Basal GABA Regulates GABABR Conformation and Release Probability at Single Hippocampal Synapses

Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Neuron (Impact Factor: 15.05). 07/2010; 67(2):253-67. DOI: 10.1016/j.neuron.2010.06.022
Source: PubMed


Presynaptic GABA(B) receptor (GABA(B)R) heterodimers are composed of GB(1a)/GB(2) subunits and critically influence synaptic and cognitive functions. Here, we explored local GABA(B)R activation by integrating optical tools for monitoring receptor conformation and synaptic vesicle release at individual presynaptic boutons of hippocampal neurons. Utilizing fluorescence resonance energy transfer (FRET) spectroscopy, we detected a wide range of FRET values for CFP/YFP-tagged GB(1a)/GB(2) receptors that negatively correlated with release probabilities at single synapses. High FRET of GABA(B)Rs associated with low release probability. Notably, pharmacological manipulations that either reduced or increased basal receptor activation decreased intersynapse variability of GB(1a)/GB(2) receptor conformation. Despite variability along axons, presynaptic GABA(B)R tone was dendrite specific, having a greater impact on synapses at highly innervated proximal branches. Prolonged neuronal inactivity reduced basal receptor activation, leading to homeostatic augmentation of release probability. Our findings suggest that local variations in basal GABA concentration are a major determinant of GB(1a)/GB(2) conformational variability, which contributes to heterogeneity of neurotransmitter release at hippocampal synapses.

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Available from: Inna Slutsky, May 22, 2014
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    • "For FRET imaging and analysis, images were 512 3 512 pixels, with a pixel width of 92–110 nm. Intensity-based FRET imaging and analysis was carried as described before (Laviv et al., 2010). "
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    • "In order to exclude potential contribution of donor/acceptor ratio to FRET efficiency measurements, all FRET experiments were performed under saturation conditions of acceptor over donor. Detection of Cer and Cit signals was done using custom-written scripts in MATLAB as described earlier (Laviv et al., 2010). "

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