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: Effects of vagotomy on ventilatory responses to CO2 in alligators.
    Author: Douse MA, Mitchell GS.
    Journal: Respir Physiol; 1992 Jan; 87(1):63-76. PubMed ID: 1313182.
    Abstract:
    Reptiles increase ventilation during hypercapnia at a constant temperature. In this study, the contributions of vagal vs non-vagal receptors to CO2 ventilatory responses were investigated in 16 sedated Alligator mississippiensis (25 mg/kg pentobarbital; 3 days prior to data collection). Four animals served as controls to assess the effects of time and/or anesthetic drift on ventilation and blood gases; significant ventilatory drift was not detected during the observation period. The effects of bilateral vagotomy on CO2 ventilatory responses were determined during spontaneous breathing (n = 6) and unidirectional ventilation (UDV; n = 6) at two body temperatures (Tb = 30 and 20 degrees C). Resting PaCO2, minute ventilation (VI), tidal volume (VT) and breathing frequency (f) were elevated at 30 degrees C relative to 20 degrees C in spontaneously breathing alligators. Increasing inspired CO2 to 5% increased PaCO2, f, VT and VI at both levels of Tb. Ventilatory sensitivity to CO2 (S = delta VI/delta PaCO2) was higher at 30 degrees C with a temperature coefficient (Q10) of 2.3. Vagotomy increased PaCO2 and VT, decreased f and had no effect on VI at either Tb. After vagotomy, hypercapnia had no effects on ventilation. When CO2 feedback loops were opened by UDV at a high flow rate (greater than 2 L/min), Tb had no effects on ventilatory efforts at constant PCO2, but hypercapnia significantly increased f, VT and VI. S was variable with a Q10 of 2.1. After vagotomy, a significant CO2-ventilatory response remained during UDV, but S was unaffected by Tb (Q10 = 0.8). The results indicate that non-vagal chemoreceptors contribute to CO2 ventilatory responses in alligators, although their contribution following vagotomy is evident only during unidirectional ventilation. Although tentative, the data also suggest that CO2-sensitive vagal receptors may be necessary for the temperature dependency of S.
    [Abstract] [Full Text] [Related] [New Search]