Vesicle Pool Heterogeneity at Hippocampal Glutamate and GABA Synapses

Glutamate and GABA are the major fast excitatory and inhibitory neurotransmitters, respectively, in the CNS. Although glutamate and GABA have clearly distinct postsynaptic actions, we are just beginning to appreciate that presynaptic differences between glutamatergic and GABAergic neurons may contri...

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Bibliographic Details
Published in:The Journal of neuroscience 2007-09, Vol.27 (37), p.9846-9854
Main Authors: Moulder, Krista L, Jiang, Xiaoping, Taylor, Amanda A, Shin, Wonchul, Gillis, Kevin D, Mennerick, Steven
Format: Article
Language:English
Subjects:
Animals
Cells, Cultured
Endocytosis - physiology
Exocytosis - physiology
gamma-Aminobutyric Acid - metabolism
Glutamic Acid - metabolism
Hippocampus - metabolism
Rats
Synapses - metabolism
Synaptic Vesicles - metabolism
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Summary:Glutamate and GABA are the major fast excitatory and inhibitory neurotransmitters, respectively, in the CNS. Although glutamate and GABA have clearly distinct postsynaptic actions, we are just beginning to appreciate that presynaptic differences between glutamatergic and GABAergic neurons may contribute to distinct functions of these transmitter systems. We therefore probed possible differences between the functional synaptic vesicle populations of glutamatergic and GABAergic neurons. We examined superecliptic synaptopHluorin (SpH) fluorescence during 20 Hz electrical stimulation in transfected hippocampal neurons and identified the phenotype of SpH-fluorescent synapses with post hoc immunostaining. With 200 stimuli (10 s), individual glutamate synapses displayed considerably more variability in peak SpH fluorescence than GABA synapses, without a strong difference in the mean SpH fluorescence increase. This spatial heterogeneity could not be accounted for by differences in endocytosis, which was nearly constant over these short time periods across glutamate and GABA synapses. Instead, variability in vesicle exocytosis correlated with variability in total vesicle staining and in measures of the total recycling pool size. Differences were also evident using FM1-43 [N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] uptake. These data support the idea that the population of glutamate synapses exhibits more heterogeneity in release properties than the population of GABA synapses, possibly correlated with glutamatergic synaptic malleability.
ISSN:0270-6474
1529-2401
DOI:10.1523/JNEUROSCI.2803-07.2007