Intravenous estrogen significantly increased vagal efferent activity and baroreflex sensitivity in male rats, an effect blocked by central administration of an estrogen receptor antagonist.
Does peripherally administered estrogen alter central autonomic tone and cardiovascular reflex control in male rats?
Estrogen acts centrally in male rats to enhance baroreflex sensitivity by increasing parasympathetic efferent tone.
The following experiments were conducted to determine if peripherally administered estrogen has an effect on central autonomic tone and whether this change in tone results in an alteration in cardiovascular reflex control. Male Sprague-Dawley rats were anesthetized with thiobutabarbitol sodium (50 mg/kg) and instrumented to record blood pressure, heart rate, and vagal parasympathetic or renal sympathetic efferent nerve activity. Additional rats were instrumented to test the sensitivity of the cardiac baroreflex using intravenous injections of phenylephrine hydrochloride (0.025, 0.05, 0.1 mg/kg) or sodium nitroprusside (0. 0025, 0.005, 0.01 mg/kg) and plotting the cardiovascular responses. Intravenous injection of estrogen (10(-4), 10(-2), and 10(-1) mg/kg) produced a significant increase in vagal efferent activity and in baroreflex sensitivity. The bilateral microinjection of an estrogen receptor antagonist, ICI-182,780 (1 pM, 50 nl/side) into the nucleus ambiguus blocked both the estrogen-induced increase in vagal efferent activity and baroreflex sensitivity. These results demonstrate that in male rats estrogen acts centrally to enhance baroreflex sensitivity by increasing parasympathetic efferent tone.
Saleh et al. (Mon,) reported a other. 17β-estradiol (estrogen) was evaluated on Vagal efferent activity and baroreflex sensitivity. Intravenous estrogen significantly increased vagal efferent activity and baroreflex sensitivity in male rats, an effect blocked by central administration of an estrogen receptor antagonist.