title: Spatial distributions of GABA receptors and local inhibition of Ca2+ transients studied with GABA uncaging in the dendrites of CA1 pyramidal neurons.
abstract: GABA (γ-amino-butylic acid)-mediated inhibition in the dendrites of CA1 pyramidal neurons was characterized by two-photon uncaging of a caged-GABA compound, BCMACM-GABA, and one-photon uncaging of RuBi-GABA in rat hippocampal slice preparations. Although we found that GABA(A)-mediated currents were diffusely distributed along the dendrites, currents elicited at the branch points of the apical dendritic trunk were approximately two times larger than those elsewhere in the dendrite. We examined the inhibitory action of the GABA-induced currents on Ca(2+) transients evoked with a single back-propagating action potential (bAP) in oblique dendrites. We found that GABA uncaging selectively inhibited the Ca(2+) transients in the region adjacent (<20 µm) to the uncaging site, and that GABA uncaging was effective only within a short period after bAP (<20 ms). The strength of inhibition was linearly related to the amplitudes of the GABA currents, suggesting that the currents inhibited a sustained, subthreshold after-depolarization without preventing propagation of bAP. GABA uncaging at the dendritic branch points inhibited Ca(2+) transients farther into dendritic branches (>20 µm). Our data indicate that GABA inhibition results in spatially confined inhibition of Ca(2+) transients shortly after bAP, and suggest that this effect is particularly potent at the dendritic branch points where GABA receptors cluster.
authors.affiliation: Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Kanemoto
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsuzaki
authors.forename: Susumu
authors.initials: S
authors.lastname: Morita
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hayama
authors.forename: Jun
authors.initials: J
authors.lastname: Noguchi
authors.forename: Naoko
authors.initials: N
authors.lastname: Senda
authors.forename: Atsuya
authors.initials: A
authors.lastname: Momotake
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Arai
authors.forename: Haruo
authors.initials: H
authors.lastname: Kasai
mesh_terms: D000200:Action Potentials; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism*; D004058:Diffusion; D004553:Electric Conductivity; D053444:Inhibitory Postsynaptic Potentials; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D002118:Calcium