Magnetic field exposure device for patch-clamp measuring system

A device was developed that enables in situ optical and electrical observations of a single cell under exposure to a magnetic field. Electric current through a flat conductor sheet made a homogeneous magnetic field above the sheet. The sheet was made of brass, 30 mm × 30 mm to 60 mm × 660 mm and 0.3 mm thick, with a hole 2 mm in diameter in the center of the sheet for the light path of a microscope. An electric current of diverse waveforms was supplied by a function generator through an amplifier, generating a magnetic field of the same waveform up to 0.14 mT. The sheet was laid concentrically on the stage of a microscope. The homogeneity of the field over a 40 mm × 40 mm sheet was estimated to be 5% in the vertical and 0.1% in the horizontal directions for a 1 mm shift of a cell. A sheet does not hinder movement of the patch-clamp attachments and leaves space for a pair of coils to compensate the geomagnetic field on the stage of the microscope. The electric noise caused by the field was so small that it could be canceled in the data collection process.