The role of the intensity of low frequency electroacupuncture stimulation on the modulation of capsaicin-induced edema in the rat paw. A blind controlled study.

Experimental animal and clinical human data suggest that electroacupuncture (EAP) reduces the release of substance P from sensitive neurons, both at medullar level and in the periphery. Aim of our study is to verify the effect of different intensities of stimulation on edema induced by subcutaneous administration of capsaicin. The study was performed on 72 male Sprague-Dawley rats divided into 4 experimental groups according to the intensity of electrostimulation (5, 10, 50, 70 mA) and a control group. A constant current electrical stimulator delivering positive and negative biphasic wave (duration of one pulse wave complex: 500 microsec; pulse repetition rate: 5/sec) has been used for the stimulation. The lowest intensity of stimulation (5 mA) was effective in the prevention of neurogenic edema. Conversely, higher stimulation intensities, namely 10 and 50 mA, were not effective in reducing edema. Stimulation at 70 mA caused a worsening of edema, probably due to an increased release of substance P in the paw.