Gender, sex hormones and autonomic nervous control of the cardiovascular system

Differences in the autonomic system may be due to differences in afferent receptor stimulation, in central The autonomic nervous system is of importance in the reflex transmission, in the efferent nervous system and in natural history and treatment of a number of post synaptic signaling. At each of these potential sites of pathophysiological states involving the cardiovascular difference, there may be effects due to different size or system. These include hypertension and diseases of the number of neurons, variations in receptors, differences in vasculature as well as myocardial ischaemia and cardiac neurotransmitter content or metabolism as well as func- arrhythmias. Gender differences in the incidence and tional differences in the various components of the reflex clinical course of a range of cardiovascular states are also arc. well recognised. Both short and long term prognosis after myocardial infarction are worse for women than men (1-4), whereas women with non-ischaemic car- 2. Methods of assessment of autonomic nervous diomyopathy have improved survival (5,6). In addition to activity the well known difference in age of presentation of coronary heart disease, women are more likely to suffer As indicated in the Introduction there are multiple from Raynaud's phenomenon, and to experience pre- potential sites in the autonomic nervous system which may syncopal or syncopal episodes. An appreciation of gender be subject to gender related differences. Consequently the differences in the structure and function of the autonomic examination of gender differences may require use of a nervous system is therefore important to a full understand- wide range of experimental and clinical methodologies. In ing of a number of common and important clinical this section brief mention will be made of techniques presentations (7). specifically related to this question. Gender differences in the autonomic nervous system Neurotransmitter release from efferent terminals may be may be present because of developmental differences or estimated from plasma levels, particularly for the sympa- due to the effects of prevailing levels of male and / or thetic nervous system by measuring plasma noradrenaline female sex hormones. Such prevailing hormone levels may (NA) and adrenaline levels or their urinary excretion. Such also produce differences between pre- and post-menopaus- methods, which are available for both animal and human al women and amongst pre-menopausal women at different studies, do not account for clearance or regional changes phases of the menstrual cycle, which is characterized by that may however be estimated from determination of oestrogen secretion in the late follicular (pre-ovulatory) transmitter spillover (8). It is also possible to measure phase followed by a secondary phase of secretion in the extracellular concentrations regionally from microdialysis. luteal (post-ovulatory) phase. Progesterone secretion oc- Estimation of cholinergic neurotransmission by assay of curs during the luteal phase.