Xr. He et al., EFFECTS OF 17-BETA-ESTRADIOL ON SYMPATHETIC ACTIVITY AND PRESSOR-RESPONSE TO PHENYLEPHRINE IN OVARIECTOMIZED RATS, American journal of physiology. Regulatory, integrative and comparative physiology, 44(4), 1998, pp. 1202-1208
The effects of 17 beta-estradiol (E-2) on sympathetic activity were ex
amined in conscious unrestrained ovariectomized rats, instrumented und
er methohexital anesthesia to record mean arterial pressure (MABP), he
art rate (HR), renal nerve activity (RNA), and splanchnic nerve activi
ty (SNA) 1 day before the experiment. Injection of E-2 (150 mu g/kg iv
) caused reductions (P < 0.01) in RNA(29 +/- 6%), SNA (25 +/- 2%), and
HR (26 +/- 5 beats/min) within 20 min, but MABP remained unchanged. N
inety minutes after intravenous injection of E-2 or vehicle, intraveno
us infusion of phenylephrine (PE; 6.2 mu g.min(-1).kg(-1)) induced sim
ilar increases in MABP and decreases in HR, RNA, and SNA in both group
s. By contrast, in rats chronically treated with E-2, the presser resp
onse to PE was smaller (P < 0.01; 22 +/- 5 mmHg) than in vehicle-treat
ed rats (40 +/- 4 mmHg). The changes in HR, RNA, and SNA were similar
in both groups, but the ratios of changes in HR and SNA to MABP, an in
dex of baroreflex sensitivity, were greater in the E-2-treated rats. T
hese findings suggest that E-2 can act centrally to modulate sympathet
ic function and thereby participate in cardiovascular regulation.