title: A constant current source for extracellular microiontophoresis.
abstract: A sophisticated constant-current source suitable for extracellular microiontophoresis of tract-tracing substances, such as Phaseolus vulgaris leucoagglutinin, Biocytin or Fluoro-Gold, is described. This design uses a flyback switched-mode power supply to generate controllable high-voltage and operational amplifier circuitry to regulate current and provide instrumentation. Design features include a fast rise time, +/- 2000 V supply (stable output in < 250 ms), simultaneous load current and voltage monitoring, and separate pumping and holding current settings. Three features of this constant-current source make it especially useful for extracellular microiontophoresis. First, the output voltage monitor permits one to follow changes in the microelectrode resistance during current injection. Second, the voltage-limit (or out-of-compliance) indicator circuitry will sound an alarm when the iontophoretic pump is unable to generate the desired current, such as when the micropipette is blocked. Third, the high-compliance voltage power supply insures up to +/- 20 microA of current through 100 M omega resistance. This device has proven itself to be a reliable constant-current source for extracellular microiontophoresis in the laboratory.
authors.affiliation: Department of Computer and Electrical Engineering, Kansas State University, Manhattan 66506-5602, USA.
authors.forename: T
authors.initials: T
authors.lastname: Walker
authors.forename: N
authors.initials: N
authors.lastname: Dillman
authors.forename: M L
authors.initials: ML
authors.lastname: Weiss
mesh_terms: D001921:Brain / Q000502:physiology; D004553:Electric Conductivity; D004594:Electrophysiology / Q000295:instrumentation; D005456:Fluorescent Dyes; D007478:Iontophoresis / Q000295:instrumentation* / Q000379:methods; D008832:Microchemistry; D013266:Stilbamidines; D013997:Time Factors
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D013266:Stilbamidines