The low impedance of the probe ( typically 7-10 k ohm ) is very important to record neural signals with high S/N ratio and to stimulate neurons effectively. For this reason the MED probe was designed for disposable use. Experience (see below), however, indicates that the probe may be reused if cleaned carefully.

EDTA-Collagenase probe reuse cleaning method

CAUTION: DO NOT TOUCH the surface of the MED probeT, as you may damage the microelectrodes and insulation layer.

1. Pour 0.5 mM EDTA into the MED probe chamber (with slice) and incubate for 30 min.

2. Rinse the chamber with PBS 3 times.

3. Dissolve collagenase type I (Sigma) in PBS at 20 U/ml.

4. Pour collagenase solution into the chamber and incubate for 30 min at 37 C.

5. Discard collagenase solution and rinse with distilled water at least 3 times.

6. Dry the MED probe in a clean bench.

Probe reuse test results

Slices were prepared from 5 week old male C57/BL6 mice hippocampal region. The MED probe was coated according to PEI protocol. Five sweeps of EPSP recording (stimulation 10 to 20 mA) and 30 seconds of spontaneous recording were made for each daily experiment. The probe was cleaned according to EDTA-Collagenase method, and the impedance measured after the experiment. The probe was then coated according to the PEI protocol for the next experiment.