Adrenergic and Vagal Influences on Blood Pressure Variability

Abstract

The present paper reviews our recent studies set up to define the role of sympathetic and vagal nervous influences on blood pressure variability. Blood pressure and its variability was measured in men by Arteriosonde or by Portometer (the latter recording 12 hours ambulatory blood pressure) and in the dog by intraarterial recordings. It was shown that sympathetic nerves do not influence variability as no change was seen with drugs acting on either beta (atenolol, metoprolol, propranolol) or alpha adrenergic receptors (prazosin, phentolamine, guanfacine). Also no correlation was found with plasma catecholamines or sympathetic function tests. By contrast, clear inhibition was demonstrated with atropine indicating an important role of vagal nerves on variability. However, in men, inhibition was not complete with atropine; thus, also other mechanisms play a role but these are, at present, largely unknown.

Longitudinal studies on the effect of hypertension on circadian hemodynamic and autonomic rhythms in telemetered rats

“…It is noteworthy that the complications of hypertension including end-organ damage relate not only to the increase in the average BP levels but also to abnormalities in the upward and downward BP fluctuations around the average levels (Mancia and Parati, 2000). The increased BP oscillations during hypertension has been attributed to the apparent instability in the vessels of hypertensive rats (Clement et al, 1985;Friberg et al, 1989), which may cause fluctuations in the developed force and possibly amplify pressor and depressor responses to changes in peripheral autonomic control. The increased long-term hemodynamic variability in SHRs may also be accounted for by the elevated sympathetic tone (Murphy et al, 1991;El-Mas and AbdelRahman, 2000), which is known to contribute to the enhanced BP and HR oscillation in hypertension (Takalo et al, 1994).…”

Respiration‐synchronous fluctuations in stroke volume, heart rate and arterial pressure in humans.

“…In another study, no change in MAP variability was seen in cat or man after atropine administration (Mancia et al 1985). In a study of long-term variability in HR and blood pressure, atropine caused a decrease in the variability of diastolic arterial pressure, but no significant change was observed in the variability of systolic arterial pressure 'indicating that the SV variations were still present after cholinergic blockade' (Clement, De Pue, Jordaens & Packet, 1985).…”

Short‐term cardiovascular oscillations in man: measuring and modelling the physiologies

“…Whether either or both are active in respiratory sympathetic fluctuations, the reflex pattern should reduce arterial pressure oscillations with breathing. However, published data on blockade of sympathetic effects via α‐adrenergic antagonism provide no clear insight; only overall variance (Clement et al 1985) or ‘relative contribution’ (Nakata et al 1998) or ‘normalized’ changes (van de Borne et al 2001) have been presented. Thus, no published data present the possible blood pressure buffering role for respiratory‐related vascular sympathetic oscillations.…”