Alpha-2 adrenergic activity in perimenopausal women.

Lipid alterations and increased blood pressure may occur during perimenopause. No data are available in perimenopausal women on the alpha-2 adrenergic activity which affects norepinephrine secretion. We studied cardiovascular and catecholamine responses to clonidine (300 mg per os) in a group of 15 perimenopausal women (PeriMW) and in a control group of 13 premenopausal women (PreMW). Nine of the perimenopausal women were also studied after 4-month percutaneous estrogen replacement therapy (PeriMWE). Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), plasma norepinephrine (NE) and epinephrine (E) were evaluated before and at 120 min, 130 min, 140 min after clonidine administration. Basal values of SBP, DBP and HR were not different (F = 0.7, p = NS; F = 0.2, p = NS and F = 0.1, p = NS respectively) between PeriMW both before and after therapy and PreMW. Resting levels of E were similar in PreMW and in PeriMW before and during estrogen therapy (F = 0.8, p = NS); PeriMW showed higher basal NE levels both before and during estrogen therapy than PreMW (F = 12; p < 0.001). Clonidine administration decreased SBP, DBP and NE levels in PreMW, in PeriMW and in PeriMWE without any difference between the groups (F = 1.2, p = NS; F = 0.5, p = NS and F = 1.3, P = NS respectively). HR decreased significantly after clonidine in PreMW (F = 5.4, p < 0.03) but not in PeriMW before (F = 1.0, p = NS) and during estrogen therapy (F = 0.5, p = NS). Clonidine did not affect plasma E in the three groups studied (F = 2.8, p = NS; F = 2.2, P = NS and F = 0.1, p = NS). The present study demonstrates that increased basal plasma NE levels are present in PeriMW. The cardiovascular and catecholamine response to clonidine in PeriMW both before and during estrogen therapy are similar to those observed in PreMW, suggesting a normal inhibitory alpha-2 receptor pathway.