Abstract

In in situ saline-perfused cat spleen, recordings of the electrical activities of the splelnic nerve were taken concomitantly with collections of splenic perfusate for assay for norepinephrine. Electrophysiological observations indicated that the cat splenic nerve was composed mainly of C-fibers conducting at a velocity of 0.59±0.05 m/sec. Unlike events in blood-perfused cat spleen, in the saline-perfused spleen the compound action potential of the splenic nerve progressively declined in amplitude upon repetitive stimulation. The decline was due to refractoriness of the splelnic nerve. In comparison with an ideal state having a constant response with repeated stimulation, the total electrical activity after about 200 stimuli at 10/sec stimulation was 0.94 whereas at 30/sec stimulation it was only 0.59. The norepinephrine overflow at 10/sec stimulation was larger than that at 30/sec and the ratio of the overflows at the two frequencies was in quantitative agreement with the ratio of the total electrical activities at these frequencies. If the stimulating current was not carefully isolated from ground to prevent stray current from spreading into tissues other than the splenic nerve, norepinephrine overflow was likely to be spuriously high. Tetrodotoxin in minimally hypotensive doses did not block splenic nerve activity nor did it interfere with the release of norepinephrine.