| Pregnancy increases excitability of mechanosensitive afferents innervating the uterine cervix. | |
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MedLine Citation:
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PMID: 18497610 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND: Labor pain derives primarily from stimulation of afferents innervating the uterine cervix and lower uterine segment. The authors have previously shown that the excitability of these afferents is regulated by sex hormones and test in this study whether pregnancy also alters their excitability. METHODS: After animal care committee approval, Sprague-Dawley rats (nonpregnant, pregnant days 17 and 21) were anesthetized, and two metal rods were placed through the cervix for distension. The right hypogastric nerve was dissected and carefully teased until recording from a single unit was obtained. Spontaneous activity and the response to a graded distension (20-80 g) were recorded for off-line analysis. RESULTS: A total of 151 fiber units were recorded. Pregnancy was associated with an increase in spontaneous nerve activity in the absence of a mechanical stimulus (median of 0.98 and 1.56 Hz from pregnant days 17 and 21, respectively, compared with 0.45 Hz in nonpregnant; P < 0.01). The proportion of fibers responding to the weakest stimulus (20 g) was significantly greater in pregnant than in nonpregnant animals. The response to graded distension differed significantly among groups, with day 21 > day 17 > nonpregnant. CONCLUSIONS: Afferents that innervate the uterine cervix sprout into this tissue during late pregnancy, and estrogen increases excitability of these mechanosensitive afferents. Here, the authors show that excitability also increases during pregnancy. These data suggest that, close to the onset of labor, there is an increased input to the spinal cord from cervical distension and an increased depolarization of afferent terminals in the cervix, effects that could influence pain and the progress of labor. |
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Authors:
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Baogang Liu; Chuanyao Tong; James C Eisenach |
Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural |
Journal Detail:
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Title: Anesthesiology Volume: 108 ISSN: 1528-1175 ISO Abbreviation: Anesthesiology Publication Date: 2008 Jun |
Date Detail:
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Created Date: 2008-05-23 Completed Date: 2008-06-17 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 1300217 Medline TA: Anesthesiology Country: United States |
Other Details:
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Languages: eng Pagination: 1087-92 Citation Subset: AIM; IM |
Affiliation:
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Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1009, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials
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physiology Afferent Pathways / physiology* Animals Cervix Uteri / innervation* Female Hypogastric Plexus / physiology Neurons, Afferent / physiology* Physical Stimulation / methods* Pregnancy Pregnancy, Animal / physiology* Rats Rats, Sprague-Dawley Time Factors |
| Grant Support | |
ID/Acronym/Agency:
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NS48065/NS/NINDS NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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