Investigation into the Vasomotor Signs and Symptoms of the Menopause

Abstract

The mechanism of the menopausal hot flush was investigated. Physiological changes, as well as changes in plasma and whole blood pharmacological activity were examined in post-menopausal women, at rest and during a hot flush, and in a group of pre-menopausal controls, at rest and during heat induced vasodilatation. The hot flush was found to be associated with an altered cardiovascular activity and an increase in skin surface temperatures. There was a difference in the contractile activity of plasma from post-menopausal women, at rest and during a hot flush, upon the methysergide blocked rat fundic strip. This suggested the involvement of a humoral component in the mechanism of the hot flush. This humoral component did not appear to be simply due to vasodilatation since there was no difference in the contractile activity of plasma from premenopausal women at rest and during heat induced vasodilatation. 17B-oestradiol appeared to affect the responsiveness of both vascular and non-vascular sympathetically innervated smooth muscle. 178- oestradiol depressed the responses of the rat isolated vas deferens to transmural stimulation to noradrenaline and to potassium chloride. This suggested a direct action of 178-oestradiol upon the smooth muscle. Furthermore, 17B-oestradiol, given in a dose which is considered physiological, increased the pressor responses of the female pithed rat to stimulation of the spinal sympathetic outflow but left responses to noradrenaline and angiotensin more or less unaffected. In addition 178-oestradiol given at a higher amount decreased the pressor responses of the female pithed rat to stimulation of the spinal sympathetic outflow. The pressor responses to noradrenaline and angiotensin were again left more or less unaffected. These results suggested a biphasic action of 178-oestradiol on the presynaptic site, at the neuroeffector junction of the vascular smooth muscle. Although the mechanism of the menopausal hot flush has not been completely elucidated, it appears to involve both a humoral and a nervous component. Furthermore, the hot flush may be related to the hormonal changes occurring at the menopause, since 178-oestradiol was found to affect the vascular smooth muscle.