The intracutaneous stimulus: a new pain model for algesimetric studies.

An intracutaneous pain stimulus is described for psychophysiological studies in man, which can easily be applied and which elicits highly reliable pain reactions in sessions repeated on different days, as well as in long-lasting sessions within a single day. The common electrical skin stimulation technique was modified by producing a circumscribed reduction in skin resistance under the stimulating electrode. A standardized procedure is described to reproducibly reduce this resistance by a factor of about 0.1 in a defined skin area of 1 sqmm. After this procedure, a definite and clear pain sensation could be elicited by current pulses which did not cause any sensation when conventionally applied. The reproducibility of pain reactions (pain ratings and late cerebral potentials) was tested in single sessions lasting up to 8 hours, as well as in weekly repeated experiments. First examples for applying these stimuli in algesimetric studies are given by double blind experiments with meperidine.