ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract— Synaptosomal release and exchange of [3H]GABA were studied by a superfusion technique which minimizes reuptake. The release of [3H]GABA was increased by depolarizing concentrations of KCl and showed calcium-dependence. Superfusion with 1-1000 μm unlabelled GABA caused a dose dependent, saturable increase in the release of radioactivity by homoexchange. The exchange process showed high substrate specificity: among the various amino acids and putative neurotransmitters tested, only γ-amino-β-hydroxybutyric acid was a good stimulator of [3H]GABA release. Superfusion with sodium-free medium (NaCl replaced by sucrose) virtually abolished homoexchange. Ouabain also increased the release of [3H]GABA, and its action was additive to that of unlabelled GABA.The presence of exchange at concentrations that are in the range of the high affinity uptake system, the apparent similarity between calculated rates of exchange and initial uptake rates, the non-detectability of exchange in a condition (Na+ deprivation) which inhibits high affinity uptake, and the lack of decrease of actual GABA concentration in incubation media used for uptake experiments, all suggest that homoexchange accounts for a substantial part of the synaptosomal accumulation of [3H]GABA generally interpreted as high affinity uptake.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1975.tb03905.x
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