Central neural stimulation of respiration by sodium salicylate

Phrenic nerve responses to intravenous administration of sodium salicylate were measured in anesthetized, paralyzed cats whose vagi and carotid sinus nerves had been cut. Three groups of animals were studied. One consisted of animals with intact central nervous systems. The other two were identical except that the spinal cords had been transected at either T4-T5 or C7-T1. Salicylate led to a significant increase in respiration and whole body metabolism in all three groups. Transection of the spinal cord had no effect on the magnitude of the respiratory response to salicylate. We also studied another group of animals in which salicylate was injected directly into the third cerebral ventricle. This led to a significant increase in respiration without an increase in whole body metabolism. We conclude that salicylate stimulates respiration by a mechanism other than one related to its ability to increase whole body metabolism and that this mechanism is located within the central nervous system.