Glutamate-induced ionic currents in cultured neurons from the rat superior colliculus (original) (raw)
Related papers
The Journal of neuroscience, 1989
The aim of the present study was to identify and characterize the receptors and ionic channels mediating the compound response of tectal neurons to exogenous L-glutamate (Glu). Particular attention was paid to the question of whether separate receptors and channels exist for quisqualate (QA) and kainate (KA) and, if so, whether binding to one of these receptors would modify the response elicited through the other. Neurons were dissociated from the superficial gray layer of the superior colliculus from E21 or Pl rats. Between days 14 and 21 in vitro, responsiveness of tectal neurons to Glu and related substances was tested by recording the wholecell currents induced by rapid superfusion with drug-containing salt solutions. Our experiments showed that tectal neurons express at least 3 distinct types of receptors for acidic amino acids. KA-activated currents (I,,,,) differ from QA-activated currents (I,,,,) in their dose-response characteristics, desensitization patterns, selective blockade with kynurenic acid and suppression by elevated [Ca2+lW IcKAj, but not &, is significantly reduced by low levels of [Clt],, and the [CIt],-dependent shift of the reversal potential for ItKI) suggests that KA promotes a conductance decrease for Cl-. Such an effect has been ascribed to APB-receptors, but L-2-amino-4-phosphonobutyrate (APB) itself failed to induce current responses in tectal neurons. KA was without effect when administered together, and in equimolar concentrations, with QA. The block of kK,,) was, however, surmounted by applying KA at considerably higher concentrations. It is concluded that QA acts as a low-affinity competitive antagonist at the KA site and as a high-affinity agonist at its own receptor. The response to the endogenous ligand Glu reflects properties of all receptors. QA and KA receptors account for 20-30% (QA) and 49-82% (KA) of the compound current elicited with 100 PM Glu. These results indicate that binding of Glu does not, in contrast to QA, produce any significant suppression of the KA-receptor-mediated current component. The density of binding sites for L-glutamate (Glu) is known to be high in the superficial gray layer of the mammalian superior colliculus (SC) (Greenamyre et al., 1984; Monaghan and Cot
Title Evidence for glutamate as a neuroglial transmitter withinsensory ganglia
2013
This study examines key elements of glutamatergic transmission within sensory ganglia of the rat. We show that the soma of primary sensory neurons release glutamate when depolarized. Using acute dissociated mixed neuronal/glia cultures of dorsal root ganglia (DRG) or trigeminal ganglia and a colorimetric assay, we show that when glutamate uptake by satellite glial cells (SGCs) is inhibited, KCl stimulation leads to simultaneous increase of glutamate in the culture medium. With calcium imaging we see that the soma of primary sensory neurons and SGCs respond to AMPA, NMDA, kainate and mGluR agonists, and selective antagonists block this response. Using whole cell patch-clamp technique, inward currents were recorded from small diameter (,30 mm) DRG neurons from intact DRGs (ex-vivo whole ganglion preparation) in response to local application of the above glutamate receptor agonists. Following a chronic constriction injury (CCI) of either the inferior orbital nerve or the sciatic nerve,...
Neuroscience, 1995
We have investigated the pattern of glutamate-like immunoreactivity in the superficial layers of the rat superior colliculus by means of postembedding immunocytochemical methods for light and electron microscopy. At the light microscopic level, labelling was faintly to moderately intense in most perikarya of the stratum zonale, stratum griseum superficiale and stratum opticum. Furthermore, strong glutamate-immunoreactive terminal-like elements were accumulated most densely in stratum zonale, stratum griseum superficiale and stratum opticum. At the electron microscopic level, a postembedding immunogold method revealed that the vast majority of those labelled elements corresponded to retinal and visual cortical terminals. These profiles were about twice as heavily labelled as their postsynaptic partners. To determine the contribution of retinal and cortical afferents to the pattern of glutamate-like immunoreactivity, rats were subjected to right retinal ablation, left cortical ablation or combined right retinal and left cortical ablations. After retinal ablation, strongly labelled perikarya were observed in the retinorecipient layers. Furthermore, a prominent loss of glutamate-immunoreactive terminal-like elements occurred in stratum zonale and stratum griseum superficiale. Ipsilateral superior colliculus to cortical ablation exhibited subtle changes characterized by a moderate increase in perikaryal immunostaining in stratum zonale, stratum griseum superficiale and stratum opticum and by an apparent discrete reduction of labelled dots in stratum griseum superficiale and stratum opticum. In cases with combined lesions, strongly immunoreactive cell bodies and dendrites were accompanied by a massive disappearance of labelled terminal-like elements in stratum zonale, stratum griseum superficiale and stratum opticum. The effect of retinal and visual cortical ablations on the pattern of glutamate-like immunoreactivity suggests that these afferents are the major sources for glutamate-immunoreactive terminals in the rat superior colliculus. In addition, these findings provide further evidence for glutamate as neurotransmitter in the visual pathways studied.
Structural requirements for the inhibition for L-glutamate uptake by glia and nerve endings
Brain Research, 1975
There is good evidence that L-glutamate may be an important excitatory transmitter at many sites in the CNSa and it has been suggested that, in common with other amino acid neurotransmitter candidates, its synaptic actions may be terminated by reuptake into a specific transmitter pool within nerve terminals 22. Although isolated nerve ending fractions will accumulate glutamate by a high-affinity transport process 15, other biochemical evidencel,4,~7, 2a suggests that uptake into glial cells may be of greater significance in terminating transmitter action and indeed glial cells have recently been found to accumulate glutamate by a high-affinity system 1°,~.
Neurochemistry International, 1997
The characteristics of high-K+ and electricallyevokedendogenousglutamate and [3H]D-aspartate release have been studied in multiple in oitrw preparations of the rat hippocampus(transverse slices, granulecellscultures, synaptosomesand mossyfibresynaptosomes)under similarexperimentalconditions. High external K+ concentrations evoked [3H]D-aspartateand endogenousglutamate overflowin a concentration-dependent manner in all preparations (except it was not possible to measure endogenous glutamate outflow from granule celk). This effect was tetrodotoxin-insensitivebut partially calciumdependent. In slices,field electrical stimulation evoked an overtlowof endogenousglutamate, but not of [3H]D-aspartate,in a frequency-dependentmanner. This effect was concentration-dependentlyamplified bytheglutamate uptake inhibitorL-trans-pyrrolidine-2,4-dicarboxylic acid (t-PDC).The electricallyevoked glutamate overtlowin the presenceof t-PDCwas tetrodotoxin-sensitiveandcalcium-dependent.In primary dentate gyrus cell cultures, electrical stimulation evoked an overtlowof [3H]D-aspartatein a frequencydependentmanner, whileendogenousglutamate outflowwas not detectable. This effectcould be inhibited by tetrodotoxin and by the N-type calcium channel blocker ro-conotoxinGVIA. Finally, the effect of adenosine has been studied in order to assess the pharmacologicalmodulability of [3H]D-aspartate and endogenous glutamate stimulation-inducedoverflow.Adenosine was found to inhibit 35mM K+-and 20Hz electrical stimulation-induced[3H]D-aspartateand endogenousglutamate overflow.These effects were all prevented by the Al receptor antagonist 8-cyclopentyl-l,3 dimethylxanthine (CPT). These data are in line with the hypothesisthat reuptake plays a role in regulating glutamate release, and that [3H]Daspartate represents a valid marker of endogenous glutamate under most (but not all) experimental conditions. Q 1997ElsevierScienceLtd 113
Glutamate-Induced Inhibition of D-Aspartate Uptake in Müller Glia from the Retina
Neurochemical Research, 2000
Müller glial cells from the retina "in situ" and in primary culture, mainly express the high-affinity sodium-coupled glutamate/aspartate transporter GLAST-1, which dominates total retinal glutamate (Glu) uptake, suggesting a major role for these cells in the modulation of excitatory transmission. The possible involvement of ionotropic and metabotropic Glu receptors in the regulation of Glu uptake was studied in primary cultures of Müller glia. We demonstrate that exposure to 1 mM L-Glu induces a time-dependent inhibition of D-aspartate (D-Asp) uptake in a Na ϩ -dependent manner, as a result of a reduction in the number of transporters at the plasma membrane. The inhibition of D-Asp uptake by Glu was not mimicked by agonists or modified by antagonists of ionotropic and metabotropic Glu receptors. In contrast, transport was inhibited by GLAST-1 transportable substrates threo-hydroxyaspartate and aspartate--hydroxamate, but not by the nontransportable inhibitors trans-pyrrolidine dicarboxylate or DL-threo--benzyloxyaspartic acid. Under the same experimental conditions, L-Glu did not affect the sodium-dependent transport systems for glycine or GABA. The present results demonstrate that the specific downregulation of glutamate/aspartate transport by L-Glu is unrelated to Glu receptor activation, and results from the internalization of transporter proteins triggered by the transport process itself. Such negative feedback of Glu on Glu transport, could contribute to retinal toxicity under pathological conditions in which high extracellular concentrations of Glu are reached.
Brain Research Bulletin, 1983
NIEOULLON, A. AND N. DUSTICIER. Glutamate uptake, glutamate decarboxylase and choline acetyltransferase in subcortical areas after sensorimotor cortical ablations in the cat. BRAIN RES BULL lO(3) 287-293, 1983.-High affinity glutamate uptake (HAGU), glutamate decarboxylase (GAD) and choline acetyltransferase (CAT) activities were measured from subcortical nuclei in the cat brain after ipsilateral ablation of the sensorimotor cortex. Results showed a drop in HAGU in all the structures assayed except the subthalamic nucleus. These changes in HAGU are generally accompanied by a decrease in GAD while CAT is unaffected. However, in the red nucleus the drop in HAGU is concomitant to an increase in GAD and CAT. In the subthalamic nucleus HAGU and CAT are increased while GAD is decreased. These results are consistent with the concept that most corticofugal tibres to subcortical structures use glutamate as their neurotransmitter. Results concerning GAD suggest that GABAergic subcortical neurons are under a cortical influence. This influence seems to be weak on cholinergic neurons. Glutamate uptake Glutamate decarboxylase Choline acetyltransferase Cortical lesion THE cerebral cortex exerts a facilitatory action on subcortical structures involved in sensorimotor integration. 'lhe authors are grateful to Lydia Krrherian for her r\cellenl contribution to experiments on glutamate uptake and to Dr. C. Palmer who kindly revised the English form of the manuscript. 'l'hi, work was supported hy grants from INSERM (contrat lihre no. 81.60.20).
Evidence for Glutamate as a Neuroglial Transmitter within Sensory Ganglia
PLoS ONE, 2013
This study examines key elements of glutamatergic transmission within sensory ganglia of the rat. We show that the soma of primary sensory neurons release glutamate when depolarized. Using acute dissociated mixed neuronal/glia cultures of dorsal root ganglia (DRG) or trigeminal ganglia and a colorimetric assay, we show that when glutamate uptake by satellite glial cells (SGCs) is inhibited, KCl stimulation leads to simultaneous increase of glutamate in the culture medium. With calcium imaging we see that the soma of primary sensory neurons and SGCs respond to AMPA, NMDA, kainate and mGluR agonists, and selective antagonists block this response. Using whole cell patch-clamp technique, inward currents were recorded from small diameter (,30 mm) DRG neurons from intact DRGs (ex-vivo whole ganglion preparation) in response to local application of the above glutamate receptor agonists. Following a chronic constriction injury (CCI) of either the inferior orbital nerve or the sciatic nerve, glutamate expression increases in the trigeminal ganglia and DRG respectively. This increase occurs in neurons of all diameters and is present in the somata of neurons with injured axons as well as in somata of neighboring uninjured neurons. These data provides additional evidence that glutamate can be released within the sensory ganglion, and that the somata of primary sensory neurons as well as SGCs express functional glutamate receptors at their surface. These findings, together with our previous gene knockdown data, suggest that glutamatergic transmission within the ganglion could impact nociceptive threshold.