The Microiontophoretic Approach

Part of the NATO Advanced Study Institutes Series book series (NSSA, volume 1)


The term “microiontophoresis” refers to the passage of an electric current through an ionised solution within a glass micro-pipette resulting in the ejection of a substance from the tip of the micropipette. Comprehensive reviews of this method of drug application have been written by Curtis (1965), Salmoiraghi and Weight (1967) and Krnjevic’ (1964; 1971). For solutions of high conductivity, the amount of ionised substance ejected (Q) is a simple function of the total ionic current flowing through the solution:
$$Q = \frac{{It{\tau _n}}}{{zF}}$$
where Q is the number of ion equivalents, I is current in amperes (A), t is time in seconds, z is the valence, F is Faraday’s constant and τn is the transport number. The transport number of a particular ion through the orifice is dependent on the concentration of ions within and just outside the tip of the micropipette. An ideal transport number is 1.0, but experimentally, values ranging from 0.01 to 0.6 have been obtained for pharmacologically active ions released in vitro (see Table 1, Krnjevic 1971).


Cortical Neurone Retinal Ganglion Cell Drug Application Transport Number Membrane Resistance 
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Copyright information

© Plenum Press, New York 1975

Authors and Affiliations

  • E. Pull
    • 1
  1. 1.Centre de Recherche en Sciences NeurologiquesUniversité de MontréalMontréal 101Canada

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