Conditions affecting rate of development of anoxic block in C fibers

¹ Laboratoire de Physiologie Générale, Faculté des Sciences, Université de Paris, Paris, France; and Department of Physiology, Washington University School of Medicine, St. Louis, Missouri

The isolated splenic nerve of sheep conducted impulses for an average of 10 minutes in the complete absence of oxygen at 37.5°C. If, immediately following conduction failure, the nerve was allowed to recuperate for 2 hours in oxygen it became able to conduct impulses as long during a repeated period of anoxia as it had initially. If the initial period of anoxia was prolonged beyond 28 minutes the nerve sustained irreversible damage and its ability to conduct impulses during subsequent periods of anoxia was shortened proportionally. For recuperation periods shorter than 2 hours the conduction block during the course of the second period of anoxia appeared earlier. Temperatures below 37.5°C or CO₂ concentrations above 10% prolonged the time to conduction block during anoxia; temperatures above 37.5°C or frequencies of stimulation greater than 1/sec. shortened the time to conduction block during anoxia.