Document Detail

Differential sensitivity to bradykinin of esophageal distension-sensitive mechanoreceptors in vagal and sympathetic afferents of the opossum.
MedLine Citation:
PMID:  1432067     Owner:  NLM     Status:  MEDLINE    
1. Single-unit activity was recorded from afferent fibers in the cervical vagus and thoracic sympathetic nerves in the opossum. Seventy-six fibers that responded to balloon distension (100 mmHg for 10 s) of the smooth muscle portion of the esophagus were selected for further study. 2. Forty-nine distension-sensitive afferents were identified in the vagus nerve. The stimulus response function (SRF) of 41 fibers behaved as "low-threshold mechanoreceptors" (LTM), with mean threshold value of 0.29 +/- 0.17 mmHg and saturation pressure of 50-70 mmHg. All fibers demonstrated background activity, with a mean rate of 8.83 +/- 0.93 imp/s (range 0.5-31.25). 3. Twenty-seven distension-sensitive afferents were identified in the thoracic sympathetic chain (T6-T8) and splanchnic nerve. The SRF study revealed two types of fibers: 1) a wide-dynamic-range mechanonociceptor (WDRMN) with a mean response threshold of 3.43 +/- 0.90 mmHg (n = 15) and 2) a "high-threshold mechanonociceptor" (HTMN) with a mean response threshold of 34.93 +/- 2.70 mmHg (n = 12). The mean background activities of WDRMN and HTMN fibers were 0.5 +/- 0.13 and 0.20 +/- 0.08 imp/s, respectively. Both of these fibers had saturation pressures of > 120 mmHg. 4. The conduction velocities were measured in 14 LTM, 10 WDRMN, and seven HTMN fibers. The mean conduction velocity of LTM fibers was 5.03 +/- 1.35 m/s (range 0.97-18.00), with five unmyelinated "C"-fibers (< 2.5 m/s) and nine A-delta fibers (> 2.5 m/s). The mean conduction velocity of WDRMN fibers was 3.64 +/- 0.84 m/s (range 1.10-8.25), consisting of five C-fibers and five A-delta fibers. The mean conduction velocity of HTMN fibers was 6.22 +/- 2.35 m/s (range 1.73-24.66); three fibers were unmyelinated C-fibers, and four fibers were A-delta fibers. 5. The sensitivity to bradykinin (BK) administered systemically (1-300 micrograms/kg) was tested in LTM (n = 34), WDRMN (n = 15), and HTMN (n = 8) fibers. Twenty-six (66%) LTM fibers responded to BK, and eight (34%) fibers were insensitive to BK. All 15 WDRMN and eight HTMN fibers tested responded to BK. 6. Tachyphylaxis to repeated application of BK was tested in all three classes of fibers. The vagal LTM fibers did not exhibit tachyphylaxis when BK was given at an intervals of 10 min. The sympathetic WDRMN and HTMN fibers demonstrated partial tachyphylaxis when BK was injected at 10-min intervals, but not when BK was injected at 20-min intervals.(ABSTRACT TRUNCATED AT 400 WORDS)
J N Sengupta; J K Saha; R K Goyal
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  68     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  1992 Oct 
Date Detail:
Created Date:  1992-12-17     Completed Date:  1992-12-17     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1053-67     Citation Subset:  IM; S    
Charles A. Dana Research Institute, Beth Israel Hospital, Harvard Medical School, Boston, Massachusetts 02215.
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MeSH Terms
Action Potentials / drug effects
Afferent Pathways / drug effects,  physiology*
Axons / drug effects,  physiology
Bradykinin / analogs & derivatives*,  antagonists & inhibitors,  pharmacology*
Carbachol / pharmacology
Esophagus / innervation*
Mechanoreceptors / drug effects,  physiology*
Muscle Contraction / physiology*
Muscle, Smooth / innervation
Nerve Fibers / drug effects,  physiology*
Neural Conduction / drug effects
Sympathetic Nervous System / drug effects,  physiology*
Vagus Nerve / drug effects,  physiology*
Grant Support
Reg. No./Substance:
51-83-2/Carbachol; 58-82-2/Bradykinin

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

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