Gender Differences in Sympathetic Nervous System Regulation

Abstract

1. Females are protected against the development of hypertension. The purpose of the current review is to present the evidence for gender differences in the regulation of the sympatho-adrenal nervous system and to determine if these differences support the hypothesis that, in females, the regulation of the sympathetic nervous system (SNS) is altered such that sympatho-adrenal activation is attenuated or sympatho-adrenal inhibition is augmented. 2. The central control of sympatho-adrenal function is different in females and responses vary during the oestral and menstrual cycles. Pathways regulating the SNS appear to be less sensitive to excitatory stimuli and more sensitive to inhibitory stimuli in females compared with males. 3. Gender differences in arterial baroreflex sensitivity suggest that females may have a greater baroreflex sensitivity, such that alterations in blood pressure are more efficiently controlled than in males. Cardiopulmonary reflex inhibition of sympathetic nerve activity is greater in females, possibly resulting in a greater renal excretory function. 4. An attenuated sensitivity to adrenergic nerve stimulation, but not to noradrenaline (NA), suggests that gender differences in noradrenergic neurotransmission may protect females against sympathetic hyperactivity. Gender differences in the regulation of NA release via presynaptic alpha 2-adrenoceptors, the vasoconstrictor response to the cotransmitter neuropeptide Y and the clearance of catecholamines are consistent with this hypothesis. 5. Similarly, attenuated stress-induced increases in plasma catecholamines in women suggest that females are less sensitive and/or less responsive to adrenal medullary activation. This is supported by findings of gender differences in adrenal medullary catecholamine content, release and degradation. 6. We conclude that there is strong evidence that supports the hypothesis that, in females, the regulation of the SNS is altered such that sympatho-adrenal activation is attenuated or sympatho-adrenal inhibition is augmented.

Clinical Signicance of Blood Pressure Response Triggered by a Doctor's Visit in Patients with Essential Hypertension.

“…In fact, there is growing evidence that sex affects the regulation of the sympathetic nervous system. It has been shown that pathways regulating the sympathetic nervous system appear to be more sensitive to excitatory stimuli and less sensitive to inhibitory stimuli in men than in women (12). This means that a similar level of external stimuli would more easily and/or more markedly induce excitation of the sympathetic nervous system in men than in women, and would seem to offer a good explanation of the present results.…”

The effect of gender on the sympathetic nerve hyperactivity of essential hypertension

“…48 In that report, the baroreceptor reflex sensitivity controlling MSNA was found to be increased in relation to increased plasma levels of oestrogen and progesterone. 48 Although we did not examine the mechanisms underlying the observed gender-related differences, taking the above considerations together with previously published reports, 20,41,49,50 it is reasonable to raise the possibility that the lower sympathetic activity in women could be related to their greater sympatho-inhibitory baroreceptor reflexes than those in men. This normal genderrelated difference would then affect the level of the central sympathetic hyperactivity attained in women and men with hypertension.…”

Sympathetic nerve hyperactivity of essential hypertension is lower in postmenopausal women than men

“…Apart from the severity of hypertension and lipid disorders, other possible factors related to cardiovascular risk in postmenopausal women have included vascular responsiveness to neural and neurotransmitter effects, as well as the levels of various hormonal systems. 2,5,28,31 Such considerations assume relevance when considering the choice of hypertension management and antihypertensive therapy.…”