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  • 1
    Electronic Resource
    Electronic Resource
    Modulation of sensory inhibition in the ventrobasal thalamus via activation of group II metabotropic glutamate receptors by 2R,4R-aminopyrrolidine-2,4-dicarboxylate (1998)
    Springer
    Experimental brain research 121 (1998), S. 181-185 
    Details
    ISSN: 1432-1106
    Keywords: Key words Metabotropic glutamate receptors ; 2R ; 4R-4-Aminopyrrolidine-2 ; 4-dicarboxylate ; Somatosensory thalamus ; Presynaptic inhibition ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Recordings were made from single neurones responsive to somatosensory input in the ventrobasal thalamus of the anaesthetised rat. GABAergic afferent inhibition arising from the thalamic reticular nucleus was evoked using a condition-test vibrissal stimulation paradigm. Local iontophoretic application of the group II metabotropic glutamate receptor (mGluR) agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the vicinity of the recorded neurones produced a reduction of the afferent inhibition (from 78±3.0% to 25±5.3%), presumably via a presynaptic mechanism. This effect could be antagonised by LY307452, a known group II mGluR antagonist. In contrast, two selective group I mGluR agonists, (S)-3,5-dihydroxyphenylglycine (DHPG) and trans-azetidine-2,4-dicarboxylate (tADA), were without effect on the GABAergic inhibition. These data show that group II but not group I mGluRs can have a significant role in the modulation of GABAergic afferent inhibition in the ventrobasal thalamus. This could be of importance in the control of sensory discriminative processes and functions of sleep, arousal and seizure generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050450
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  • 2
    Electronic Resource
    Electronic Resource
    Developmental changes in NMDA receptor-mediated visual activity in the rat superior colliculus, and the effect of dark rearing (1998)
    Springer
    Experimental brain research 120 (1998), S. 335-344 
    Details
    ISSN: 1432-1106
    Keywords: Key words Plasticity ; Glutamate ; AP5 ; Visual Deprivation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  N-methyl-D-aspartate (NMDA) receptor-mediated activity is considered important for experience-dependent plasticity in the developing visual system. We investigated the influence of age and experience on the role of NMDA receptors in the visual transmission in the superficial grey layer of the superior colliculus (SGS) of the superior colliculus, where, in the adult, NMDA receptors mediate a substantial part of the visual response. In normally reared (postnatal day 14, P14, to adult) rats, visual responses were challenged with NMDA receptor-selective iontophoretic applications of the antagonist D-2-amino-5-phosphonovalerate (AP5). After eye opening (at P14), there was a significant increase in the number of neurones whose visual responses were reduced during AP5 ejection, which peaked at P22 (85%; n = 21), and then declined to adult levels (66%; n = 47) at P25. The mean reduction of the response (from control levels) by AP5 was similar at all ages (approximately 40%). Dark rearing had striking effects on the role of NMDA receptors in visual transmission, especially when comparisons were made between age-matched subjects greater than P25. In these subjects, AP5 ejection reduced the visual responses of all neurones studied. In addition, AP5 ejection caused a significantly larger reduction of visual responses in dark-reared rats (mean reduction 62 ± 4; n = 29) compared with age-matched controls (mean reduction 44 ± 8; n = 23). The D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) reduced the visual responses of every neurone studied and there were no age- or experience-dependent effects. We conclude that NMDA receptors, but not AMPA receptors, assume greater importance for visual transmission in the SGS of dark-reared rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050407
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  • 3
    Electronic Resource
    Electronic Resource
    Retinal repair by transplantation of photoreceptor precursors (2006)
    [s.l.] : Nature Publishing Group
    Nature 444 (2006), S. 203-207 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Photoreceptor loss causes irreversible blindness in many retinal diseases. Repair of such damage by cell transplantation is one of the most feasible types of central nervous system repair; photoreceptor degeneration initially leaves the inner retinal circuitry intact and new photoreceptors ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05161
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  • 4
    Electronic Resource
    Electronic Resource
    Mediation of Thalamic Sensory Responses In Vivo by ACPD-activated Excitatory Amino Acid Receptors (1993)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 5 (1993), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The existence of the so-called metabotropic excitatory amino acid receptor has been known for some years. Various functions have been suggested for this receptor, but the lack of selective antagonists for (IS, 3R)-aminocyclopentane dicarboxylic acid (ACPD) has precluded the direct demonstration of a functional role for this receptor in synaptic processes. We describe here a specific antagonism of the excitatory responses of thalamic neurons to ACPD by two novel antagonists, and a parallel antagonism by these compounds of sensory synaptic responses to noxious stimuli of the same neurons. This provides the first direct pharmacological evidence for a functional role of ACPD-sensitive receptors in central neurotransmission, and indicates that these receptors may play an important part in central sensory processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1993.tb00484.x
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  • 5
    Electronic Resource
    Electronic Resource
    Excitatory Actions of the Metabotropic Excitatory Amino Acid Receptor Agonist, trans-(±)-1-amino-cyclopentane-1,3-dicarboxylate (t-ACPD), on Rat Thalamic Neurons In Vivo (1991)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 3 (1991), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The metabotropic excitatory amino acid receptor agonist trans-(±)-1-amino-cyclopentane-1,3-dicarboxylate (t-ACPD) was applied to rat ventrobasal thalamic neurons by iontophoresis. This agonist typically evoked an excitatory response which was slower in onset and of longer duration than responses to the other excitatory amino acid agonists, N-methyl-aspartate, kainate or (R.S)-a-amino-3-hydroxy-5-methyl-4-isoxazolepropionate. Responses to f-ACPD were resistant to the excitatory amino acid antagonists 6-cyano-7-nitroquinoxaline-2,3-dione, 3-((RS)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid and kynurenate. These results suggest that f-ACPD may exert its effects via the so-called ‘metabotropic’ excitatory amino acid receptor. The putative antagonists at this receptor, D-2-amino-4-phosphono-butyrate (D-AP4), L-2-amino-4-phosphono-butyrate (L-AP4) and L-2-amino-3-phosphono-propionate (L-AP3), were able to reduce responses to t-ACPD under certain circumstances. However, such antagonism was always accompanied by similar reductions in excitatory responses to other agonists. These non-selective effects would appear to limit the usefulness of AP4 and AP3 as antagonists of t-ACPD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1991.tb00045.x
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  • 6
    Electronic Resource
    Electronic Resource
    Sensory Excitatory Postsynaptic Potentials Mediated by NMDA and non-NMDA Receptors in the Thalamus in vivo (1991)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 3 (1991), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Excitatory amino acid neurotransmitters, such as l-glutamate, act at several receptors in the brain, which are sometimes referred to as N-methyl-d-aspartate (NMDA) and non-NMDA receptors. Extensive in vitro work indicates that both NMDA receptors and non-NMDA receptors contribute to excitatory postsynaptic potentials (epsps). The contribution of NMDA receptors to epsps in vivo under physiological conditions is, however, almost unknown. The receptors that mediate the epsps evoked in thalamic relay cells by natural stimulation of sensory afferents have been investigated in anaesthetized rats, and we report the first pharmacological characterization of an excitatory amino acid receptor-mediated epsp in vivo involving both non-NMDA receptors and, in particular, NMDA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1991.tb00092.x
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  • 7
    Electronic Resource
    Electronic Resource
    Excitatory Amino Acid Receptors Participate in Synaptic Transmission of Visual Responses in the Superficial Layers of the Cat Superior Colliculus (1994)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 6 (1994), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The contribution of NMDA and non-NMDA receptors to visual synaptic transmission in the superficial layers of the superior colliculus of the cat has been studied using extracellular recording and iontophoretic techniques. Neuronal responses to natural visual stimulation and the ejection of NMDA and AMPA were observed in the absence and presence of the antagonists CNQX, CPP and AP5. CNQX routinely reduced the responses to visual stimulation at ejection currents which selectively blocked the responses to AMPA but not those to NMDA. Agonist selective ejection currents of CPP and AP5 also reduced visual responses of most SC neurons, but there was a substantial majority whose visual responses were resistant to these antagonists. Neurons with CPP/AP5 resistant visual responses were more commonly found 750–1000 μm from the dorsal surface of the SC. The data indicate that, while non-NMDA receptors are heavily involved in visual synaptic transmission in the superficial SC, the involvement of NMDA receptors varies with recording depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1994.tb00257.x
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  • 8
    Electronic Resource
    Electronic Resource
    Visual experience alters the molecular profile of NMDA-receptor-mediated sensory transmission (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: N-methyl-d-aspartate (NMDA) receptors (NMDArs) may facilitate experience-dependent changes in the visual system. Early sensory experience has an influence over the production of the molecular components from which NMDArs are assembled, and thereby alters the properties of functional receptors. Using the antagonists d-2-amino-5-phosphonovalerate (AP5) and 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP), which have some selectivity for different variants of the NMDAr, we demonstrate that visual deprivation (by dark rearing) has functional consequences for NMDArs in the superior colliculus. An increase in the sensitivity of visual responses to AP5 in dark-reared rats indicated that NMDArs were more important for visual transmission in these individuals. We also observed a relative change in the efficacy of the antagonists against the visual responses of normal versus dark-reared rats. AP5 reduced the visual responses of both groups, but CPP was ineffective against visual responses after dark rearing. In the same neurons, CPP blocked NMDA induced activity indicating that molecular adaptations of NMDArs are specific to those synapses mediating visual activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1999.00544.x
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  • 9
    Electronic Resource
    Electronic Resource
    Novel mode of nitric oxide neurotransmission mediated via S-nitroso-cysteinyl-glycine (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: S-nitroso-cysteinyl-glycine, a novel nitric oxide-adduct thiol compound, can be detected in the brain (2.3 ± 0.6 pmol/mg protein), and released following stimulation of sensory afferents to the rat ventrobasal thalamus in vivo (resting conditions 17 n m; stimulation: 186 n m). Iontophoretic application of CysNOGly (20–80 nA) onto thalamic neurons in vivo resulted in enhancements of excitatory responses to either NMDA or AMPA (182 ± 13.6% and 244 ± 27.8% of control values, n = 15). CysNOGly enhanced responses to stimulation of vibrissal afferents to 132 ± 2.2% (n = 7) of control values. In contrast, the dipeptide CysGly reduced responses of ventrobasal neurons to NMDA and AMPA (54 ± 8.4% and 55 ± 10.8% of control, n = 5). CysNOGly was also a potent activator of soluble guanylate cyclase in vitro. Moreover, we found that NMDA elevated CysNOGly levels in vitro and this stimulatory effect was reduced by inhibitors of the neuronal NO synthase and of the γ-glutamyl transpeptidase, suggesting that production of NO and CysGly is a prelude to CysNOGly synthesis. These findings suggest that the nitrosothiol CysNOGly plays a role in synaptic transmission in the ventrobasal thalamus. We propose a novel synaptic buffering mechanism where S-nitroso-cysteinyl-glycine serves to restrict the locus of action of nitric oxide and so increase its local availability for target delivery. This could lead to a change in neuronal responses favouring sensory transmission similar to that seen in wakefulness or arousal in order to locally enhance transmission of persistent sensory stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00285.x
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  • 10
    Electronic Resource
    Electronic Resource
    Physiological role of group III metabotropic glutamate receptors in visually responsive neurons of the rat superficial superior colliculus (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: There is evidence from immunohistochemical and in situ hybridization studies for the presence of Group I, II and III metabotropic glutamate receptors (mGluRs) in the rat superficial superior colliculus (SSC). The purpose of this study was to investigate if manipulation of Group III mGluRs affects visual responses in the SSC. Drugs were applied by iontophoresis and single neuron activity was recorded extracellularly. L-AP4 (Group III agonist) resulted in a reduction of visual responses in most neurons, but also a potentiation in others. The effect of L-AP4 is drug- and stereospecific in that application of D-AP4 did not significantly affect visual responses. L-AP4 application also resulted in a potentiation of the response to iontophoretically applied NMDA. The effects of MPPG and CPPG (Group III antagonists) were compared with the effect of L-AP4 in the same neuron and were found to produce the opposite effect to L-AP4. Furthermore, the effect of L-AP4 could be blocked by coapplication of MPPG or CPPG. Presynaptic depression of glutamate release is a possible mechanism by which L-AP4 could reduce visual responses in the SSC whereas the potentiation of visual responses by L-AP4 could be due to a reduction of GABAergic inhibition. The finding that MPPG and CPPG, as well as antagonizing the L-AP4 effect, have a direct effect on visual responses suggests that Group III mGluRs are activated by endogenous transmitter released during visual stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00972.x
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