A high voltage electrometer for recording and iontophoresis with fine-tipped, high resistance microelectrodes

A high voltage electrometer is described which incorporates a controlled current source, direct current monitoring, balance bridge, electrode resistance, and capacitance compensation test circuits. This device is suitable for making biophysical measurements and iontophoresing dyes or enzymes through extremely fine micropipettes with impedances an order of magnitude higher than conventional micropipettes. Such electrodes are useful for recording from the small neurons of the central nervous system in vivo.