title: New effects of GABAB receptor allosteric modulator rac-BHFF on ambient GABA, uptake/release, Em and synaptic vesicle acidification in nerve terminals.
abstract: Positive allosteric modulators of GABAB receptors have great therapeutic potential for medications of anxiety, depression, etc. The effects of recently discovered modulator rac-BHFF on the key characteristics of GABAergic neurotransmission were investigated in cortical and hippocampal presynaptic nerve terminals of rats (synaptosomes). The ambient level of [(3)H]GABA that is a balance between release and uptake of the neurotransmitter increased significantly in the presence of rac-BHFF (at concentrations 10-30μM). The initial velocity of synaptosomal [(3)H]GABA uptake was suppressed by the modulator. In the presence of GABA transporter blocker NO-711, it was shown that rac-BHFF increased tonic release of [(3)H]GABA from synaptosomes (at concentrations 3-30μM). Rac-BHFF within the concentration range of 0.3-30μM did not enhance inhibiting effect of (±)-baclofen on depolarization-induced exocytotic release of [(3)H]GABA. Rac-BHFF (0.3-30μM) caused dose-dependent depolarization of the plasma membrane and dissipation of the proton gradient of synaptic vesicles in synaptosomes that was shown in the absence/presence of GABAB receptor antagonist saclofen using fluorescent dyes rhodamine 6G and acridine orange, respectively, and so, the above effects of rac-BHFF were not associated with the modulation of presynaptic GABAB receptors. Therefore, drug development strategy of positive allosteric modulation of GABAB receptors is to eliminate the above side effects of rac-BHFF in presynapse, and vice versa, these new properties of rac-BHFF may be exploited appropriately.
authors.affiliation: The Department of Neurochemistry, Palladin Institute of Biochemistry, NAS of Ukraine, 9 Leontovicha Street, Kiev 01601, Ukraine.
authors.forename: N
authors.initials: N
authors.lastname: Pozdnyakova
authors.affiliation: The Department of Neurochemistry, Palladin Institute of Biochemistry, NAS of Ukraine, 9 Leontovicha Street, Kiev 01601, Ukraine.
authors.forename: M
authors.initials: M
authors.lastname: Dudarenko
authors.affiliation: The Department of Neurochemistry, Palladin Institute of Biochemistry, NAS of Ukraine, 9 Leontovicha Street, Kiev 01601, Ukraine. Electronic address: tborisov@biochem.kiev.ua.
authors.forename: T
authors.initials: T
authors.lastname: Borisova
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology; D001572:Benzofurans / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D018682:GABA Agents / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D011522:Protons; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects* / Q000502:physiology*; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C532129:(R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one; D001572:Benzofurans; D018682:GABA Agents; D011522:Protons; D018080:Receptors, GABA-B; D014316:Tritium; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; C080629:saclofen
keywords: GABA release; GABA uptake; GABA(B) receptor allosteric modulator rac-BHFF; ambient GABA; membrane potential; rat brain nerve terminals