TY - JOUR

T1 - Afferent discharges from coronary arterial and ventricular receptors in anaesthetized dogs

AU - Drinkhill, M J

AU - Moore, J

AU - Hainsworth, R

PY - 1993/12/1

Y1 - 1993/12/1

N2 - Previous work has shown that increases in aortic root pressure result in reflex vasodilation, and that this response is likely to result mainly from stimulation of receptors in the coronary arteries, although contribution from left ventricular receptors was not excluded. This investigation was undertaken to resolve this question and to determine the afferent nerve fibres likely to be involved in this reflex. 2. In chloralose-anaesthetized dogs a perfusion circuit was used which allowed us to change the pressures in: (a) the aortic root, coronary arteries and the left ventricle; (b) aortic root and coronary arteries at constant ventricular pressure; and (c) the left ventricle with mean (although not pulse) aortic pressure constant. Electrophysiological recordings were made from slips dissected from the vagus nerve which responded with an increase in discharge to either combined increases in the pressures, or to aortic root injections of veratridine. 3. Recordings were made from twenty-one vagal afferents. On the basis of their conduction velocities, eleven were classified as non-myelinated and ten as myelinated. 4. Three non-myelinated afferents responded to veratridine injections only, three to both veratridine and combined aortic root and ventricular pressure changes, and five to pressure changes only. Responses to pressure occurred only when ventricular systolic pressure exceeded 30 kPa. 5. None of the myelinated afferents responded to veratridine. All showed increases in discharge to combined increases in mean aortic root, coronary arterial and left ventricular systolic pressures, which would be graded over a range similar to that which caused reflex changes. All were more sensitive to changes in mean coronary pressure than to changes in ventricular systolic pressure. 6. We conclude that myelinated vagal afferent nerve fibres, which respond predominantly to changes in mean coronary arterial pressure, are likely to be responsible for the vasodilation to the changes in mean aortic root pressure previously reported. These fibres are probably attached to coronary arterial mechanoreceptors.

AB - Previous work has shown that increases in aortic root pressure result in reflex vasodilation, and that this response is likely to result mainly from stimulation of receptors in the coronary arteries, although contribution from left ventricular receptors was not excluded. This investigation was undertaken to resolve this question and to determine the afferent nerve fibres likely to be involved in this reflex. 2. In chloralose-anaesthetized dogs a perfusion circuit was used which allowed us to change the pressures in: (a) the aortic root, coronary arteries and the left ventricle; (b) aortic root and coronary arteries at constant ventricular pressure; and (c) the left ventricle with mean (although not pulse) aortic pressure constant. Electrophysiological recordings were made from slips dissected from the vagus nerve which responded with an increase in discharge to either combined increases in the pressures, or to aortic root injections of veratridine. 3. Recordings were made from twenty-one vagal afferents. On the basis of their conduction velocities, eleven were classified as non-myelinated and ten as myelinated. 4. Three non-myelinated afferents responded to veratridine injections only, three to both veratridine and combined aortic root and ventricular pressure changes, and five to pressure changes only. Responses to pressure occurred only when ventricular systolic pressure exceeded 30 kPa. 5. None of the myelinated afferents responded to veratridine. All showed increases in discharge to combined increases in mean aortic root, coronary arterial and left ventricular systolic pressures, which would be graded over a range similar to that which caused reflex changes. All were more sensitive to changes in mean coronary pressure than to changes in ventricular systolic pressure. 6. We conclude that myelinated vagal afferent nerve fibres, which respond predominantly to changes in mean coronary arterial pressure, are likely to be responsible for the vasodilation to the changes in mean aortic root pressure previously reported. These fibres are probably attached to coronary arterial mechanoreceptors.

KW - Afferent Pathways

KW - Anesthesia

KW - Animals

KW - Blood Pressure

KW - Coronary Vessels

KW - Dogs

KW - Electrophysiology

KW - Female

KW - Heart

KW - Heart Ventricles

KW - Male

KW - Reflex

KW - Vagus Nerve

KW - Ventricular Function

KW - Ventricular Function, Left

KW - Veratridine

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1113/jphysiol.1993.sp019973

DO - 10.1113/jphysiol.1993.sp019973

M3 - Article

C2 - 8145172

VL - 472

SP - 785

EP - 799

JO - Journal of Physiology

JF - Journal of Physiology

SN - 0022-3751

IS - 1

ER -