The effects of distension of the small intestine on myocardial blood flow in anaesthetised cats: possible relevance to coronary vasospasm

Moore, G. E.; Parratt, J. R.

doi:10.1007/bf01910407

Cited by 3 publications

(1 citation statement)

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“…Distension of the upper part of the small intestine has been reported to cause a transient increase in arterial blood pressure and a decrease in myocardial blood flow; the latter was assessed by a heat clearance method using a thermocouple inserted into the myocardium (Moore & Parratt, 1977). However, the reflex mechanism for these changes was not examined.…”

Section: Abdoii1 Inal Visceramentioning

confidence: 99%

Reflex effects on the coronary circulation

Mary

1992

Experimental Physiology

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Section: Abdoii1 Inal Visceramentioning

confidence: 99%

Reflex effects on the coronary circulation

Mary

1992

Experimental Physiology

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The evidence for α-adrenoceptors in the coronary circulation and their possible relevance to the physiological regulation of myocardial blood flow

Parratt

1981

Basic Res Cardiol

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This contribution reviews the evidence for the existence of a-adrenoceptors mediating vasoconstriction in the coronary vascular bed and discusses their possible physiological, pharmacological and clinical relevance. It attempts to serve as an introduction to the papers in this symposium which deal with the role of the sympathetic nerves in the control of coronary vessel tone. Evidence for the presence of coronary vascular a-adrenoceptors mediating vasoconstrictionThe experimental evidence for the presence of coronary vascular a-adrenoceptors comes both from in-vitro and in-yivo studies: I. a-adrenoceptors in the coronary circulation: evidence from isolated coronary vesselsOne of the problems involved in analysing adrenoceptor types in the coronary circulation' is that most of the commonly used agonists (e.g. adrenaline, noradrenaline) influence both coronary and myocardial a-and [~-adrenoceptors. A drug may have a direct constrictor effect on the coronary vessels (mediated, for example, through coronary vascular smooth muscle a-adrenoceptors) yet increase coronary flow through stimulation of myocardial work and metabolism (mediated, for example, through myocardial [3-adrenoceptors). This separation of direct (vascular) from indirect (myocardial) effects is especially difficult with regard to drugs which influence adrenoceptors. One obvious way of separating metabolically mediated from direct coronary vascular effects is to examine the responses of isolated coronary vessels. It must however, be emphasised that such studies do not yield definitive information about the responses of such vessels in vivo nor about the responses of the coronary arterioles, the main resistance segment of the coronary vascular bed. The classic studies in this field are those of Bohr (1, 2) who examined the responses of canine coronary arteries of different sizes ('small', 250-500 ~ and 'large' 1.5-2.4 mm diameter) to adrenoceptor agonists. A more detailed study of the responses of pig coronary arteries (spiral strips from arteries 1.5-2.4 mm diameter) has been undertaken by Abaitey (3). The predomin-978

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Coronary vascular response to the cerebral ischemia reflex.

Boel

Gutterman

1993

Hypertension

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Most centrally mediated sympathoexcitatory reflexes produce increases in arterial pressure, heart rate, and peripheral vascular resistance, including coronary vasoconstriction. Cerebral ischemia also causes large increases in arterial pressure and peripheral vasoconstriction but with modest or variable changes in heart rate. To examine the effect of cerebral ischemia on coronary vascular resistance, we produced cerebral ischemia in 14 cats by occluding the right brachiocephalic and left subclavian arteries for 30 seconds. After vagotomy and ^-blockade, a marked increase in arterial pressure (89±14%) and coronary vascular resistance (52 ±7%) was seen. After inhibition of the carotid baroreceptor reflex by surgical denervation and application of topical lidocaine, the increase in arterial pressure to cerebral ischemia was not affected, but the increase in coronary vascular resistance was attenuated (33 ±6%; p<0.05 versus before denervation) to a level expected with autoregulation. To evaluate the possible contribution of the chemoreflex on coronary blood flow during cerebral ischemia, we conducted separate experiments in which nicotine was injected into both carotid arteries. Coronary constriction was not observed. Adrenalectomy and upper extremity ischemia likewise did not alter coronary vascular resistance. We conclude that cerebral ischemia elicits neurally mediated coronary vasoconstriction as a result of baroreceptor hypotension rather than directly. The relative absence of neurogenic coronary constriction and changes in heart rate suggest that sympathoexcitation during cerebral ischemia is directed more toward the peripheral vasculature than the heart. {Hypertension 1993;21:216-221) KEY WORDS • vasoconstriction • pressoreceptors • sympathetic nervous system • cerebral ischemiaA variety of reflex stimuli produce a-adrenergicmediated coronary vasoconstriction. Barore->. ceptor hypotension, 1 activation of carotid chemoreceptors, 2 and nociceptive reflexes, 3 as well as static 4 and dynamic exercise, 5 all increase systemic arterial pressure, heart rate, and coronary vascular resistance through sympathetic activation.Cerebral ischemia, produced by interruption of perfusion to the head, is a potent stimulus for sympathetic discharge. However, unlike most sympathoexcitatory reflexes, tachycardia is not a consistent feature of the ischemic response. The effect of cerebral ischemia on coronary flow is difficult to predict. The large pressor response to cerebral ischemia suggests that neurogenic coronary constriction accompanies the sympathoexcitation. However, other sympathoexcitatory reflexes producing coronary constriction include tachycardia. BradyFrom the Veterans Administration

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The effects of distension of the small intestine on myocardial blood flow in anaesthetised cats: possible relevance to coronary vasospasm

Cited by 3 publications

References 35 publications

Reflex effects on the coronary circulation

Reflex effects on the coronary circulation

The evidence for α-adrenoceptors in the coronary circulation and their possible relevance to the physiological regulation of myocardial blood flow

Coronary vascular response to the cerebral ischemia reflex.

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