Presynaptic GABAB receptors functionally uncouple somatostatin interneurons from the active hippocampal network
- Institute for Integrative Neuroanatomy, Charité - Universitätsmedizin Berlin, Germany
- Centre for Discovery Brain Sciences, University of Edinburgh, United Kingdom
- Institute for Physiology II, Faculty of Medicine, University of Freiburg, Germany
- Institute for Physiology I, Faculty of Medicine, University of Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Germany
Figures
Figure 1 with 1 supplement
Synaptic inputs onto SOM-INs are strongly inhibited by presynaptic GABABR activation.
(A) A reconstruction of a SOM-IN showing soma and dendrites (black) and axon (red) with respect to the layers of the CA1 area. Inset (top left), intrinsic physiological response to current …
Figure 1—figure supplement 1
GABABR-mediated inhibition of EPSCs in SOM-INs in the mouse hippocampus.
(A) Representative EPSCs evoked in the presence of 10 µM bicuculline under control conditions, and following sequential baclofen (2 µM) and CGP (5 µM) bath application. (B) Summary bar chart of EPSC …
Figure 2
Unitary EPSCs from PCs onto SOM-INs are strongly inhibited by presynaptic GABABRs.
(A) Reconstruction of a synaptically coupled CA1 PC (soma/dendrites in blue, axon in green) and SOM-IN pair (soma/dendrites in black, axon in red). Inset (bottom right) shows a train of APs (upper …
Figure 3 with 3 supplements
Localization of the GABAB1 subunit to axon terminals contacting SOM-IN dendrites in str. oriens.
(A) Electron micrograph showing the localization of GABAB1 (6 nm particles) to synaptic membranes, identified by immunoreactivity for CaV2.1 (12 nm), and extrasynaptic membrane of axon terminals of …
Figure 3—figure supplement 1
Subcellular distribution of the GABAB1 subunit in boutons contacting dendritic shafts of oriens-alveus INs in the rat hippocampus as revealed by the SDS-FRL method.
(A) Low-power electron micrograph showing an mGluR1α-immunoreactive dendritic shaft (15 nm immunogold particles on the protoplasmic face/P-face/of the plasma membrane) of a putative SOM-expressing …
Figure 3—figure supplement 2
Colocalization of genetically encoded ChR2-YFP with mGluR1α on putative SOM-IN dendrites.
(A) A representative overview image of str. oriens in a SOM-ChR2-YFP mouse, which is densely labelled for YFP (18 nm immunogold). A region of interest on the P-face is indicated by solid lines. (B) …
Figure 3—figure supplement 3
High GABAB1 subunit surface density on YFP-positive dendritic shafts located in str. oriens from SOM-ChR2-YFP mice as revealed by the SDS-FRL method.
(A) Electron micrograph showing a SOM-ChR2-YFP-immunoreactive dendritic shaft (DenSOM), which is immunolabelled for YFP (18 nm immunogold particles) and GABAB1 (6 nm). (B) Summary bar chart …
Figure 4
GABAB1 expression on inhibitory and excitatory axon terminals forming synapses onto SOM-IN dendrites.
(A) Electron micrographs showing immunogold labeling for GABAB1 (6 nm, arrows) on VGAT-immunonegative (bVGAT-) and VGAT-immunopositive (bVGAT+;12 nm) axon terminals contacting a …
Figure 5 with 1 supplement
SOM-IN output synapses are inhibited by GABABRs.
(A) Confocal image stack of a recorded and biocytin-filled CA1 PC (white pseudocolor) in a slice from SOM-Cre transgenic mouse transfected with ChR2-tdTomato (tom, red). The slice was counterstained …
Figure 5—figure supplement 1
Whole-cell baclofen-mediated currents in optogenetic experiments from CA1 PCs of the mouse hippocampus.
(A) Summary bar chart of holding currents in voltage-clamped CA1 PCs (held at −65 mV) recorded for optogenetic stimulation experiments in control conditions, in 10 µM baclofen and in 5 µM CGP. (B) …
Figure 6
GABAB1 subunit expression and localization on SOM-IN axon terminals.
(A–C) Electron micrographs showing GABAB1 (6 nm particles, red overlay) localized to the active zone (az) (A), identified by immunolabeling for Cav2.1 (12 nm, green overlay), to the perisynaptic …
Figure 7 with 2 supplements
Presynaptic GABABR-mediated inhibition functionally uncouples SOM-INs from the local network.
(A) Dual extracellular field (upper) and whole-cell (lower) recordings from a CA1 SOM-IN in longitudinal acute hippocampal slice during theta frequency oscillations induced by bath application of 50 …
Figure 7—figure supplement 1
SOM-IN spiking is abolished by GABABR activation in the mouse hippocampus.
(A) Representative traces during 2 mM kainate puff application to the str. radiatum, showing the extracellular field oscillations (upper traces) and the discharge of a whole-cell recorded SOM-IN …
Figure 7—figure supplement 2
Abolished SOM-IN spiking is due to GABABRs activation in CA1 str. oriens of the mouse hippocampus.
(A) Representative trace during 2 mM kainate puff application to the str. radiatum, showing the extracellular field oscillations (upper traces) and the discharge of a whole-cell recorded SOM-IN …
Author response image 1
Summary bar charts of the surface densities of immunogold particles for GABAB1 subunit in excitatory and inhibitory axon terminals forming synapses onto SOM-IN dendrites in the mouse (left) and the rat hippocampus (right) detected using the B17 and A25 primary antibodies, respectively (see Materials and methods for further detail).
Superimposed open circles represent density values from individual boutons.
Author response image 2
Dependence of baclofen mediated presynaptic inhibition and paired-pulse ratio on the EPSC and IPSC ampli-tudes.
(A) Baclofen-induced presynaptic inhibition of EPSCs (filled circles) and IPSCs (open circles) plotted as a function of PSC amplitude. Based on a linear regression analysis, neither EPSCs (F(d.f. …
Tables
Key resources table
| Reagent type (species) or resource | Designation | Source or reference | Identifiers | Additional information |
|---|---|---|---|---|
| Genetic reagent (R. norvegicus) | Wild-type rat | Charles River | Crl:WI | Rats used for immunoelectron microscopy |
| Genetic reagent (R. norvegicus) | vGAT-YFP rat | PMID: 17517679 | Rats used for acute slice experiments | |
| Genetic reagent (M. musculus) | Wild-type mouse | Charles River | C57/Bl6J CRL | Mice used for acute slice experiments |
| Genetic reagent (M. musculus) | Som-Cre mouse | Jackson Laboratory; 013044 | Ssttm2.1(cre)Zjh/J | |
| Genetic reagent (M. musculus) | Ai32 mouse | Jackson Laboratory; 024109 | RCL-ChR2(H134R)/EYFP | |
| Antibody | Anti-GFP | Aves labs, USA | Aves labs:GFP-1010 | chicken polyclonal (1:25000) |
| Antibody | Anti- Cav2.1 | Frontier Institute, JAPAN | Frontier Institute:VDCCa1A-GP-Af810; RRID:AB_2571851 | guinea pig polyclonal (1:50) |
| Antibody | Anti- VGAT | Frontier Institute, JAPAN | Frontier Institute. VGAT-GP-Af1000; RRID:AB_2571624 | guinea pig polyclonal (1:44) |
| Antibody | Anti-VGLUT1 | Frontier Institute, JAPAN | Frontier Institute: VGluT1-Go-Af310; RRID:AB_2571617 | goat polyclonal (1:400) |
| Antibody | Anti-mGluR1α | Frontier Institute, JAPAN | Frontier Institute: mGluR1a-GP-Af660; RRID:AB_2571801 | guinea pig polyclonal (1:500) |
| Antibody | Anti-Somatostatin | Peninsula Laboratories, USA | Peninsula Laboratories:T-4103.0050 | rabbit polyclonal (1:2000) |
| Antibody | Anti-GABAB1(B17) | PMID: 11849296 | Rabbit polyclonal; against aa 901–960; (1:50) | |
| Antibody | Anti-GABAB1(A25) | PMID: 16427742 | Rabbit polyclonal; against aa 857–960; (1:200) | |
| Antibody | 6 nm anti-Rabbit IgG (secondary) | Jackson ImmunoResearch Europe, UK | Jackson ImmunoResearch E:711-195-152 | (1:30) |
| Antibody | 12 nm anti-Guinea pig (secondary) | Jackson ImmunoResearch Europe, UK | Jackson ImmunoResearch E:706-205-148 | (1:30) |
| Antibody | 12 nm anti-Goat (secondary) | Jackson ImmunoResearch Europe, UK | Jackson ImmunoResearch E:705-205-147 | (1:30) |
| Antibody | 18 nm anti-Chicken (secondary) | Jackson ImmunoResearch Europe, UK | Jackson ImmunoResearch E:703-215-155 | (1:30) |
| Antibody | 3 nm anti-Guinea pig (secondary) | Nanopartz, USA | Nanopartz:CA11-3-FCDAGG-DIH-50–1 | (1:800) |
| Antibody | Alexa Fluor 405,488,546 Anti-Rabbit (secondaries) | Invitrogen, UK | (1:500) | |
| Other | Alexa Fluor 647 Streptavidin | Invitrogen, UK | Invitrogen:S21374 | (1:500) |
| Chemical compound, drug | NBQX | Abcam Biochemicals, UK | ab120046 | |
| Chemical compound, drug | DL-AP5 | Abcam Biochemicals, UK | ab120271 | |
| Chemical compound, drug | Bicuculline | Abcam Biochemicals, UK | ab120108 | |
| Chemical compound, drug | Gabazine | Abcam Biochemicals, UK | ab120042 | |
| Chemical compound, drug | R-Baclofen | Abcam Biochemicals, UK | ab120325 | |
| Chemical compound, drug | CGP-55845 | Abcam Biochemicals, UK | ab120337 | |
| Chemical compound, drug | SCH23,390 | Tocris, UK | 0925/10 | |
| Chemical compound, drug | Kainate | Tocris, UK | 0222/1 | |
| Chemical compound, drug | Carbcahol | Abcam Biochemicals, UK | ab141354 | |
| Software, algorithm | GraphPad Prism | GraphPad Software, USA | ||
| Software, algorithm | WinWCP | University of Strathclyde, UK | http://spider.science.strath.ac.uk/sipbs/software_ses.htm | |
| Software, algorithm | pClamp | Axon Instruments, USA | ||
| Software, algorithm | MATLAB | Mathworks, USA | ||
| Software, algorithm | StimFit | PMID: 24600389 | ||
| Software, algorithm | Fiji | http://fiji.sc |
