The time course of cellular responses to iontophoretically applied drugs

Abstract

Explicit expressions are derived giving a measure of the time course of responses to iontophoretic application of drugs or neurotransmitters. Cases treated include receptors on a line, a plane, and a sphere, effect of membrane capacitance, and binding of the drug to a surface, all of which give responses slower than those predicted on the usual “point receptor” assumption. Chemical reaction, for instance hydrolysis of the drug in the medium or on a surface, tends to shorten responses. Threshold and saturation non-linearities are also considered. It is concluded that agreement of experimental results with the “point receptor” time course is rather unlikely, although discrepancies will be masked if the distance between the iontophoretic source and the tissue is not measured but estimated from the responses.