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An in vitro study of neural and myogenic control of human tracheal smooth muscle was undertaken. Over 80% of these had active tension and 13% had phasic contractile activity. Tonic and phasic activities were not reversed by indomethacin, 5,8,11,14-eicosatetraynoic acid, methysergide, mepyramine, atropine, or tetrodotoxin (TTX) but were blocked by the calcium antagonist verapamil. In some quiescent strips, tonic and/or phasic activity was induced by exposure to potassium-conductance blockers such as 4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA). Electrical (field) stimulation resulted in frequency-dependent biphasic responses: an initial atropine-sensitive cholinergic contraction followed by a nonadrenergic relaxation. This biphasic response to low stimulus parameters (less than 0.5 ms, less than 15 Hz) was blocked by TTX and scorpion venom and enhanced by 4-AP and TEA, consistent with a neural mechanism. Relaxation responses to longer pulse durations (0.5-1 ms) were not blocked by TTX despite abolition of contraction nor were they enhanced by 4-AP and TEA, suggesting a nonneural mechanism. ATP, adenosine, arachidonate metabolites, histamine, 5-hydroxytryptamine, neurotensin, or vasoactive intestinal polypeptide were ruled out as possible nonadrenergic mediators. The nature and physiological significance of the nonneural inhibitory response remains unknown.
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
March 1991,
The American review of respiratory disease,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
March 2006,
Toxicology and industrial health,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
October 1987,
The American review of respiratory disease,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
October 1987,
The American review of respiratory disease,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
June 1977,
The American review of respiratory disease,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
January 1988,
Tissue & cell,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
January 1993,
Romanian journal of physiology : physiological sciences,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
August 1994,
Journal of pharmacological and toxicological methods,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
January 1974,
Annals of the New York Academy of Sciences,
C Davis, and
M S Kannan, and
T R Jones, and
E E Daniel
January 1984,
International archives of allergy and applied immunology,
