1966 Volume 88 Issue 2 Pages 103-116
Chemoreceptor function and reflex activity of the carotid labyrinth of the toad were electroneurographically investigated. An additional attempt was made to identify chemoreceptor cells histologically. In the carotid nerve, the emission of chemoreceptor impulses together with baroreceptor ones was confirmed. The latter were discharged only by a rise in blood pressure, while the former were discharged spontaneously and at random. In perfusion experiments, lobeline, sodium cyanide and oxygen lack were found to increase the chemosensory activity. The chemoreceptor stimulations caused an excitation of respiration, indicating that the carotid labyrinth plays an important role in the regulation of respiration in the toad.
In small portions of the carotid labyrinth which were still able to send the impulses to the carotid nerve, there was confirmed the existence of a small number of special cells located in the vicinity of small blood vessels, which resembled in structure the mammalian carotid body cells.