Reflex bronchial vasodilation in dogs evoked by injection of a small volume of water into a bronchus

Injection of water into a lobar bronchus stimulates airway C-fibers and rapidly adapting receptors and evokes airway defense reflexes. To determine whether this stimulus also evokes a reflex increase in bronchial blood flow (Qbr), we injected 1–2 ml of water into a lobar bronchus in anesthetized dogs. Injection decreased arterial pressure but increased Qbr from 9 +/- 1 to 21 +/- 3 ml/min. The increase had a latency of 6–8 s and reached a peak after approximately 20 s; Qbr returned to control after 60–90 s. Airway mucosal blood flow, measured by colored microspheres, increased in proportion to Qbr. In contrast, flow in an adjacent intercostal artery that did not supply the airway decreased slightly. Injection of isosmotic saline had little effect. In 13 of 16 dogs, the water-induced increase in Qbr was abolished by cutting or cooling the cervical vagus nerves and hence was entirely dependent on centrally mediated vagal pathways. When the vagus nerves were intact, about one-third of the vasodilator response remained after pharmacological blockade of muscarinic and adrenergic receptors. We conclude that in dogs the defense response to water in the lower airways includes a large increase in Qbr that is partly due to activation of nonadrenergic noncholinergic autonomic pathways.

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Dopamine-1 receptor stimulation impairs intestinal oxygen utilization during critical hypoperfusion

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00636.2002 ◽

2003 ◽

Vol 284 (2) ◽

pp. H668-H675 ◽

Cited By ~ 6

Author(s):

Jorge A. Guzman ◽

Ariosto E. Rosado ◽

James A. Kruse

Keyword(s):

Blood Flow ◽

Mucosal Blood Flow ◽

Control Group ◽

Oxygen Utilization ◽

Hemorrhage Control ◽

Receptor Stimulation ◽

Anesthetized Dogs ◽

Group 2 ◽

Increased Susceptibility ◽

Group 1

Effects of a dopamine-1 (DA-1) receptor agonist on systemic and intestinal oxygen delivery (D˙o 2)-uptake relationships were studied in anesthetized dogs during sequential hemorrhage. Control ( group 1) and experimental animals ( group 2) were treated similarly except for the addition of fenoldopam (1.0 μg · kg−1 · min−1) in group 2. Both groups had comparable systemic criticalD˙o 2(D˙o 2crit), but animals in group 2 had a higher gut D˙o 2crit(1.12 ± 1.13 vs. 0.80 ± 0.09 ml · kg−1 · min−1, P < 0.05). At the mucosal level, a clear biphasic delivery-uptake relationship was not observed in group 1; thus oxygen consumption by the mucosa may be supply dependent under physiological conditions. Group 2 demonstrated higher peak mucosal blood flow and lack of supply dependency at higher mucosalD˙o 2 levels. Fenoldopam resulted in a more conspicuous biphasic relationship at the mucosa and a rightward shift of overall splanchnic D˙o 2crit despite increased splanchnic blood flow. These findings suggest that DA-1 receptor stimulation results in increased gut perfusion heterogeneity and maldistribution of perfusion, resulting in increased susceptibility to ischemia.

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Effect of Irsogladine Maleate on NSAID-Induced Reduction of Gastric Mucosal Blood Flow in Anesthetized Dogs

Digestion ◽

10.1159/000206823 ◽

2009 ◽

Vol 79 (2) ◽

pp. 73-78 ◽

Cited By ~ 7

Author(s):

Motonori Sato ◽

Noriaki Manabe ◽

Jiro Hata ◽

Manabu Ishii ◽

Tomoari Kamada ◽

...

Keyword(s):

Blood Flow ◽

Mucosal Blood Flow ◽

Gastric Mucosal Blood Flow ◽

Irsogladine Maleate ◽

Anesthetized Dogs

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Pulmonary C-fibers reflexly increase secretion by tracheal submucosal glands in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.3.907 ◽

1985 ◽

Vol 58 (3) ◽

pp. 907-910 ◽

Cited By ~ 26

Author(s):

H. D. Schultz ◽

A. M. Roberts ◽

C. Bratcher ◽

H. M. Coleridge ◽

J. C. Coleridge ◽

...

Keyword(s):

Gland Secretion ◽

Right Atrial ◽

Vagus Nerves ◽

C Fibers ◽

Airway Secretion ◽

Submucosal Glands ◽

C Fiber ◽

Anesthetized Dogs ◽

The Right ◽

Stimulation Of

Stimulation of bronchial C-fibers evokes a reflex increase in secretion by tracheal submucosal glands, but the influence of pulmonary C-fibers on tracheal gland secretion is uncertain. In anesthetized dogs with open chests, we sprayed powdered tantalum on the exposed mucosa of a segment of the upper trachea to measure the rate of secretion by submucosal glands. Secretions from the gland ducts caused elevations (hillocks) in the tantalum layer. We counted hillocks at 10-s intervals for 60 s before and 60 s after we injected capsaicin (10–20 micrograms/kg) into the right atrium to stimulate pulmonary C-fiber endings. Right atrial injection of capsaicin increased the rate of hillock formation fourfold, but left atrial injection had no significant effect. The response was abolished by cutting the vagus nerves or cooling them to 0 degree C. We conclude that the reflex increase in tracheal submucosal gland secretion evoked by right atrial injection of capsaicin was initiated as capsaicin passed through the pulmonary vascular bed, and hence that pulmonary C-fibers, like bronchial C-fibers, reflexly increase airway secretion.

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Capsaicin-induced bronchial vasodilation in dogs: central and peripheral neural mechanisms

Journal of Applied Physiology ◽

10.1152/jappl.1993.74.1.259 ◽

1993 ◽

Vol 74 (1) ◽

pp. 259-266 ◽

Cited By ~ 18

Author(s):

T. E. Pisarri ◽

J. C. Coleridge ◽

H. M. Coleridge

Keyword(s):

Blood Flow ◽

Bronchial Artery ◽

Neutral Endopeptidase ◽

Right Atrial ◽

Vagus Nerves ◽

Vascular Effects ◽

Vascular Conductance ◽

Axon Reflex ◽

C Fibers ◽

The Right

In 21 anesthetized dogs, we placed a flow probe around the right bronchial artery and examined changes in bronchial blood flow and bronchial vascular conductance when pulmonary C-fibers were stimulated by right atrial injection of capsaicin. When vagus nerves were intact, capsaicin evoked a pulmonary depressor chemoreflex and increased bronchial blood flow by 125% and bronchial vascular conductance by 175%; flow in an adjacent intercostal artery did not increase. Injection of color-coded microspheres revealed that blood flow to mucosa of lower trachea and to a peripheral bronchus doubled, whereas flow to posterior tracheal wall increased little. Cooling (to -1 degree C) or cutting cervical vagi (in 17 dogs) abolished the pulmonary chemoreflex and abolished all bronchial vascular effects in nine dogs but 33% of the vasodilation persisted in eight. In five of six dogs, this persisting vasodilation was potentiated by phosphoramidon (a neutral endopeptidase inhibitor that retards breakdown of neuropeptides released by C-fibers). Atropine reduced the capsaicin-induced bronchial vasodilation by approximately 30%. We conclude that the bronchial vasodilation was largely due to a centrally mediated vagal reflex and that a neuropeptide-dependent axon-reflex component was also present in about one-half the dogs.

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Tracheal contraction and relaxation initiated by lung and somatic afferents in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.4.984 ◽

1982 ◽

Vol 52 (4) ◽

pp. 984-990 ◽

Cited By ~ 37

Author(s):

J. C. Coleridge ◽

H. M. Coleridge ◽

A. M. Roberts ◽

M. P. Kaufman ◽

D. G. Baker

Keyword(s):

Smooth Muscle ◽

Muscle Tension ◽

Right Atrial ◽

Vagus Nerves ◽

Apparent Contradiction ◽

C Fibers ◽

Somatic Afferents ◽

Anesthetized Dogs ◽

The Right ◽

Contraction And Relaxation

Capsaicin injected into the right heart of dogs causes reflex bronchoconstriction by stimulating pulmonary C-fibers, but injected into the left heart it is said to have little effect even though it stimulates bronchial C-fibers, which are known to cause contraction of airway smooth muscle. Attempting to resolve this apparent contradiction, we recorded smooth muscle tension in an innervated tracheal segment in anesthetized dogs and examined the reflex effects of injecting capsaicin intravascularly at different sites. Right atrial injection of capsaicin (10 micrograms/kg) caused tracheal contraction, as did bronchial arterial injection (0.15–5.0 micrograms); left atrial injection (10 micrograms/kg), however, caused relaxation or slight contraction, or a combination of the two. Contraction but not relaxation was abolished by cutting or cooling (0 degree C) the cervical vagus nerves. Femoral arterial injection (10–100 micrograms) caused tracheal relaxation, which was abolished by cutting hindlimb nerves. We conclude that both pulmonary and bronchial C-fibers evoke tracheal contraction, but when capsaicin is injected into the left atrium any effects of stimulating bronchial C-fibers are masked by the reflex action of somatic afferents, which cause tracheal relaxation.

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Microsphere estimates of blood flow: methodological considerations

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.254.2.g275 ◽

1988 ◽

Vol 254 (2) ◽

pp. G275-G279

Author(s):

C. von Ritter ◽

R. A. Hinder ◽

W. Womack ◽

P. Bauerfeind ◽

C. J. Fimmel ◽

...

Keyword(s):

Blood Flow ◽

Reference Sample ◽

Mucosal Blood Flow ◽

Gastric Mucosal Blood Flow ◽

Volume Loss ◽

Dextran 70 ◽

Anesthetized Dogs ◽

Methodological Considerations ◽

Pentobarbital Sodium Anesthesia ◽

Reference Samples

The microsphere technique is a standard method for measuring blood flow in experimental animals. Sporadic reports have appeared outlining the limitations of this method. In this study we have systematically assessed the effect of blood withdrawals for reference sampling, microsphere numbers, and anesthesia on blood flow estimates using radioactive microspheres in dogs. Experiments were performed on 18 conscious and 12 anesthetized dogs. Four blood flow estimates were performed over 120 min using 1 X 10(6) microspheres (15 microns) each time. The effects of excessive numbers of microspheres (13 million), pentobarbital sodium anesthesia (30 mg/kg), and replacement of volume loss for reference samples with dextran 70 were assessed. In both conscious and anesthetized dogs a progressive decrease in gastric mucosal blood flow and cardiac output was observed over 120 min. This was also observed in the pancreas in conscious dogs. The major factor responsible for these changes was the volume loss due to reference sample withdrawals. Replacement of the withdrawn blood with dextran 70 led to stable blood flows to all organs. The injection of excessive numbers of microspheres did not modify hemodynamics to a greater extent than did the injection of 4 million microspheres. Anesthesia exerted no influence on blood flow other than raising coronary flow. We conclude that although blood flow to the gastric mucosa and the pancreas is sensitive to the minor hemodynamic changes associated with the microsphere technique, replacement of volume loss for reference samples ensures stable blood flow to all organs over a 120-min period.

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Reflex tracheal gland secretion evoked by stimulation of bronchial C-fibers in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1982.53.4.985 ◽

1982 ◽

Vol 53 (4) ◽

pp. 985-991 ◽

Cited By ~ 72

Author(s):

B. Davis ◽

A. M. Roberts ◽

H. M. Coleridge ◽

J. C. Coleridge

Keyword(s):

Bronchial Artery ◽

Gland Secretion ◽

Vagus Nerves ◽

Television Camera ◽

C Fibers ◽

Submucosal Glands ◽

Before And After ◽

Lower Trachea ◽

Anesthetized Dogs ◽

Trachealis Muscle

We examined the effect of stimulating bronchial C-fibers on tracheal submucosal gland secretion in anesthetized dogs with open chest and lungs ventilated through the lower trachea. We opened the upper trachea in the midline, retracted the cut edges, and sprayed powdered tantalum onto the exposed mucosa. Secretions from the ducts of submucosal glands caused elevations (hillocks) in the tantalum layer, which were viewed through a microscope and recorded on videotape with a television camera. We counted the hillocks (greater than 0.2 mm diam) in an area of mucosa (1.2 cm2) before and after injecting capsaicin (3 micrograms) into a bronchial artery to stimulate bronchial C-fibers. In the minute before capsaicin was injected 7 +/- 2 (mean +/- SE; n = 20) hillocks appeared and in the minute after 40 +/- 2 hillocks. Bradykinin (1.5 micrograms) had similar effects. Secretion was accompanied by contraction of the trachealis muscle. Effects were abolished by cooling (0 degree C) or cutting the vagus nerves. Since capsaicin and bradykinin stimulate bronchial C-fibers selectively when injected in these small doses, we conclude that bronchial C-fibers furnish the afferent arm of an airway secretory reflex.

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