Control of blood pressure by carotid sinus baroreceptors in human beings

Most techniques available for studying arterial baroreflexes in man are unsuitable for analysis of the primary function of these reflexes, that is, arterial pressure control. Such control can be evaluated during increases and decreases in carotid baroreceptor activity obtained with a variable pressure neck chamber. This study reviews some technical aspects of the technique and describes the influence the carotid baroreceptors exert on arterial pressure in normotensive subjects and in those with essential hypertension. Major differences can be found in the two populations. In normotensive subjects the change in blood pressure is greater with a decrease than with an increase in baroreceptor activity. The former response becomes progressively less and the latter progressively greater with increasingly high blood pressure, so that in severe hypertension the reflex shows an asymmetry opposite to that in normotensive subjects, the change in blood pressure being greater with an increase than with a decrease in baroreceptor activity. These results imply that in human hypertension the carotid baroreflex mechanism controlling blood pressure undergoes a very marked resetting but shows no major reduction in sensitivity. In hypertensive subjects cardiac output and peripheral resistance were also measured. It was found that the depressor response to an increase in carotid baroreceptor activity depends on both a reduction in cardiac output and a systemic vasodilatation. However, peripheral vasoconstriction is the only factor accounting for the pressor response to reduced baroreceptor activity. © 1979.