A Procedure For Recording From Oocytes - Warner OC-725C User Manual

A Procedure for Recording from Oocytes

Initial Electrode Placement
1) Make sure that the bath electrodes are submerged in the chamber (or in the
agar bridge wells with the agar bridges completing the circuit to the bath) and
the oocyte is stable on the chamber floor.
2) Install the voltage and current pipettes onto their respective holders but do not
yet place them in the chamber bath solution.
Voltage Electrode Placement
3) Advance the voltage recording electrode into the bath. The VOLTAGE ELECTRODE
METER will indicate (in mV) the potential between the electrode and the bath.
4) If there is no voltage reading and you are sure that the pipette tip is in the bath
solution, perform the following checks:
a) make sure that all cables are connected properly.
b) inspect the voltage electrode to see if there is a bubble in the pipette which
will cause an open circuit.
5) Using the Vm OFFSET control, adjust the VOLTAGE ELECTRODE potential to read
0 mV. If the junction potential of the voltage electrode can not be adjusted to 0
mV, the electrode holder may be at fault.
(See Electrode Holders, page 17.)
6) To test the resistance of the voltage electrode pipette, depress the ELECTRODE
TEST button. This passes a 10 nA current across the voltage electrode. The
VOLTAGE ELECTRODE METER will display the resulting potential in mV. The
resistance of the electrode can be easily calculated by dividing the current into
the potential. The resulting answer will be expressed in Ω. For example, if
the electrode test indicates that a potential of 25.0 mV is produced by the 10 nA
test current, then
NOTES:
a) A simpler calculation is to divide the voltage readout by 10 and append the
units of MΩ. (e.g., 25 mV = 2.5 MΩ)
b) The calculated resistance value may vary widely from pipette to pipette but
should be less than 4 MΩ for the voltage electrode.
www.warneronline.com
27