Chemoceptor reflexes in swine

Respiratory reflexes originating from chemoceptors in the carotid body have not been previously demonstrated in swine. These investigations indicate the carotid sinus areas of pigs possess chemoceptors sensitive to potassium cyanide and lobeline. Stimulation of these chemoceptors causes a reflex stimulation of the respiratory center and hyperpnea. The sensitivity of the chemoceptors to potassium cyanide is apparently enhanced by vagotomy, whereas this procedure does not reduce the threshold to lobeline. Intravenous injections of cyanide reflexly stimulate the respiratory center if one or both carotid sinus areas are intact. Following bilateral vagotomy and denervation of the chemoceptors in the carotid sinus regions, no respiratory response is elicited by intravenous injections of potassium cyanide.