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Properties of glutamate uptake in salamander Müller cells

Barbour, Boris James; (1991) Properties of glutamate uptake in salamander Müller cells. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Glutamate is a major transmitter in the central nervous system. In order to understand its physiological and pathological actions it is necessary to investigate the properties of the uptake system which removes glutamate from the extracellular space. An important function of glutamate uptake is to maintain the extracellular glutamate concentration below neurotoxic levels. High affinity, sodium-dependent, electrogenic glutamate uptake was measured using whole-cell patch-clamp recording in acutely isolated retinal glial (Müller) cells of the salamander. The ionic dependence of the glutamate uptake current was investigated. Internal sodium and glutamate both inhibited the uptake current. It was activated by intracellular potassium and inhibited by extracellular potassium: therefore glutamate uptake involves counter transport of potassium ions. Replacement of intracellular or extracellular chloride had no effect on the uptake current. The uptake current was maximal near pH 7.3. Second messenger systems were manipulated in order to identify mechanisms regulating the uptake carrier. Variation of the intracellular calcium concentration or inclusion of cGMP, cAMP or GTP-γ-S in the patch pipette had little or no effect on the uptake current. Arachidonic acid induced a progressive and prolonged inhibition of the uptake current. A fluorescence assay was used to measure glutamate uptake, independently of the uptake current. Manoeuvres which changed the uptake current had similar effects on uptake as measured by the fluorescence method. This confirmed that glutamate uptake into Muller cells occurs predominantly by the high affinity, sodium-dependent system and that the uptake current reflects accurately the rate of glutamate uptake into the cell.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Properties of glutamate uptake in salamander Müller cells
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Mueller cells
URI: https://discovery.ucl.ac.uk/id/eprint/10121052
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