Studies on Pain

Abstract

Analgesic efficiency of various drugs including morphine, codeine, and demerol is estimated by observing fingertip blood flow and variations in threshold value of a noxious stimulus which will produce finger-tip vasoconstriction following the subcut. injn. of the drug. Vaso-constriction is measured plethysmographically using strain gage tambour, blood flow by conventional venous occlusion methods. The noxious stimulus is a condenser discharge ranging from 0 to 92 volts in 23 steps delivered through 2 hypodermic needle electrodes inserted intracut. in the dorsum of the foot. An auditory adaptation stimulus is delivered at 8-sec. intervals, and all expts. are carried out in a constant temp., constant humidity, soundproof room. Analgesic drugs elevate the threshold value of noxious stimulus required to produce vasoconstriction; figures for the duration and magnitude of this effect are presented. Admn. of analgesics results in an increase in absolute blood flow and decrease in the degree of vasoconstriction elicited by a noxious stimulus of supra-threshold intensity.