Ventilatory Responses of Rats to Electrical Stimulation in CO₂ Containing Atmospheres

¹ From the Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Steady state measurements of metabolic gas exchange, ventilation and body temperature were made in anesthetized (urethane) Wistar rats breathing gas mixtures in compositions ranging from 20 to 30% oxygen, 0 to 10% carbon dioxide, and nitrogen. Metabolic rate was caused to vary by interrupted electrical stimulation of limb muscles. From 218 such determinations a regression was calculated, V_coco2 = 0.00843 V (0.999Fe – Fi) – 0.091. It is concluded that the _coco2 exchange of rats is similar to those reported in man and dog. Particular care was taken to assure a steady (constant) state at the time of measurement. Homeostatic defense against internally produced CO₂ is good, whereas that against environmental CO₂ changes is poor.