title: Basal GABA regulates GABA(B)R conformation and release probability at single hippocampal synapses.
abstract: 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.
authors.affiliation: Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Tal
authors.initials: T
authors.lastname: Laviv
authors.forename: Inbal
authors.initials: I
authors.lastname: Riven
authors.forename: Iftach
authors.initials: I
authors.lastname: Dolev
authors.forename: Irena
authors.initials: I
authors.lastname: Vertkin
authors.forename: Bartosz
authors.initials: B
authors.lastname: Balana
authors.forename: Paul A
authors.initials: PA
authors.lastname: Slesinger
authors.forename: Inna
authors.initials: I
authors.lastname: Slutsky
mesh_terms: D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001418:Baclofen / Q000494:pharmacology; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018682:GABA Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D018613:Microscopy, Confocal / Q000379:methods; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009557:Nipecotic Acids / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D011336:Probability; D011487:Protein Conformation / Q000187:drug effects; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000737:chemistry / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000779:Anesthetics, Local; C092350:FM 4-64; C073804:FM1 43; D018682:GABA Agents; D009557:Nipecotic Acids; D009943:Organophosphorus Compounds; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018080:Receptors, GABA-B; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; C107353:CGP 54626; D013779:Tetrodotoxin; D004533:Egtazic Acid; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; C045598:N-(4,4-diphenyl-3-butenyl)nipecotic acid; D001418:Baclofen; D002118:Calcium