Anthony W. Quail

Selective manipulation of neurohumoral control of the cardiac pacemaker by drugs given intrapericardially.

A technique of intrapericardial administration of beta-adrenoceptor and muscarinic cholinergic receptor antagonist drugs has been tested in conscious rabbits. Intrapericardial propranolol or atenolol (50 micrograms/kg) had the same effect on isoprenaline heart rate dose-response curves and on the sympathetic component of the arterial baroreceptor-heart rate reflex as did conventional, 5-fold greater, intravenous doses of the drugs. The action of intrapericardial propranolol was attributable to its (-)isomer. Intrapericardial propranolol (50 micrograms/kg) had little effect on ventricular contractility. Plasma levels of propranolol and atenolol after intrapericardial administration were, respectively, 7- and 40-fold less than after the usual intravenous doses. Intrapericardial hyoscine methyl bromide (10 micrograms/kg) abolished baroreflex vagal effects on heart rate as effectively as did the conventional, 5-fold greater, intravenous dose. The duration of receptor blockade by both classes of drugs when given intrapericardially was at least 2 hr. We conclude that the rapid diffusion of beta-adrenoceptor and muscarinic cholinergic receptor blocking drugs from the pericardial sac to receptors on the sinoatrial cardiac pacemaker, and their prolonged actions, provides a useful technique for preventing the actions of the sympathetic and vagus nerves, and of circulating catecholamines, on the chronotropic functions of the heart.

Heart–Lung Interactions: The Sigh And Autonomic Control In The Bronchial And Coronary Circulations

1. The Darwin hypothesis that human and animal expressions of emotion are the product of evolution and are tied to patterns of autonomic activity specified to progress the emotion remains under challenge.

Central nervous system 5-hydroxytryptamine and noradrenaline specificity of ear vascular and ventilation reflexes in thermoregulating rabbits

Contrasting hypotheses of mammalian thermoregulation were tested in unanesthetized rabbits in relation to the role of the central nervous (CNS) monoamines 5-hydroxytryptamine (5-HT) and noradrenaline (NA) in regulating lung function and ear skin blood flow (Doppler flowmeter). Normal rabbits and rabbits with CNS depletion of 5-HT and NA (caused by the neurotoxins 5,7-dihydroxytryptamine and 6-hydroxydopamine) were studied in an airconditioned chamber at ambient temperatures of 12 degrees, 22 degrees and 35 degrees C. The results suggest that CNS 5-HT plays an excitatory role in the heat conservation mechanism of cold-induced ear skin vasoconstriction, and that this effect is inhibited by CNS NA to cause heat dissipation during heat stress. Both CNS 5-HT and NA appear to exert a mild inhibitory restraint on ventilation even during heat stress. The data support the theory that CNS 5-HT is concerned with heat conservation and CNS NA with heat loss mechanisms in the cutaneous circulation, and that both monoamines moderate heat loss through panting. CNS monoamine-dependent thermoregulation in the rabbit thus resembles the model postulated for the cat, dog and monkey rather than, as previously proposed, for the sheep and goat.

EFFECTS OF CHANGING HAEMATOCRIT, VENTRICULAR RATE AND MYOCARDIAL INOTROPY ON THE ACCURACY OF IMPEDANCE CARDIOGRAPHY

1. The accuracy and limitations of the non‐invasive impedance cardiograph technique were examined in dogs with electromagnetic flow‐transducers mounted on the aortic root over a wide range of physiological conditions of anaemia, heart rate, stroke volume and myocardial inotropy.

Effect of fentanyl on baroreflex control of circumflex coronary conductance

1. Fentanyl, a synthetic μ‐opioid receptor agonist, is the preferred induction and maintenance anaesthetic agent in cardiac surgery.

Neural control of the bronchial circulation

A distinction may be drawn between studies that define potential mechanisms of control, those that define components of control systems, and those that determine the priority of controls in the integrated system. It is the priority controls that determine survival in the environment. These different kinds of studies are necessary and complementary. In the case of the bronchial circulation, we continue with an era of defining potential mechanisms and component systems. These have been excellently reviewed by Godden (1990) and by Coleridge & Coleridge (1994). However, we have a long way to go before we establish priority neural controls in the integrated system. Cogent examples in the bronchial circulation might be the interaction at rest between neural controls and tonic NO released from vascular endothelium in determining basal autonomic tone. Another might be the autonomic controllers of bronchial resistance vessels reflexly evoked at the onset of exercise, and how these controls are modified by central temperature regulation as exercise continues. These kinds of data are necessary to understand evolutionary mechanisms that protect the organism from untoward environmental influence, and that point to support therapies for systems breakdown.

Recent Views On Integrated Coronary Control: Significance Of Non‐Uniform Regional Control Of Coronary Flow Conductance

1. Previous work from this laboratory and others has shown that powerful autonomic influences modulate coronary flow. In particular, the parasympathetic nervous system produces vasodilatation when activated by baroreceptors via the vagus nerve.

BAROREFLEX CONTROL OF CORONARY BLOOD FLOW VARIES REGIONALLY IN AWAKE DOGS

1. Baroreflex responses to changes in aortic pressure were measured simulataneously in three main coronary regions of awake dogs.

Influence of the timing of internal fixation of femur fractures during shock resuscitation on remote organ damage

Reamed intramedullary nailing is the gold standard for management of femur fractures. Nailing within 24 h is proven to reduce complications from ongoing bleeding, soft‐tissue damage and pain. However, when combined with haemorrhagic shock, femur fracture and intramedullary nailing are associated with immune‐mediated damage to remote organs. We studied whether delaying fracture fixation until resuscitation was succeeding would lead to a significant reduction in remote organ damage.

Analysis of bronchovascular downstream blood pressure changes in exercising sheep.

The relative roles of neural and pressure gradient factors, causing a fall or maintenance of bronchial blood flow in exercising sheep, are unknown. These were examined in sheep prepared under thiopentone/isoflurane general anaesthesia with a pulsed Doppler probe mounted on the bronchial artery, and aortic pressure (Pa) catheter in superficial cervical artery. After recovery, Swan-Ganz catheters were inserted under local anaesthesia into the pulmonary artery. Bronchial flow and conductance (Qbr, Cbr), and pressure gradients (Pg; i.e. aortic minus right atrial, Pg_RAP; pulmonary artery, Pg_Ppa; and, left atrial (wedge) Pg_LAP) were derived from continuous records, after switching between downstream sites during and after moderately severe treadmill exercise (3.8 km.h−1, for 1.7 min, 6 min recovery). The protocol was repeated after combined α1,α2–adrenoceptor/cholinoceptor blockade using phentolamine methanesulfonate and methscopolamine bromide. Bronchial flow fell in both receptor intact (INT) and (BL) blocked state. Pa rose in INT, but downstream pressures rose only 3.7 (RAP), 2.8 (Ppa) and 2.0 (LAP) mmHg (P for each <0.05) in both INT and BL. Pg_RAP and Pg_Ppa did not rise, but Pg_LAP rose 4.0 mmHg (P < 0.05). In BL, Pa fell, as did Pg_RAP (7.0 mmHg, P < 0.05), Pg_Ppa (8.9 mmHg, P < 0.001), but Pg_LAP did not change. Thus, downstream pressures change by small amounts, and pressure gradients to RAP and Ppa sites do not change during moderately severe exercise in normal sheep. The fall in Qbr in INT is due to neural factors, but in BL is due to a fall in Pg. The relative rise in Pg_LAP in both INT and BL favours redistribution within total Qbr to the pulmonary capillary/vein/left atrium site.