HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 287/2/R411    most recent 00019.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Verner, T. A. Articles by Pilowsky, P. M. Search for Related Content PubMed PubMed Citation Articles by Verner, T. A. Articles by Pilowsky, P. M.

ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

A mapping study of cardiorespiratory responses to chemical stimulation of the midline medulla oblongata in ventilated and freely breathing rats

Hypertension and Stroke Research Laboratories, Departments of Physiology and Neurosurgery, University of Sydney, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia

Submitted 12 January 2004 ; accepted in final form 16 March 2004

The aim of this study was to examine the cardiorespiratory effects of chemically stimulating neurons in the midline medulla oblongata (MM) of artificially ventilated and freely breathing anesthetized rats. Earlier studies reported that stimulation of the MM elicits increases or decreases in mean arterial pressure (MAP) and phrenic nerve activity, depending on the mode and site of stimulation, anesthetic, and species. In the first series of experiments, rats were anesthetized with urethane, artificially ventilated, paralyzed, and bilaterally vagotomized. The rostrocaudal extent of the MM was mapped by microinjections of DL-homocysteic acid or L-glutamate (both 100 mM, 100 nl), and, in line with previous studies, most injections produced only small responses in MAP, heart rate, and splanchnic sympathetic nerve activity. Increases in respiratory parameters were evoked in caudal regions. However, activation of a discrete region of the MM at the level of the caudal pole of the facial nucleus (CP7) consistently caused a dramatic reduction in phrenic nerve amplitude and/or frequency and, in six rats, produced a prolonged apnea. The second series of experiments was carried out on freely breathing pentobarbitone sodium-anesthetized rats, with a diaphragmatic electromyogram used to monitor respiratory activity. Respiratory activity could again be abolished at CP7 after microinjections of glutamate (100 mM, 50 nl); however, these responses were accompanied by large decreases in MAP and moderate reductions in heart rate. This depression of respiratory activity may be due to activation of propriobulbar inhibitory neurons that project to known respiratory centers in the brain stem.

medullary raphe nuclei; apnea; chemosensitivity

This article has been cited by other articles:

				J. Zhuang, F. Xu, and D. T. Frazier Hyperventilation evoked by activation of the vicinity of the caudal inferior olivary nucleus depends on the fastigial nucleus in anesthetized rats J Appl Physiol, May 1, 2008; 104(5): 1351 - 1358. [Abstract] [Full Text] [PDF]

				P. Mason, K. Gao, and J. R. Genzen Serotonergic Raphe Magnus Cell Discharge Reflects Ongoing Autonomic and Respiratory Activities J Neurophysiol, October 1, 2007; 98(4): 1919 - 1927. [Abstract] [Full Text] [PDF]

				L. A. Henderson, P. M. Macey, C. A. Richard, M. L. Runquist, and R. M. Harper Functional magnetic resonance imaging during hypotension in the developing animal J Appl Physiol, December 1, 2004; 97(6): 2248 - 2257. [Abstract] [Full Text] [PDF]