https://nova.newcastle.edu.au/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1392 Sat 24 Mar 2018 08:27:59 AEDT ]]> https://nova.newcastle.edu.au/vital/access/manager/Repository/uon:12114 br) and dimensions during moderate and strenuous exercise, and to analyse the role of vagal and sympathetic nerves. Methods: Nine ewes (34–44 kg) underwent left thoracotomy during general anaesthesia (thiopentone/isoflurane) and either (5 sheep = Group 1) a pulsed Doppler transducer was placed on the bronchial artery, or (4 sheep = Group 2) a pulsed Doppler transducer was placed on the bronchial artery, and transit-time and single crystal sonomicrometers were mounted on the left main bronchus. These measured continuously Q_br, bronchial circumference (Circ_br) and wall thickness (Th_br). Aortic pressure (P_a) and central venous pressure catheters were placed in the superficial cervical artery and vein. Trained sheep exercised on a horizontal treadmill, i.e. Group 1, moderate exercise 2.2 mph over 1.6, 6 min recovery, for analysis of changes in Q_br before and after cholinoceptor blockade; Group 2, strenuous exercise 4.4 mph over 2, 10 min recovery for analysis of changes in Q_br and airway dimensions, before and after cholinoceptor plus α₁-, α₂-adrenoceptor blockade. β-adrenoceptor systems were intact. Results: In Group 1 during moderate exercise P_a and heart rate (HR) rose. Q_br and blood flow conductance (C_br) fell immediately to 83% (P<0.001) before returning toward resting levels, but fell when exercise ceased to 89% (P<0.01) before recovering. Prior cholinoceptor blockade abolished the immediate fall in Q_br and C_br, but not the recovery vasoconstriction. Later in recovery the bronchial bed dilated progressively over 6 min (P<0.05). In Group 2 during strenuous exercise P_a and HR rose substantially. Q_br and C_br fell to 68% and 54% (P<0.001), respectively, and there was early vasoconstriction in recovery. Circ_br fell immediately and remained at 93% (P<0.01), and did not recover fully when exercise ceased. Th_br did not change during or after exercise. Prior cholinoceptor plus α-adrenoceptor block caused P_a and Q_br to fall slightly during exercise, but the bronchovascular constriction during and after exercise was abolished, as was circumferential shortening in the airway. Conclusions: At exercise onset and steady-state, resetting the arterial baroreflex upward in sheep increases parasympathetic cholinergic vasoconstrictor activity and causes bronchial wall and bronchovascular smooth muscle contraction in concert with sympathetic adrenergic constriction of systemic vascular beds. Whether the known sigmoid baroreflex control of tracheal smooth muscle tension at rest is extended to tracheobronchial smooth muscle and its circulation during exercise is yet to be determined.]]> Sat 24 Mar 2018 08:13:00 AEDT ]]> https://nova.newcastle.edu.au/vital/access/manager/Repository/uon:12192 br) and conductance (C_br), bronchial circumference (Circ_br) and wall thickness (Th_br). In Protocol 1 (P1), four sheep ran duplicate 5 min protocols on a horizontal treadmill at continuous step-up-and-down speeds of 1 min duration, namely, 0.8, 1.6, 2.2, 1.6 and 0.8 mph (moderate exercise), followed by 10 min recovery. In P2, four sheep ran duplicate 2 min protocols at constant 4 mph (strenuous exercise), and in P3, one sheep ran duplicate protocols each of 3 min at 2.2, 4.4 and 6 mph (severe exercise). Regression analysis and repeated measures ANOVA were used to assess differences between times, runs and exercise intensity. In P1, airway effects were directly related to graded exercise effort sustained over 5 min. Peak effects occurred at 2.2 mph, except for Th_br. Heart rate and Pa rose (to 156% and 111% of resting, respectively), and Q_br and C_br fell (to 83% and 75%; both P<0.001). Circ_br fell to 96% (P=0.02), and Th_br rose at low speeds early and late, and thinned at the highest speed. In P2 and P3 for all variables the steady-state effects were systematically greater than for P1 (4.4 mph: Cbr to 43%, Circ_br to 93%; 6.6 mph: C_br to 25%, Circ_br to 82%). There was no significant recovery hyperaemia, but there was residual post-exercise bronchoconstriction. The exercise stimulus–response relationships from rest to a maximal 6 mph for sheep airway circumference and its bronchial circulation are inverse and functionally constrictor.]]> Sat 24 Mar 2018 08:08:28 AEDT ]]>