These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Inhibitory and excitatory responses to field stimulation in fetal and adult pig airway.
    Author: Mitchell HW, Sparrow MP, Tagliaferri RP.
    Journal: Pediatr Res; 1990 Jul; 28(1):69-74. PubMed ID: 2377398.
    Abstract:
    The innervation in airway tissues from young adult (15-26 wk) and fetal (95/115 d gestation) pigs was compared in isolated tracheal and bronchial preparations subjected to electrical field stimulation. End-organ responsiveness to carbachol, substance P, isoprenaline, and VIP was present by 95 d gestation. Electrical field stimulation (0.5-20 Hz, 70 V, 0.5 ms) resulted in a frequency-dependent contraction that was blocked by atropine (10(-6) M) and TTX (10(-6) M) at both ages. However, there was a 10-fold increase in threshold in the fetal airways because contractions were evoked at frequencies of approximately 5 Hz in the fetus compared with 0.5 Hz in the young adult airways. In the young adult airways, there were atropine-resistant contractions at longer pulse durations (1-5 ms, 20 Hz), but not usually in the fetus. The atropine-resistant contractions were not blocked by TTX. Capsaicin (10(-6) M) produced no contraction in the pig airway. In tissues contracted using the ED50 of carbachol, electrical stimulation (1-20 Hz, 70 V, 1 ms) caused marked relaxation, however, compared with those in the young adult, fetal responses were weak or absent. Propranolol (10(-6) M) partially reduced the relaxation of the young adult bronchus (approximately 25%), but it had little effect on responses in the other young adult and fetal preparations. Therefore, the inhibitory innervation of pig airways was predominantly nonadrenergic and the excitatory component was cholinergic. Neither of these components was fully developed in the fetus close to term.
    [Abstract] [Full Text] [Related] [New Search]