Key result
In anaesthetized rabbits, aortic baroreceptors and vagal afferent input are not needed for the iANF response to blood volume changes, whereas intact aortic baroreceptors are essential for iVP changes.
In anaesthetized rabbits, the iANF response to blood volume changes does not require aortic baroreceptor or vagal afferent input, unlike iVP which requires intact aortic baroreceptors.
Animal data preclude practice change; leaves open baroreceptor roles in human ANF/VP volume responses.
The influence of aortic baroreceptors and vagal afferent nerves on the release of immunoreactive vasopressin (iVP) and immunoreactive atrial natriuretic factor (iANF) was examined in anaesthetized rabbits. Changes in plasma concentrations of iVP and iANF, heart rate, mean arterial pressure, and right atrial pressure were measured in response to blood volume changes (+20, +10, -10, -20%). Carotid sinus pressure was maintained at 100 mmHg (1 mmHg = 133.3 Pa), and blood volume changes were performed before and after bilateral vagotomy (VNX) in all experiments. Two experimental groups were studied: rabbits with aortic depressor nerves intact (ADNI) and those with aortic depressor nerves sectioned (ADNX). Mean arterial and right atrial pressures decreased during haemorrhage and increased in response to volume expansion. Plasma iVP concentrations increased with haemorrhage and decreased with volume expansion in the ADNI group. Plasma iANF, however, decreased with haemorrhage and increased during volume expansion in both ADNI and ADNX groups. Vagotomy caused an increase in baseline plasma iANF in the ADNX group. The responses of iANF to blood volume changes were augmented after VNX and ADNX. The results show that neither the aortic baroreceptor nor the vagal afferent input are needed for the iANF response to changes in blood volume, over the range of +/- 20%. In contrast, intact aortic baroreceptors are essential for changes in circulating iVP in this preparation.
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Courneya et al. (1989) studied Blood volume changes. Blood volume changes and bilateral vagotomy vs. Baseline / intact nerves was evaluated on Plasma concentrations of iVP and iANF. In anaesthetized rabbits, aortic baroreceptors and vagal afferent input are not needed for the iANF response to blood volume changes, whereas intact aortic baroreceptors are essential for iVP changes.
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