Journal of Applied Physiology, Vol 59, Issue 4 1201-1207, Copyright © 1985 by American Physiological Society

ARTICLES

Responses of bulbospinal and laryngeal respiratory neurons to hypercapnia and hypoxia

W. M. St John and A. L. Bianchi

The purpose was to evaluate activities of medullary respiratory neurons during equivalent changes in phrenic discharge resulting from hypercapnia and hypoxia. Decerebrate, cerebellectomized, paralyzed, and ventilated cats were used. Vagi were sectioned at left midcervical and right intrathoracic levels caudal to the origin of right recurrent laryngeal nerve. Activities of phrenic nerve and single respiratory neurons were monitored. Neurons exhibiting antidromic action potentials following stimulations of the spinal cord and recurrent laryngeal nerve were designated, respectively, bulbospinal or laryngeal. The remaining neurons were not antidromically activated. Hypercapnia caused significant augmentations of discharge frequencies for all neuronal groups. Many of these neurons had no change or declines of activity in hypoxia. We conclude that central chemoreceptor afferent influences are ubiquitous, but excitatory influences from carotid chemoreceptors are more limited in distribution among medullary respiratory neurons. Hypoxia will increase activities of neurons that receive sufficient excitatory peripheral chemoreceptor afferents to overcome direct depression by brain stem hypoxia. The possibility that responses of respiratory muscles to hypoxia are programmed within the medulla is discussed.

This article has been cited by other articles:

				A. T. Lovering, J. J. Fraigne, W. L. Dunin-Barkowski, E. H. Vidruk, and J. M. Orem Medullary Respiratory Neural Activity During Hypoxia in NREM and REM Sleep in the Cat J Neurophysiol, February 1, 2006; 95(2): 803 - 810. [Abstract] [Full Text] [PDF]

				A. K. Tryba and J.-M. Ramirez Response of the Respiratory Network of Mice to Hyperthermia J Neurophysiol, June 1, 2003; 89(6): 2975 - 2983. [Abstract] [Full Text] [PDF]

				S.-Y. Zhou, G. J. Basura, and H. G. Goshgarian Serotonin2 receptors mediate respiratory recovery after cervical spinal cord hemisection in adult rats J Appl Physiol, December 1, 2001; 91(6): 2665 - 2673. [Abstract] [Full Text] [PDF]

				M. Tonkovic-Capin, E. J. Zuperku, E. A. Stuth, J. Bajic, Z. Dogas, and F. A. Hopp Effect of central CO2 drive on lung inflation responses of expiratory bulbospinal neurons in dogs Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2000; 279(5): R1606 - R1618. [Abstract] [Full Text] [PDF]

				M. Thoby-Brisson and J.-M. Ramirez Role of Inspiratory Pacemaker Neurons in Mediating the Hypoxic Response of the Respiratory Network In Vitro J. Neurosci., August 1, 2000; 20(15): 5858 - 5866. [Abstract] [Full Text] [PDF]

				P. Telgkamp and J.-M. Ramirez Differential Responses of Respiratory Nuclei to Anoxia in Rhythmic Brain Stem Slices of Mice J Neurophysiol, November 1, 1999; 82(5): 2163 - 2170. [Abstract] [Full Text] [PDF]

				M. Krolo, E. A. Stuth, M. Tonkovic-Capin, Z. Dogas, F. A. Hopp, D. R. McCrimmon, and E. J. Zuperku Differential Roles of Ionotropic Glutamate Receptors in Canine Medullary Inspiratory Neurons of the Ventral Respiratory Group J Neurophysiol, July 1, 1999; 82(1): 60 - 68. [Abstract] [Full Text] [PDF]

				J. M. Ramirez, U.J.A. Quellmalz, and B. Wilken Developmental Changes in the Hypoxic Response of the Hypoglossus Respiratory Motor Output In Vitro J Neurophysiol, July 1, 1997; 78(1): 383 - 392. [Abstract] [Full Text] [PDF]