Nonlinearities between inhibition and T-type calcium channel activity bidirectionally regulate thalamic oscillations
- Department of Pharmacology, University of Virginia, United States
- Department of Neurosurgery, Massachusetts General Hospital, United States
- Department of Psychology, Harvard University, United States
- Princeton Neuroscience Institute, Princeton University, United States
- Department of Neurology, Stanford University, United States
Figures
Figure 1
Individual GAT1 or GAT3 blockade strengthens thalamic oscillations, but dual GAT1+GAT3 blockade abolishes oscillations.
(A) Slice recording setup and sample analysis. Acute thalamic slices were bathed in bicuculline to block GABAA receptors. A brief voltage stimulus (0.5 ms, 10 V) was applied with a bipolar electrode …
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Figure 1—source data 1
Oscillation measures in response to different GABA transporter blockade conditions.
Oscillation durations for each slice that was perfused with control, NO-711 (GAT1 blockade), SNAP-5114 (GAT3 blockade) or combined NO-711+ SNAP-5114 (dual blockade) (Figure 1D). Oscillation periods for each slice that was perfused with control, NO-711 or SNAP-5114 (Figure 1E). Oscillation durations for each slice that was perfused with combined NO-711+ SNAP-5114 for 60 min (Figure 1F). Phase 1 is baseline and phase 2 is drug perfusion.
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig1-data1-v2.zip
Figure 2 with 1 supplement
Post-inhibitory, low-threshold rebound spikes and bursts in thalamocortical neurons are bidirectionally modulated by GABAB receptor-mediated conductance waveforms.
(A) Dynamic clamp setup. A thalamocortical neuron was patched in the whole-cell configuration. The applied current was computed from the instantaneous voltage and a command conductance waveform over …
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Figure 2—source data 1
LTS and burst features in response to IPSCs recorded with dynamic clamp (dynIPSCs).
Analyzed LTS and burst features for each recorded IPSC response. Averaged LTS and burst features for each neuron, for dynIPSCs scaled by 200% (Figure 2D, Figure 2—figure supplement 1B). Averaged LTS and burst features for each neuron, for dynIPSCs across all conductance amplitude scales (Figure 2E, Figure 2—figure supplement 1C).
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig2-data1-v2.zip
Figure 2—figure supplement 1
Post-inhibitory, low-threshold rebound spikes and bursts in thalamocortical neurons are bidirectionally modulated by GABAB receptor-mediated conductance waveforms.
(A) Depiction of post-inhibitory rebound LTS measures in (B) and (C). (B) Distributions of post-inhibitory rebound LTS measures over all 47 recorded neurons across dynIPSCs shown in Figure 2B. For …
Figure 3 with 1 supplement
Model thalamocortical neurons reproduce GABAB IPSC and rebound responses.
(A) Model optimization workflow. (B) Sample double-exponential curve fits (red) to averaged current pulse responses (blue) for an example neuron. The dashed lines correspond to the curves …
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Figure 3—source data 1
Parameters and errors for optimized model thalamocortical neurons.
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig3-data1-v2.zip
Figure 3—figure supplement 1
Additional fits of simulated simIPSC responses to recorded dynIPSC responses for selected neurons.
Figure 4 with 1 supplement
Well-fitted model and recorded neurons show similar low-threshold rebound spike probabilities and latencies in response to different GABAB IPSC waveforms.
(A) Distributions of post-inhibitory, low-threshold rebound spike measures over the 31 well-fitted model neurons across GABAB IPSC waveforms shown in Figure 2B (*p<0.05, **p<0.01, ***p<0.001, …
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Figure 4—source data 1
Simulated and recorded LTS and burst features across well-fitted neurons.
Analyzed LTS and burst features for each simulated IPSC response with fast sodium-potassium mechanism (HH2.mod) inserted. Averaged LTS and burst features for each recorded and model neuron, for dynIPSCs scaled by 200% (Figure 4A–B, Figure 4—figure supplement 1A–B). Averaged LTS and burst features for each recorded and model neuron, for dynIPSCs across all conductance amplitude scales (Figure 4C–D, Figure 4—figure supplement 1C–D).
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig4-data1-v2.zip
Figure 4—figure supplement 1
Comparison of other low-threshold rebound spike or rebound burst measures between well-fitted model and recorded neurons.
(A) Distributions of LTS or burst measures over the 31 well-fitted model neurons across GABAB IPSC waveforms shown in Figure 2B (*p<0.05, **p<0.01, ***p<0.001, Friedman’s test). (B) Same as (A) but …
Figure 5 with 1 supplement
T-type calcium channel open probability discrepancy predicts LTS production following GABAB IPSC waveforms.
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Figure 5—source data 1
Open probability discrepancy measures for all simulated traces.
Analyzed open probability discrepancy measures and LTS features for each simulated IPSC response with no fast sodium-potassium mechanism inserted. These are averaged for each model thalamocortical neuron, for traces with and without an LTS (Figure 5C, Figure 5—figure supplement 1).
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig5-data1-v2.zip
Figure 5—figure supplement 1
Detailed analysis of factors contributing to LTS production following GABAB IPSCs.
(A) The LTS response was present across all three compartments, appeared largest in the distal dendrite and correlated with the presence of large intrinsic channel currents. (i) Command sim/dynIPSCs …
Figure 6
Manipulation of the T-type calcium channel inactivation time constant modulates LTS production.
(A) Simulated responses as in Figure 5 with the T channel inactivation time constant halved. The T channel open probability discrepancy failed to reach threshold and no LTS was produced following …
Figure 7 with 1 supplement
Manipulation of GABAB IPSC kinetics bidirectionally modulates low-threshold rebound spike production.
(A) (1) LTS responses to the simGAT3-Block waveform (blue) gradually disappeared as the time constant was increased (with amplitude fixed) to that of the simDual-Block waveform (red). The green …
Figure 7—figure supplement 1
Manipulation of GABAB IPSC kinetics controlled for overall level of inhibition modulates low-threshold rebound spike production.
LTS responses to the simDual-Block waveform (blue) gradually appeared as all parameters of the waveform were shifted (with area under the curve fixed) to that of the simGAT3-Block waveform (yellow), …
Figure 8 with 1 supplement
GABAB-receptor mediated conductance waveforms modulate oscillations produced by two-cell model thalamic networks.
(A) Schematic of a two-cell model network. A reticular thalamic (RT) neuron projected a GABAB receptor-mediated inhibitory synapse (-) to a thalamocortical (TC) neuron, which reciprocally projected …
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Figure 8—source data 1
Oscillation measures for two-cell model thalamic networks using different GABAB receptor activation waveforms (simIPSCs).
Oscillation measures for each network simulation. Averaged oscillation measures for each two-cell network (Figure 8D).
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig8-data1-v2.zip
Figure 8—figure supplement 1
Additional information on two-cell model thalamic networks.
(A) Distributions of oscillation index over all 24, two-cell networks. These values were artificially high because two-cell network oscillations are highly stereotyped. (*p<0.05, ***p<0.001, …
Figure 9
GABAB-receptor-mediated conductance waveforms modulate oscillations produced by 200 cell model thalamic networks.
(A) Schematic of a 200 cell model network. Each reticular thalamic (RT) neuron projected GABAB receptor-mediated inhibitory synapses (-) to nine nearby thalamocortical (TC) neurons. Each TC neuron …
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Figure 9—source data 1
Oscillation measures for 200 cell model thalamic networks using different GABAB receptor activation waveforms (simIPSCs).
List of candidate model thalamocortical neurons. Oscillation measures for each network simulation, for both TC-homogeneous and TC-heterogeneous networks. Averaged oscillation measures for each TC-homogeneous 200 cell network (Figure 9D). Averaged oscillation measures for each TC-heterogeneous 200 cell network (Figure 9E).
- https://cdn.elifesciences.org/articles/59548/elife-59548-fig9-data1-v2.zip
Author response image 1
Individual GAT1 or GAT3 blockade strengthens thalamic oscillations, but dual GAT1+GAT3 blockade abolishes oscillations.
Spectrograms for example evoked epileptiform oscillations at baseline and 40 minutes after perfusing with (i) control (no drug added), (ii) 4 µM NO-711 (GAT1 blocker), (iii) 100 µM SNAP-5114 (GAT3 …
Author response image 2
With GABAA receptors present, GABAB-receptor mediated conductance waveforms still modulate oscillations produced by 2-cell model thalamic networks.
(A) Schematic of a 2-cell model network with GABAA receptors present (cf. Figure 8A). (B) Example 2-cell network responses under different GABAB receptor conditions. The same TC model neuron and …
Author response image 3
GABAB-receptor mediated conductance waveforms modulate oscillations produced by 200-cell model thalamic networks with GABAA receptors present.
(A) Schematic of a 200-cell model network with GABAA receptors present (cf. Figure 9A). (B) Sample spike raster plots of the same TC-heterogeneous network and the same simulation conditions as that …
Author response image 4
Burst latencies were more variable following simIPSCs corresponding to single GAT blockade across well-fitted model neurons.
(A) Distributions of burst latency jitter (standard deviation of burst latencies across all trials) over the 31 well-fitted model neurons across GABAB IPSC waveforms shown in Figure 2B (* p < 0.05, …
Videos
Video 1
Voltage and T-type calcium channel open probability discrepancy trajectories in response to simGAT3-Block and simDual-Block GABAB IPSCs.
Video 2
Voltage and T-type calcium channel open probability discrepancy trajectories in response to all pharmacological GABAB IPSCs.
Video 3
Voltage and T-type calcium channel open probability discrepancy trajectories in response to GABAB IPSCs with two different time constants.
Simulated traces for the example neuron of Figure 3, resampled at 1 ms intervals, in response to GABAB IPSCs using the simDual-Block waveform, but with time constants set to 2.0 (yellow) or 2.3 …
Video 4
Voltage and T-type calcium channel open probability discrepancy trajectories in response to GABAB IPSCs with varying time constants.
Same as Video 3 but in response to all GABAB IPSC time constants shown in Figure 7A2. (A-F) See descriptions for Video 1. There appears to be a threshold for the slope of the open probability …
Tables
Table 1
Average change of LTS and burst features relative to dynControl responses.
For LTS and burst probability, Friedman’s test with multiple comparison was used across all four groups. Due to the lack of LTS response to dynDual-Block, the comparison between dynControl and dynDua…
| dynGAT1-Block | dynGAT3-Block | dynDual-Block | |
|---|---|---|---|
| Burst Probability | +63%, p=0.0018 | +106%, p=1.7×10−7 | −82%, p=0.030 |
| Burst Latency | +4.6%, p=0.034 | +58%, p=1.1×10−9 | no change, p=0.066 |
| LTS Probability | +26%, p=0.0080 | +39%, p=0.0015 | −88%, p=4.8×10−6 |
| LTS Latency | no change, p=0.97 | +53%, p=3.7×10−9 | +254%, p=0.044 |
| Spikes Per LTS | +62%, p=1.3×10−6 | +93%, p=9.3×10−7 | no change, p=0.095 |
| LTS Peak Value (mV) | +2.5 ± 0.5 mV, p=1.4×10−4 | +3.3 ± 0.8 mV, p=5.2×10−4 | no change, p=0.33 |
| LTS Maximum Slope | +52%, p=2.6×10−9 | +82%, p=1.4×10−9 | no change, p=0.068 |
Table 2
Parameter values of GABAB-mediated inhibitory conductance waveforms used in dynamic clamp experiments.
These values (with the amplitudes scaled by 200%) correspond to the conductance templates shown in Figure 2B. , amplitude coefficient; , rise time constant; , fast decay time constant; , …
| dynControl | 16.00 | 52.00 | 90.10 | 1073.20 | 0.952 |
| dynGAT1-Block | 24.00 | 52.00 | 90.10 | 1073.20 | 0.952 |
| dynGAT3-Block | 8.88 | 38.63 | 273.40 | 1022.00 | 0.775 |
| dynDual-Block | 6.32 | 39.88 | 65.80 | 2600.00 | 0.629 |
