Cranial Nerve and Phrenic Respiratory Rhythmicity during Changes in Chemical Stimuli in the Anesthetized Rat
Central respiratory rhythmicity and/or timing has been determined by the trajectory of phrenic (Phr) nerve discharges. Cranial nerves innervating the upper airway muscles also display respiratory modulated activity synchronized with Phr activity. These cranial nerve motoneurons as well as spinal Phr motoneurons (or Phr driving medullary pre-motor neurons) are driven by a common rhythm generating mechanism. There are, however, significant differences in the discharge pattern and responses to chemical stimuli between Phr and cranial nerve respiratory activity1. The onset of inspiratory activity of the cranial nerves is much earlier than that of Phr nerve2, 3, 4. Changes in chemical stimuli (Pao2, Paco2) initiate differential effects on I activity among various respiratory nerves, including Phr and cranial nerves3, 5, 6, 7. On the other hand, cranial nerve respiratory activities are sensitive to anesthesia and/or sleep stage, and hence have not been considered as major output signals for observation of central respiratory rhythmicity8, 9, 10. In the present experiment we found that the glossopharyngeal (IX) nerve I activity showed much smaller suppression during hypocapnia or hypoxia than the Phr I discharge did. Furthermore a small ramp-like rhythmic IX activity even without Phr burst was seen during hypocapnic or hypoxic respiratory suppression.
KeywordsCranial Nerve Recurrent Laryngeal Nerve Phrenic Nerve Chemical Stimulus Carotid Sinus Nerve
Unable to display preview. Download preview PDF.
- 1.C. Von Euler, On the central pattern generator for the basic breathing rhythmicity. J. Appl. Physiol. 55:1647(1983).Google Scholar
- 5.S. D. Iscoe, Central control of the upper airway, in: “Respiratory function of the upper airway”, O. P. Mathew and G. Sant’Ambriogio, eds., Marcel Dekker, New York-Basel (1988).Google Scholar
- 7.D. Zhou, Q. Huang, W.M. St. John, and D. Bartlett, Jr, Respiratory activities of intralaryngeal branches of the recurrent laryngeal nerve, J. Appl. Physiol. 67:1117(1989)Google Scholar
- 9.J.L. Feldman, Neurophysiology of breathing in mammals, in: “Handbook of physiology, sect. 1, The nervous system, Vol.1”, V. B. Mountcastle, F.E. Bloom, and S.R. Geiger, eds., Amer. Physiol. Soc., Bethesda, (1986).Google Scholar
- 10.Y. Murakami, and J.I. Kirchner, Respiratory activity of the external laryngeal muscles: an electromyographic study in the cat, in: “Ventilatory and phonatory control”, D. Wyke, ed., Oxford Univ. Press, London (1974).Google Scholar
- 15.Y. Fukuda, Differences in glossopharyngeal and phrenic inspiratory activities of rats during hypocapnia and hypoxia, Neurosci Lett. (1992)In press.Google Scholar
- 17.H. Ellenberger, and J.L. Feldman, Monosynaptic transmission of respiratory drive to phrenic motoneurons from brainstem bulbospinal neurons in rats, J. Comp. Physiol, 269:47(1988).Google Scholar
- 21.W.M.St. John, D. Bartlett, Jr, K.V. Knuth, and J.C. Hwang, Brain stem genesis of automatic ventilatory patterns independent of spinal mechanisms. J.Appl. Physiol. 51:204(1981).Google Scholar
- 22.J.C. Smith, J.J. Greer, G. Liu, and J.L. Feldman, Neural mechanisms generating respiratory pattern in mammalian brainstem-spinal cord in vitro. I Spatio-temporal patterns of motor and medullary neuron activity. J. Neurophysiol. 64:1149(1990).Google Scholar
- 23.S.W. Schwarzacher, Z. Wilhelm, K. Anders, and D.W. Richter, The medullary respiratory network in the rat. J. Physiol.(Lond.) 435:631(1991).Google Scholar