Multi-Electrode Array Technique - Characterization of LTP profiles in wt and ko mice

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Characterization of LTP profiles in

WT & KO mice

May, 2009


SUMMARY

  Introduc*on   Aim of the study

  Materials & Methods   Prepara*on of mice hippocampal slices and solu*ons   Perfusion and temperature control   Electrophysiological recordings

  Experiments   Comparison of Long-‐Term Poten*a*on (LTP) profiles from KO and WT mice


INTRODUCTION   The aim of the present study is to compare the profile of Long-‐Term Potenta*on (LTP) recorded in hippocampal slices of Knock-‐Out (KO) mice with the profile of LTP recorded in slices from Wild-‐Type (WT) mice.

  Synap*c transmission and plas*city are recorded in the CA1 region of adult mice hippocampi by s*mula*ng Schaeffer collateral fibres at the CA3/CA1 interface.

  Extracellular recordings (EPSP) are performed with Mul*-‐Electrode Arrays (MEA).


MATERIALS & METHODS

  Prepara*on of acute mice hippocampal slices   Experiments are carried out with KO and WT mice provided by the customer.   Hippocampal slices (350 µm thickness) are cut with a MacIIwain *ssue chopper in a ice-‐cold oxygenated sucrose solu*on

(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 1 h in Ar*ficial Cerebro-‐Spinal Fluid (ACSF) of the following composi*on :

NaCl 126, KCl 3.5, NaH2PO4 1.2, MgCl2 1.3, CaCl2 2, NaHCO3 25, D-‐glucose 11 in mM.

  Perfusion and temperature control   During experiments, the slices are con*nuously perfused with the ACSF (bubbled with 95% O2–5% CO2) at the rate of 3 mL/min with

a peristal*c pump (MEA chamber volume: ~1 mL). Complete solu*on exchange in the MEA chamber is achieved 20 s aber solu*ons exchange.

  The perfusion liquid is con*nuously pre-‐heated at 37°C just before reaching the MEA chamber with a heated-‐perfusion cannula (PH01, Mul*Channel Systems, Reutlingen, Germany).

  The temperature of the MEA chamber is maintained at 37 ± 0.1°C with a Pel*er element located in the MEA amplifier headstage.

  Electrophysiological recordings   Basal synap*c transmission: The s*mulus intensity is set to 40% Imax (determined by an input/output curve) at 0.033Hz.   Long-‐Term Poten*a*on (LTP) protocol: High frequency s*mula*on is induced by two 1s trains at 100 Hz.


EXPERIMENTS Comparison of LTP profiles from KO and WT mice in the CA1 region of hippocampal slices

  Long-‐Term Poten*a*on is strongly impaired in slices from KO mice compared to WT mice.

  Thus, at the end of the experiments, poten*a*on values are 65 ± 8 % in slices from WT mice versus 36 ± 5 % in slices from KO mice.

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  Although a similar LTP profile, a clear difference of LTP amplitude is observed between slices from WT and KO mice. Poten*a*on values are about 30% lower in slices from KO mice than in slices from WT mice throughout the post-‐ HFS period.

CONCLUSION

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Multi-Electrode Array Technique - Characterization of LTP profiles in wt and ko mice