Document Detail

Benzodiazepines acting on ventral surface of medulla cause airway dilation.
MedLine Citation:
PMID:  2508497     Owner:  NLM     Status:  MEDLINE    
The benzodiazepines that have anxiolytic, anticonvulsant, muscle-relaxant, and sedative-hypnotic properties affect respiration possibly by acting on gamma-aminobutyric acid (GABA)ergic receptors. This study investigated the effects of benzodiazepines diazepam and midazolam) applied topically to or microinjected just beneath the ventrolateral medullary surface (VMS) on airway tone in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated cats. Trachealis smooth muscle tension was assessed by measuring the changes in pressure in a balloon placed in a bypassed rostral segment of the trachea. In 21 cats ventilated with 7% CO2 in O2, surface application of benzodiazepines caused a significant decrease in tracheal tone. Similar to topical application, microinjection of midazolam (1 microgram) in the ventral medulla (0.1-0.2 mm from the surface) in six cats decreased tracheal pressure by 13.2 +/- 2.1 cmH2O (P less than 0.01). In addition, application of benzodiazepines on the VMS in animals ventilated with 12% O2 in N2 (n = 5) decreased tracheal pressure from 15.9 +/- 2.2 to 5.2 +/- 2.7 cmH2O (P less than 0.05). Furthermore, in all cats studied (n = 6), the magnitude of lung deflation-induced tracheal contraction was reduced after application of benzodiazepines on the ventral surface of the medulla (from 11.4 +/- 1.6 to 2.2 +/- 0.9 cmH2O; P less than 0.01). The effects of benzodiazepines on tracheal tone were reversed and blocked by application of Ro 15-1788, a specific benzodiazepines antagonist. However, when parasympathetic activity was abolished by atropine and tracheal tone was restored with 5-hydroxytryptamine, benzodiazepines applied on the VMS had no effect on tracheal pressure. These results suggest that benzodiazepines acting centrally, on structures located near the VMS, can cause a decrease in airway smooth muscle tone by diminishing the activity of parasympathetic neurons which project to the airways.
M A Haxhiu; E van Lunteren; N S Cherniack; E C Deal
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  257     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1989 Oct 
Date Detail:
Created Date:  1989-11-17     Completed Date:  1989-11-17     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R810-5     Citation Subset:  IM    
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
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MeSH Terms
Atropine / pharmacology
Blood Pressure / drug effects
Diazepam / pharmacology*
Flumazenil / pharmacology*
Lung / physiology
Medulla Oblongata / drug effects,  physiology*
Midazolam / pharmacology*
Muscle Relaxation / drug effects
Muscle, Smooth / drug effects,  physiology*
Phrenic Nerve / physiology
Trachea / drug effects,  physiology*
Grant Support
Reg. No./Substance:
439-14-5/Diazepam; 51-55-8/Atropine; 59467-70-8/Midazolam; 78755-81-4/Flumazenil

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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