Electrophysiological aspects of reflexogenic area in the chelonian, Geoclemmys reevesii.

Electrophysiological and anatomical experiments were performed to determine the baro- and chemoreceptive area of the turtle, Geoclemmys reevesii. The baro- and chemoreceptive sites are located in the aortic and pulmonary arches and the truncal region. The aortic arch is innervated by both the superior truncal nerve (aortic nerve) and a branch of the inferior truncal nerve arising from the ganglion trunci of the vagus. The pulmonary arch is innervated by a fine branch of the inferior truncal nerve, a branch containing mainly barosensitive and a few chemosensory fibers. On the peripheral cut end of these nerves, afferent electrical baro- and chemosensory activities were induced by NaCN and hyperoxia. Fluorescence microscopy revealed that the glomus cells are located in these regions.