Investigation of one compound effect on main neuronal properties in a native network final

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Investigation of one compound
potential effects on main
neuronal properties in a native
neuronal network
December, 2011

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SUMMARY
Introduction
Aim of the study
Materials & Methods
Preparation of acute rat hippocampal slices
Slice perfusion and temperature control
Stimulation protocols
Experiments
Evaluation of Compound A on I/O properties
Evaluation of Compound A on Paired-Pulse Facilitation
Evaluation of Compound A on basal synaptic transmission
Evaluation of Compound A on Long-Term Potentiation
Evaluation of Compound A on Long-Term Depression
Evaluation of Compound A on Paired-Pulse Inhibition

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INTRODUCTION
The aim of the study is to evaluate one compound effect on the main neuronal properties in
a native neuronal network, such as the hippocampal slice.
For this aim, the effect of the compound will be investigated in several protocols:
Input/Output (I/O) curve (overall effect on excitability)
Paired-Pulse Facilitation (PPF; effect on short-term synaptic plasticity)
Basal synaptic transmission (balance between excitatory and inhibitory transmission)
Long-Term Potention (LTP) and Long-Term Depression (LTD) (long term synaptic
plasticity mechanisms)
Extracellular recordings (EPSP) are performed with Multi-Electrode Arrays (MEA).

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MATERIALS & METHODS
Preparation of acute rat hippocampal slices
Experiments are carried out with Sprague Dawley rats between 3 and 4 weeks of age provided by
Elevage Janvier.
Hippocampal slices (400 µm thickness) are cut with a MacIIwain tissue chopper in a ice-cold oxygenated
sucrose solution (Saccharose 250, Glucose 11, NaHCO3 26, KCl 2, NaH2PO4 1.2, MgCl2 7 and CaCl2 0.5 in
mM).
Then, slices are incubated at room temperature for at least 1h in ACSF of the following composition:
Glucose 11, NaHCO3 25, NaCl 126, KCl 3.5, NaH2PO4 1.2, MgCl2 1.3, CaCl2 2 in mM.
Slice perfusion and temperature control
During experiments, the slices are continuously perfused with the ACSF (bubbled with 95% O2–5% CO2)
at the rate of 3 mL/min with a peristaltic pump (MEA chamber volume: ~1 mL). Complete solution
exchange in the MEA chamber is achieved 20 s after the switch of solutions.
The perfusion liquid is continuously pre-heated at 37°C just before reaching the MEA chamber with a
heated-perfusion cannula (PH01, MultiChannel Systems, Reutlingen, Germany). The temperature of the
MEA chamber is maintained at 37 ± 0.1°C with a heating element located in the MEA amplifier
headstage.

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MATERIALS & METHODS
Stimulation protocols
• Input/Output (I/O) curve: stimulation intensities between 100 and 800 μA, by 100 μA steps.
• Paired-Pulse Facilitation (PPF): Two pulses with a decreasing inter-stimulus interval (e.g. 300 ms,
200 ms, 100 ms, 50 ms, 25 ms) are applied at Schaeffer collaterals. Both stimuli are of equal
intensity and settled at 40 % of the maximal amplitude responses.
• Basal synaptic transmission: The stimulus intensity is set to 40% Imax at 0.033Hz.
• Long-Term Potentiation (LTP): two 1 s trains of stimulations at 100 Hz, applied at 20 s intervals.
• Long-Term Depression (LTD): 900 stimulations at 1 Hz.
• Paired-Pulse Inhibition (PPI): Two pulses with a 20 ms inter-pulse interval are applied every minute
with an intensity evoking PPI of the second PS

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EXPERIMENTS
Evaluation of Compound A on I/O properties
No difference is observed between
the I/O curve determine in control
conditions and in the presence of
compound A.
I/O c u rv e
0 2 0 0 4 0 0 6 0 0 8 0 0
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
C o n tro l
C o m p o u n d A
S tim u lu s In te n sity (µ A )
fEPSPamplitude(µV)

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EXPERIMENTS
Evaluation of Compound A on PPF characteristics
No significant difference is observed
for the PPF profile between control
conditions and in the presence of
compound A.
P a ire d P u lse Fa cilita tio n
0 1 0 0 2 0 0 3 0 0
1 .0
1 .2
1 .4
1 .6
1 .8
2 .0
C o n tro l
C o m p o u n d A
In te r-stim u lu s In te rv a l (m s)
fEPSP2/fEPSP1

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EXPERIMENTS
Evaluation of Compound A on basal synaptic transmission
Compound A slightly decreases the
basal synaptic transmission. At
endpoint, the fEPSP amplitude is
decreased by about 12%.
B a sa l syn a p tic tra n sm issio n
0 1 0 2 0 3 0 4 0
0 .4
0 .6
0 .8
1 .0
1 .2
C o m p o u n d A
T im e (m in )
NormalizedfEPSPamplitude

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EXPERIMENTS
Evaluation of Compound A on LTP
In control conditions, HFS induces a
strong and durable potentiation of
evoked-responses, which stabilized
around 55%.
Compound A decreases the basal
synaptic transmission by about 10%,
as observed previously. However, HFS-
induced potentiation remains very
close to the one in control conditions
(the potentiation is of 56 ± 7% in the
presence of Compound A versus 57 ±
5% in control conditions, at endpoint).
LT P S tim SC
1 0 3 0 5 0 7 0 9 0
1 .0
1 .5
2 .0
2 .5
C o m p o u n d A
T im e (m in )
NormalizedfEPSPamplitude

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EXPERIMENTS
Evaluation of Compound A on LTD
Compound A slightly decreases the
basal synaptic transmission.
However, LFS-induced LTD does not
substantially differ in hippocampal
slices exposed to Compound A and in
control conditions (the depression is
of 57 ± 1% in the presence of
Compound A versus 64 ± 4% in
control conditions, at endpoint.
LT D Stim SC
1 0 3 0 5 0 7 0 9 0
0 .0
0 .4
0 .8
1 .2
C o m p o u n d A
T im e (m in )
NormalizedfEPSPamplitude

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EXPERIMENTS
Evaluation of Compound A on PPI
Compound A does not modify the
paired-pulse inhibition (PS ratio
remains steady over the 30 minute
exposure).
P a ire d P u lse In h ib itio n
0 1 0 2 0 3 0 4 0 5 0
0 .0
0 .5
1 .0
1 .5
2 .0
P e a k 2
N o rm a liz e d R a tio P 2 /P 1
P e a k 1
C o m p o u n d A
T im e (m in )

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Input/Output properties are not modified by Compound A
Paired-pulse facilitation is not modified by Compound A
Compound A slightly decreases the fEPSP amplitude, by about 10%.
The LTP amplitude is not modified in the presence of Compound A, thereby indicating
that this compound does not modify NMDA receptors function and downstream
mechanisms involved in LTP establishment and maintain.
The LTD amplitude is not modified in the presence of Compound A. This further
confirms that Compound A does not modify NMDA receptors function and downstream
pathways involved in the establishment of LTD and its maintain.
The PPI ratio is not modified in the presence of Compound A, thereby indicating that
Compound A does not change the balance between excitatory and GABAA-mediated
inhibitory transmission
CONCLUSION

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