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Role of the medial medullary reticular formation in relaying vestibular signals to the diaphragm and abdominal musclesChanges in posture can affect the resting length of respiratory muscles, requiring alterations in the activity of these muscles if ventilation is to be unaffected. Recent studies have shown that the vestibular system contributes to altering respiratory muscle activity during movement and changes in posture. Furthermore, anatomical studies have demonstrated that many bulbospinal neurons in the medial medullary reticular formation (MRF) provide inputs to phrenic and abdominal motoneurons; because this region of the reticular formation receives substantial vestibular and other movement-related input, it seems likely that medial medullary reticulospinal neurons could adjust the activity of respiratory motoneurons during postural alterations. The objective of the present study was to determine whether functional lesions of the MRF affect inspiratory and expiratory muscle responses to activation of the vestibular system. Lidocaine or muscimol injections into the MRF produced a large increase in diaphragm and abdominal muscle responses to vestibular stimulation. These vestibulo-respiratory responses were eliminated following subsequent chemical blockade of descending pathways in the lateral medulla. However, inactivation of pathways coursing through the lateral medulla eliminated excitatory, but not inhibitory, components of vestibulo-respiratory responses. The simplest explanation for these data is that MRF neurons that receive input from the vestibular nuclei make inhibitory connections with diaphragm and abdominal motoneurons, whereas a pathway that courses laterally in the caudal medulla provides excitatory vestibular inputs to these motoneurons.
Document ID
20040112429
Document Type
Reprint (Version printed in journal)
Authors
Mori, R. L. (University of Pittsburgh Pittsburgh, PA 15213, United States)
Bergsman, A. E.
Holmes, M. J.
Yates, B. J.
Date Acquired
August 21, 2013
Publication Date
May 25, 2001
Publication Information
Publication: Brain research
Volume: 902
Issue: 1
ISSN: 0006-8993
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: DC03732
CONTRACT_GRANT: EY08098
CONTRACT_GRANT: DC03417
CONTRACT_GRANT: DC00693
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Neuroscience