Journal of Applied Physiology, Vol 60, Issue 2 391-397, Copyright © 1986 by American Physiological Society
Responses of ganglioglomerular nerve activity to respiratory stimuli in the cat
S. Lahiri, S. Matsumoto and A. Mokashi
We studied the responses of the ganglioglomerular nerve (GGN) efferents to
brief periods of hypoxia and hypercapnia and to several levels of
steady-state arterial PO2 and PCO2 and to intravascular injection of
cyanide in thirteen anesthetized cats. The cats breathed spontaneously. A
branch of the GGN which was cut close to the carotid body was divided into
several filaments, and the activity of each filament was tested until clean
and identifiable action potentials were obtained. The GGN efferent
activity, breath-by-breath inspiratory volume, tracheal PO2 and PCO2 and
arterial blood pressure were recorded simultaneously. We found that the GGN
contained spontaneously active fibers which showed a range of responses to
the respiratory stimuli. Fifty-eight percent of the filaments with dominant
cardiovascular rhythm showed the least response to blood gas stimuli.
Forty-two percent showed clear responses to hypoxia and hypercapnia. These
responses developed slowly with the onset of the stimulus but decreased
promptly with the withdrawal of the stimulus. These GGN efferents were also
promptly stimulated by sodium cyanide. The steady-state response curve to
hypoxia was hyperbolic and to hypercapnia it was linear. Some of these
fibers showed stronger respiratory rhythms than others. The responses of
these GGN efferents were associated with the respiratory responses to
hypoxia and hypercapnia. For the same respiratory drive, however, the
steady-state hypoxic stimulus elicited a greater GGN response than did
hypercapnia.
