Potential differences in the inferior vena cava and between cava and extravascular electrode at leg contraction in man.

When a voluntary adult male contracted his leg muscles, electric potential differences were recorded between platinum electrodes positioned inside the vena cava or between the vena cava and the grounded skin. Two experiments confirm that potential differences at leg contractions in man have a similar appearance as those in the rat at pain-evoked contractions of leg muscles. Platinum electrodes were used in man. The potential differences obtained are thereafter compared with recordings with Ag-AgCl electrodes in salt-bridges in the rat. Slow potential waves with superimposed irregular potential oscillations are recorded in man as previously found in the rat using platinum or Ag-AgCl electrodes. The findings indicate that vascular-interstitial routes participate in a vascular-interstitial-neuromuscular closed circuit, which is activated at contraction of the muscles.