Estrogen modulation of baroreflex function in conscious mice.

Area of Science:

• Cardiovascular Physiology
• Neuroendocrinology
• Autonomic Neuroscience

Background:

• Estrogen is known to influence autonomic nervous system function.
• Baroreflexes are crucial for maintaining blood pressure homeostasis.
• The role of estrogen in baroreflex regulation requires further elucidation.

Purpose of the Study:

• To investigate the effects of estrogen on baroreflex regulation of heart rate in a conscious mouse model.
• To compare baroreflex responses between male and female mice with and without estradiol replacement.

Main Methods:

• Utilized a conscious mouse model with chronic arterial and venous catheterization.
• Administered phenylephrine (PE), angiotensin II (ANG II), and sodium nitroprusside (SNP) to assess baroreflex responses.
• Compared baroreflex bradycardic and tachycardic responses in male, ovariectomized female mice without estradiol (OvxE-), and ovariectomized female mice with estradiol (OvxE+).

Main Results:

• Estradiol significantly facilitated the baroreflex bradycardic response to PE in female mice (OvxE+ vs. OvxE-).
• Estradiol also significantly enhanced the baroreflex bradycardic response to ANG II in female mice (OvxE+ vs. OvxE-).
• Reflex tachycardic responses to SNP were similar across all groups.
• Male mice showed a significantly blunted baroreflex bradycardic response to ANG II compared to PE, an effect not observed in female mice.

Conclusions:

• Estrogen facilitates baroreflex function in female mice, particularly in response to pressor stimuli.
• The acute blunting of baroreflex regulation of heart rate by ANG II appears to be sex-dependent.
• These findings highlight the significant influence of sex hormones on cardiovascular autonomic control.