Contribution of carotid chemoreceptors to mesenteric venoconstriction during acute hypercapnia in rabbits.
The contribution of carotid chemoreceptors to hypercapnia-induced mesenteric venoconstriction was examined in 12 alpha-chloralose-anesthetized rabbits (1.0-1.6 kg). Surgical preparation consisted of a tracheotomy, femoral arterial and venous cannulation, and a midline laparotomy through which a 13-cm loop of ileum was exteriorized and superfused with physiological salt solution. Mesenteric vein diameter and intravenous pressure (using a servo-null measurement system) were measured in 500- to 1,000-micron mesenteric veins during 40-s periods of 15%, 20%, and 25% CO2 inhalation. Measurements were then repeated following bilateral ablation of the carotid chemoreceptors. Before denervation, mesenteric vein diameter constricted 6.5 +/- 1.1%, 11.9 +/- 1.1%, and 17.9 +/- 2.2% during the 15%, 20%, and 25% CO2 inhalation, respectively. After denervation, these values were reduced to 5.0 +/- 0.9%, 6.9 +/- 1.2%, and 8.4 +/- 1.3%, respectively. We conclude that activation of the carotid chemoreceptors by hypercapnia induces active mesenteric venoconstriction. After denervation of the carotid baroreceptors and chemoreceptors, there was also a small decrease in venule diameter proportional to the level of inspired CO2. We further conclude that noncarotid body chemoreceptor activation contributes to mesenteric venular constriction.
Tominaga
M
M
Department of Anesthesiology, The Medical College of Wisconsin, Milwaukee 53226, USA.
Stekiel
T A
TA
Bosnjak
Z J
ZJ
Kampine
J P
JP
D000818:Animals; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood*; D002339:Carotid Arteries / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D004558:Electric Stimulation; D006339:Heart Rate; D006935:Hypercapnia; D007082:Ileum / Q000098:blood supply / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D008642:Mesenteric Veins / Q000502:physiology*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*
D002245:Carbon Dioxide