On the activity of ?-aminobutyric acid and glutamate transporters in chick embryonic neurons and rat synaptosomes

Lewin, Lena; Mattsson, Mats Olof; Rassin, David K.; Sellström, Åke

doi:10.1007/bf00974574

Cited by 9 publications

(3 citation statements)

References 19 publications

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“…1, C and D, shows that the increase in transport following extracellular GABA treatment is both concentration-dependent and time-dependent. A logistic fit to the concentrationresponse data estimates an EC 50 for up-regulation by GABA to be approximately 5 M, which is comparable to the K m values for GABA uptake in both brain tissue (27,28) and in cells heterologously expressing GAT1 (23,26,29). Additionally, maximal up-regulation of uptake occurred with 30 min of pretreatment with 100 M GABA.…”

Section: Resultssupporting

confidence: 53%

Regulation of γ-Aminobutyric Acid (GABA) Transporters by Extracellular GABA

Bernstein

Quick

1999

Journal of Biological Chemistry

155

100

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␥-Aminobutyric acid (GABA) transporters on neurons and glia at or near the synapse function to remove GABA from the synaptic cleft. Recent evidence suggests that GABA transporter function can be regulated, although the initial triggers for such regulation are not known. One hypothesis is that transporter function is modulated by extracellular GABA concentration, thus providing a feedback mechanism for the control of neurotransmitter levels at the synapse. To test this hypothesis, GABA uptake assays were performed on primary dissociated rat hippocampal cultures that endogenously express GABA transporters and on mammalian cells stably expressing the cloned rat brain GABA transporter GAT1. In both experimental systems, extracellular GABA induces chronic changes in GABA transport that occur in a dose-dependent and time-dependent manner. In addition to GABA, ACHC and nipecotic acid, both substrates of GAT1, up-regulate transport; GAT1 transport inhibitors that are not transporter substrates down-regulate transport. These changes occur in the presence of blockers of both GABA A and GABA B receptors, occur in the presence of protein synthesis inhibitors, and are not influenced by intracellular GABA. Surface biotinylation experiments reveal that the increase in transport is correlated with an increase in surface transporter expression. This increase in surface expression is due, at least in part, to a slowing of GAT1 internalization in the presence of extracellular GABA. These data suggest that the GABA transporter fine-tunes its function in response to extracellular GABA and would act to maintain a constant level of neurotransmitter at the synaptic cleft. GABA1 transporters are members of a large family of Na ϩ -dependent neurotransmitter reuptake proteins, located on the plasma membrane of neurons and glia, that function in part to determine neurotransmitter levels in the synaptic cleft (1). Demonstration of a physiological role for GABA transporters comes from experiments involving specific GABA uptake inhibitors; these inhibitors prolong the decay phase of GABA A receptor-mediated post-synaptic potentials (2) and both prolong the decay phase and increase the magnitude of responses mediated by the G protein-coupled GABA B receptor (2-4). GABA transporters also play a physiological role in toad and catfish horizontal cells where calcium-independent GABA efflux through the transporter is a principal mode of neurotransmitter release (5). GABA transporters also have a pathophysiological role. There is decreased calcium-independent GABA release in the affected hippocampus of temporal lobe epileptics. This decrease in transporter-mediated efflux is correlated with fewer GABA transporters and is hypothesized to result in decreased inhibitory tone (6).Not only can GABA transporters regulate neuronal signaling, transport itself can be regulated. This is true for GABA transporters and other members of this family as well (for review see Refs. 7 and 8). Functional modulation occurs through a variety of second messengers such as...

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Section: Resultssupporting

confidence: 53%

Regulation of γ-Aminobutyric Acid (GABA) Transporters by Extracellular GABA

Bernstein

Quick

1999

Journal of Biological Chemistry

155

100

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“…In the case of GABA, in which ''high-affinity'' transport is located predominantly in neurons, it is actually expressed more strongly in the developing, as compared to the adult, nervous tissue (for a review, see Balcar and Johnston, 1987). Developmental time course of EAA transport in nervous tissue has not been studied in the same detail as that of GABA transport (except in culture: Yu et al, 1984;Lewin et al, 1992), but it has been demonstrated that [ 3 H]L-glutamate is strongly accumulated by neuronal perikarya well before the formation of most of the excitatory synapses, at least in the rat hippocampus (Schmidt and Wolf, 1988). Since, in the adult hippocampus, glutamate transporters are located predominantly in glial cells (Rothstein et al, 1994;Lehre et al, 1995) those findings (Schmidt and Wolf, 1988) suggest a specific role 1 antibody (B), showing co-localisation between the neuronal marker NF200, and the glutamate transporter GLT-1.…”

Section: Discussionmentioning

confidence: 99%

Glutamate transport in cultures from developing avian cerebellum: Presence of GLT-1 immunoreactivity in Purkinje neurons

Meaney¹,

Balcar²,

Rothstein³

et al. 1998

J. Neurosci. Res.

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Immunocytochemical studies indicated that Purkinje cells cultured from chick embryonic cerebellum (embryonic day 8) strongly express a glutamate transporter EAAT2 cloned from human brain (GLT-1 in rat brain). At both 7 days and 14 days in culture, Purkinje neurons accumulated 1 microM [3H]L-glutamate via a potent "high-affinity" transport system that could be inhibited by D- and L-threo-3-hydroxyaspartate (D- and L-t-3OHA) and by L-trans-pyrrolidine-2,4-dicarboxylate (L-t-PDC). The order of potency of the three inhibitors was L-t-PDC approximately L-t-3OHA > D-t-30HA. Only the value of IC50 (concentration causing 50% inhibition) for D-t-3OHA significantly changed between 7 days (116 microM) and 14 days in culture (40 microM). All nH approximately 1, except in the case of the inhibition by D-t-3OHA at 14 days in culture (nH = 0.57), indicating the possible appearance of heterogeneity of the transport sites at later stages of culturing. Chronic inhibition of L-glutamate transport by L-t-PDC resulted in major changes in the morphology of Purkinje cells; particularly, the neurites almost completely regressed.

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“…In a previous paper we studied the effect of SKF 89976-A on the ['HIGABA release from 6d-old primary neuronal cultures made from embryonic chick telencephalon (Lewin et al 1992a). The potassium stimulated ['HIGABA release from these relatively young cultures was not calcium dependent, indicating that no or few synaptic vesicles are developed at day six in vitro (Lewin et al 1992a). The present study was made with a more mature culture.…”

mentioning

confidence: 99%

Inhibition of SKF 89976–A of the y–aminobutyric acid release from primary neuronal chick cultures

Lewin

Mattsson

Grahn

et al. 1994

Acta Physiologica Scandinavica

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Neuronal cultures were made from the 8-d-old embryonic chick telencephalon. The primary culture model was further improved, the medium composition was modified, and the cells grown for 10 d, which allowed the development of relatively differentiated neurones. A superfusion protocol was developed and applied to study the release of [3H]-gamma-aminobutyric acid ([3H]GABA). High endogenous activity levels of glutamate decarboxylase (GAD) and of a Ca-dependent potassium stimulated [3H]GABA release were used as criteria for GABAergic differentiation. The influence of the non-substrate inhibitor of GABA transport, SKF 89976-A, on the GABA release, was studied using the primary neuronal culture. The release was found to be inhibited by SKF 89976-A at higher concentrations (= 400 microM).

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On the activity of ?-aminobutyric acid and glutamate transporters in chick embryonic neurons and rat synaptosomes

Cited by 9 publications

References 19 publications

Regulation of γ-Aminobutyric Acid (GABA) Transporters by Extracellular GABA

Regulation of γ-Aminobutyric Acid (GABA) Transporters by Extracellular GABA

Glutamate transport in cultures from developing avian cerebellum: Presence of GLT-1 immunoreactivity in Purkinje neurons

Inhibition of SKF 89976–A of the y–aminobutyric acid release from primary neuronal chick cultures

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