1. Maximilian Darrah, John Partridge, Stefano Vicini
Department of Biology, Department of Pharmacology and Physiology
Georgetown University, Washington, D.C.
GABAergic control of excitatory input to striatal spiny
projection neurons (SPNs)

2. Motor Function – Basal Ganglia

3. Striatonigral and Striatopallidal pathways
Gerfen, (2006) Nat Neurosci 9(2):157-8
These outputs facilitates or inhibits movement initiation and control

4. Striatal Innervation
Glutamate
GABA
GABA
-Excitatory inputs from cortex,
thalamus
-Inhibitory inputs from
GABAergic interneurons and
SPNs/MSNs collaterals
-Modulatory inputs (dopamine)
from SNc
Adapted from Tepper et al., 2004 Curr Opin Neurobiol 14:685.
LTS
TH
SPN

5. Postsynaptic GABA current

6. Subunit composition determines pharmacology
and function of the receptor
• pharmacological sensitivity
• channel kinetics
• desensitization rates
• regional and subcellular localization.
Tija et al. 2008 Nature Reviews Neuroscience 9:331
α1-6, β1-3, γ1-3, δ, ε, θ1-3, π, ρ1-3
Neil Harrison: Navigating Neuronal Pathways

7. Methods
Calcium Imaging
•Recordings at room
temperature
•Stimulation with a bipolar
Tungsten electrode
•Drug applied via‘y’tubing
system
Acute slice prep
• Post-natal day 13-21
• Dissect out brain
• Cut 250μm coronal slices
containing the striatum
• Incubated in artificial CSF
Y tubing
Stimulating
Electrode

8. GCaMP3 Protein
• Is a genetically encoded calcium indicator (GECI)
• Consists of Green Fluorescent Protein, Calmodulin, and M13
• Modulates fluorescence based on presence or absence of
calcium.
• Cell specificity: drd2;GCaMP3 and drd1;GCaMP3
Figure A taken from Lindenburg et al
ChemBioChem
(13): 349-351
[Ca2+]i
Spikes
50% F/F0
20 mV
10 s

9. Synaptic Activation of Striatopallidal
SPNs in a drd2;GCaMP3 Mouse
Movie at 15x speed

10. GABAzine 10 µM
3.5 s
100% df/f1
3
4
5
6
2
7
9
350 ms
25 %
df/f
GABAzine WashControl
Gabazine effects in drd2 SPNs

11. 20
60
100
Cell1
Cell2
Cell3
Cell4
Cell5
Cell6
Cell7
Cell8
Cell9
Peak (dF/F0)
Peak
Decay time
Latency 350 ms
T of Peak
Gabazine affects peak fluorescence in drd2
SPNs

12. Gabazine effects are specific for drd2 SPNs
0%
50%
100%
150%
200%
P13-P15
drd1
drd2
P19-21
*
*p< 0.005 to control
%control
*

13. Diazepam effects
0%
50%
100%
150%
P13-P15 P19-P21
drd1
drd2
*
%control

14. Conclusions and Future
Directions
Synaptic excitation of SPNs evokes calcium transients that are variable within and
between cells.
Comparing Gabazine’s effects on SPNs in drd1;GCaMP3 and drd2;GCaMP3 mice, we
revealed GABAergic control of the indirect pathway SPNs is much stronger than that of
the direct pathway.
These data are supported by the inhibitory effect of diazepam in the drd2 but not drd1
SPNs and are relevant for the understanding and treatment of movement disorders.

15. Special Thanks to the Vicini Lab
Stefano Vicini
John Partridge
Carissa Winland
Nour Al-Muhtasib
Supported by the Howard Hughes Medical Institute Scholars Program