nerve ultrastructure were examined at either E49 or E57 by electron microscopy and quantitative analysis of optic axon number. The numbers of optic nerve axons counted in the optic nerves of animals after either 1 or 2 weeks of TTX treatment were not significantly different from the counts in normal animals at comparable ages: E49 TTX—3.2 × 105; E48 normal—3.3 × 105; E57 TTX—2.1 × 105; E59 normal—2.4 × 105. These results suggest that retinal ganglion cells cannot be rescued from death by blockade of neural activity central to the optic chiasma. However, the ultrastructure of optic nerves following 2 weeks of TTX infusion was quite abnormal. The usual packaging of axons into fascicles by glia was disrupted by the presence of many pale, organelle‐poor processes that were about 10 times larger in their cross‐sectional areas than axons in either normal or TTX‐treated nerves. Examination of these processes in serial transverse or in longitudinal electron microscope (EM) sections of the nerve revealed that they were most likely glial in origin. The ultrastructural organization of the optic nerve following 1 week of TTX treatment was normal, indicating that this effect on glial ultrastructure is either cumulative or delayed in onset. These results suggest that while the conduction of action potentials to the terminals of retinogeniculate axons may not play a significant role in regulating ganglion cell number prenatally, it may affect the normal maturation of optic nerve glia.
Protection Against N‐methyl‐D‐aspartate Receptor‐Mediated Neuronal Degeneration In Rat Brain by 7‐chlorokynurenate and 3‐amino‐1‐hydroxypyrrolid‐2‐one, Antagonists at The Allosteric Site for Glycine
Authors: Foster A. C. , Willis C. L. , Tridgett R. 
Published: April 2006

Abstract7‐Chlorokynurenate (7‐Cl KYNA) and 3‐amino‐1‐hydroxypyrrolid‐2‐one (HA‐966), two selective antagonists of the glycine site on the N‐methyl‐D‐aspartate (NMDA) receptor, have been used to assess the involvement of this site in the neurodegeneration resulting from injection of excitotoxins in the rat brain. In the rat striatum, reductions in the enzymes choline acetyltransferase (CAT) and glutamate decarboxylase (GAD), occurring 7 days after a unilateral, intrastriatal injection of quinolinate (200 nmol), were prevented in a dose‐dependent manner by intrastriatal administration of 7‐Cl KYNA (10–50 nmol) and HA‐966 (200–500 nmol) 1 h after the excitotoxin. In the rat hippocampus, degeneration of pyramidal and granule neurons caused by direct injection of quinolinate (60 nmol) was completely prevented by 7‐Cl KYNA (50 nmol) and partially by HA‐966 (500 nmol) injected intrahippocampally 1 h after the excitotoxin. In the rat striatum, 7‐Cl KYNA (50 nmol) and HA‐966 (500 nmol) also reduced neurotoxicity caused by intrastriatal injection of NMDA (200 nmol), but not that caused by the ‘non‐NMDA’ receptor agonists DL‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) or kainate. The time course of protective effects of 7‐Cl KYNA and HA‐966 in the striatum was similar to that previously observed with the uncompetitive NMDA receptor antagonist MK‐801, indicating that activation of the glycine site contributes to the delayed degeneration of neurons which occurs over the first 5 h following quinolinate injection. The neuroprotective effects of both 7‐Cl KYNA and HA‐966 in the rat striatum appear to be mediated via the glycine site on the NMDA receptor as they were completely reversed by D‐serine, but not L‐serine. These results indicate that activation of the glycine site is essential for the expression of the delayed degeneration of neurons resulting from intracerebral injection of an NMDA receptor agonist, a process which bears similarities to the delayed neurodegeneration which results from a period of cerebral ischaemia.
Glutamate Receptors of a Quisqualate‐Kainate Subtype are Involved in the Presynaptic Regulation of Dopamine Release in the Cat Caudate Nucleus in vivo
Authors: Barbeito L. , Chéramy A. , Godeheu G. , Desce J. M. , Glowinski J. 
Published: April 2006

AbstractExperiments were conducted with halothane‐anesthetized cats implanted with a push‐pull cannula in the caudate nucleus in order to estimate the effects of glutamate (GLU) agonists on the release of 3H‐dopamine continuously synthesized from 3H‐tyrosine. In the presence of tetrodotoxin (TTX), glutamate (10−8 M, 10−4 M) and kainate (KAI) (10−5 M) stimulated the release of 3H‐dopamine while quisqualate (10−5 M) and N‐methyl‐D‐aspartate (NMDA) (10−5 M) were without effect. The stimulatory effect of kainate (10−5 M) on 3H‐dopamine release did not seem to be mediated by glutamate released from corticostriatal fibers, as not only kainate, but also quisqualate (QUI) and N‐methyl‐D‐aspartate enhanced the efflux of glutamate through a tetrodotoxin‐resistant process. Riluzole (10−5 M), gamma‐D‐glutamyl‐glycine (GDGG) (10−5 M) and glutamine‐diethyl‐ester (10−5 M) prevented the stimulatory effect of kainate (10−5 M) while 6‐cyano‐7‐nitro‐quinoxaline‐2,3‐dione (CNQX) (10−5 M), kynurenate (10−5 M) and 2‐amino‐5‐phosphonovalerate (APV) (10−5 M) were without effect. In the presence of concanavalin A (CONA) (10−7 M), a lectin which is known to prevent the quisqualate‐evoked desensitization of glutamate receptors, quisqualate (10−5 M) stimulated the release of 3H‐dopamine. In addition, in the absence of concanavalin A, quisqualate (10−5 M) blocked the stimulatory effects of kainate (10−5 M) or glutamate (10−4 M) on 3H‐dopamine release. These results suggest the involvement of receptors of the quisqualate/kainate subtype in the direct glutamate‐induced presynaptic facilitation of dopamine release. In contrast to what was observed in the presence of tetrodotoxin, in the absence of the neurotoxin, high concentrations of glutamate (10−4 M) and kainate (10−5 M) reduced rather than stimulated the release of 3H‐dopamine. A weak inhibitory effect was also observed with quisqualate (10−5 M) while N‐methyl‐D‐aspartate (10−5 M) was without effect. In the light of previous studies, these latter observations suggest that glutamate can also exert an indirect inhibitory presynaptic influence on the release of dopamine from nerve terminals of the nigrostriatal dopaminergic neurons by acting on receptors of the quisqualate/kainate subtype located on striatal GABAergic neurons.
Horizontal Interactions in Cat Striate Cortex: III. Ectopic Receptive Fields and Transient Exuberance of Tangential Interactions
Authors: Luhmann H. J. , Greuel J. M. , Singer W. 
Published: April 2006

AbstractIn this study the developmental changes of intracortical connectivity are related to changes of cortical receptor fields (RFs). The RFs of striate cortex neurons of 4‐ to 8.5‐week‐old kittens, reared under normal conditions (NR) or in a selective visual environment (SE), were analysed quantitatively and compared with adult cats. To unmask weak inputs from outside the conventional RF (CRF), cell excitability was raised by iontophoretic application of glutamate (GLU) and/or bicuculline methiodide (BIC) or by light stimulation of the CRF. Both the dominant discharge region (DDR) and the total RF (TRF) area were significantly larger in NR and SE kittens than in adult cats. Moreover, in kittens 18% of the cells had additional ectopic fields that were excitatory, had similar orientation preferences as the CRF, and ranged 4° to 23° from the centre of the CRF. In 74% of the cases the ectopic fields were direction‐selective and 70% of them preferred stimuli moving toward the CRF. Ectopic fields occurred mainly in supragranular cells, were similarly frequent in simple and complex cells and slightly more frequent in SE (20.7%) than in NR (13.3%) kittens. In adult cats only one of 83 cells tested had an ectopic field. It is concluded that the age‐dependent decrease in the RF size, the laminar distribution of cells having an ectopic RF, and the numerical reduction of these cells with age correlate well with the organization and postnatal pruning of tangential projections, suggesting that these contribute to the elaboration of specific response properties. Moreover, the authors infer from the early presence and from the selectivity of ectopic fields that the system of horizontal intrinsic connections mediates far‐reaching, excitatory interactions between cortical neurons with similar functional properties and serves as a substrate for the processing of global aspects of visual patterns.
Maintenance of Intermediolateral Spinal Cord Neurons by Fibroblast Growth Factor Administered to the Medullectomized Rat Adrenal Gland: Dependence on Intact Adrenal Innervation and Cellular Organization of Implants
Authors: Blottner Dieter , Unsicker Klaus 
Published: April 2006

AbstractWe have previously shown that basic fibroblast growth factor (bFGF; 2 μg), when administered in gelfoams implanted to medullectomized adult rat adrenal glands, maintains target‐deprived preganglionic neurons located in the intermediolateral column (IML) of the spinal cord. We show now that administration of 600 or 60 ng/implant/organ of the biologically active recombinant protein also maintains IML‐neurons. The effects depend on an intact organ nerve supply since administration of bFGF‐implants to the medullectomized and denervated (splanchnicotomized) organ abolishes the maintenance effects for IML‐neurons. A possible regeneration of cholinergic nerve fibres was assessed by quantitative determination of choline acetyltransferase (ChAT)‐activity and ultrastructurally under various treatments. When compared to a cytochrome‐(Cyto)‐C treatment, bFGF significantly increased ChAT‐activity in the innervated adrenal gland after 4 weeks, suggesting that sprouting of cholinergic nerve fibres and/or recovery of enzyme activity had occurred. Electron microscopically, unmyelinated axons associated with Schwann cells were only found in bFGF, but not in Cyto‐C‐implants. We conclude that exogenous bFGF or a yet unidentified trophic molecule possibly induced by bFGF in the adrenal gland acts as a retrogradely transported messenger serving for the maintenance of spinal cord IML‐neurons in vivo. By stimulating axonal sprouting, bFGF might facilitate access of trophic material to nerve fibres.
B‐50/GAP43 Gene Expression in the Rat Olfactory System During Postnatal Development and Aging
Authors: Verhaagen J. , Greer C. A. , Margolis F. L. 
Published: April 2006

AbstractThe olfactory neuroepithelium exhibits neurogenesis throughout adult life, and in response to lesions, a phenomenon that distinguishes this neural tissue from the rest of the mammalian brain. The newly formed primary olfactory neurons elaborate axons into the olfactory bulb. Thus, denervation and subsequent re‐innervation of olfactory bulb neurons may occur throughout life. In this study the authors demonstrate the distribution of the growth‐associated phosphoprotein B‐50/GAP43 and its mRNA in the olfactory neuroepithelium and olfactory bulb during development and aging. In neonatal rats B‐50/GAP43 mRNA was expressed in primary olfactory neurons throughout the olfactory epithelium and in their target neurons in the olfactory bulb, the mitral, juxtaglomerular and tufted cells. In contrast, in adult (7.5 weeks) and aging animals (6–18 months of age) B‐50/GAP43 mRNA expression was progressively restricted to neurons in the basal region of the neuroepithelium and to some of their target mitral and juxtaglomerular cells in the olfactory bulb. The continuing expression of B‐50/GAP43 mRNA in mitral‐ and juxtaglomerular cells in mature animals is thought to be related to their capacity to respond to continuously changing input from the primary olfactory neurons present in the olfactory neuroepithelium.
Synaptic and Nonsynaptic Localization of Benzodiazepine/GABAA Receptor/Cl− Channel Complex Using Monoclonal Antibodies in the Dorsal Lateral Geniculate Nucleus of the Cat
Authors: Soltesz Ivan , Roberts J. David B. , Takagi Hiroshi , Richards J. Grayson , Mohler Hans , Somogyi Peter 
Published: April 2006

AbstractThe two monoclonal antibodies, bd‐17 and bd‐24, are specific for β‐ and α‐subunits of the GABAA/benzodiazepine receptor/chloride channel complex respectively. An abundance of both subunits has been revealed in the visual thalamus of the cat by light microscopic immunocytochemistry using these antibodies. The α‐subunit specific antibody and electron microscopy were used to determine the subcellular distribution of immunoreactivity with respect to specific cell classes in the dorsal lateral geniculate nucleus. Immunoreactivity was always associated with membranes and the degree of immunoreactivity varied greatly between different types of cell as defined by: (i) immunoreactivity for GABA; (ii) soma area; (iii) presence or absence of cytoplasmic laminated bodies (CLB). GABA negative neurons with the smallest soma area showed the strongest immunoreactivity, mainly in the endoplasmic reticulum and also on the somatic plasma membrane. Cytoplasmic laminated bodies could be found in the majority of these neurons. Large GABA negative cells without CLBs were strongly immunoreactive on the plasma membrane of the soma and dendrites, but showed scant if any intracellular immunoreactivity. GABA‐positive cells showed weak intracellular immunoreactivity but negligible if any immunoreactivity at the somatic and proximal dendritic plasma membrane. A similar reaction pattern was found in GABA negative cells which contained no CLBs and which constituted a medium sized cell population. It is suggested that the degree of intracellular receptor immunoreactivity is positively correlated with receptor turnover. The dendrites of projection cells, particularly outside the glomeruli, showed strong immunoreactivity on the plasma membrane. The synaptic junctions formed by many boutons (F terminals) establishing symmetrical synapses with dendrites of relay cells were immunopositive, but no immunoreactivity could be detected at the synapses established by the presynaptic dendrites of the local interneurons. Many axo‐somatic F1 junctions were also immunoreactive. However, immunoreactivity for the receptor/channel complex was also widely distribution on nonsynaptic plasma membranes of somata and dendrites. Thus GABA may act at both synaptic and non‐synaptic sites. Furthermore, the correlation of immunoreactivity for the GABAA receptor complex with previously published properties of physiologically identified cells suggests that the strongly immunoreactive, small, GABA negative cells with CLBs might correspond to the ‘lagged’ X‐type cells, and the large GABA negative receptor outlined cells without CLBs might correspond to some of the Y‐type neurons.
Monoaminergic and Peptidergic Innervation of the Intermedio‐Lateral Horn of the Spinal Cord
Authors: Fuxe K. , Tinner B. , Bjelke B. , Agnati L. F. , Verhofstad A. , Steinbusch H. G. W. , Goldstein M. , Kalia M. 
Published: April 2006

AbstractIn the rat the monoaminergic and neuropeptidergic innervation of the sympathetic visceral nuclei of the entire thoracic spinal cord has been analysed in serial horizontal sections using immunocytochemistry. Tyrosine hydroxylase (TH), Phenyl‐ethanolamine‐N‐methyl‐transferase (PNMT), 5‐hydroxytryptamine (5‐HT), substance P (SP) and enkephalin (ENK) immunoreactive (IR) nerve terminals form tufts of plexa with strong IR in the principal part of the intermediolateral nucleus (ILp) with the terminals in an extraperikaryal location. High densities of these strongly IR terminals are also found in the principal part of the intercalated nucleus (ICp) and in the paraependymal part of the intercalated nucleus (ICpe). The various types of IR nerve terminals also form rostro‐caudally oriented and latero‐medially oriented strands of strongly IR nerve terminals at regular intervals within each segment. Outside these sympathetic nuclei the terminals are absent or only weakly to moderately IR. The similar pattern of monoamine and peptide innervation of the putative preganglionic sympathetic neurons along the entire thoracic spinal cord may be related to the general three dimensional architecture of the preganglionic multipolar neurons. Thus, these inputs tend to cover the entire surface area of the preganglionic neurons in a uniform way. Some heterogeneities have been observed for the TH, PNMT and neuropeptide Y (NPY) innervation which may contribute to a differential control of sympathetic preganglionic neurons. It is suggested that the unique features of the descending monoaminergic or peptidergic neurons to sympathetic spinal nuclei are related to a demand for maintained transmission upon prolonged activation in these cardiovascular systems, allowing the maintenance of cardiovascular homeostasis.