Background: Some reports suggest that the synthesis of nitric oxide (NO) may be regulated by sex hormones; it is not yet fully understood, how these hormones interact with the brain nitrergic system in the regulation of cardiovascular functions. The purpose of the present study was to investigate the effect of ovariectomy on cardiovascular functions under baseline conditions and during stimulation or blockade of the central nitrergic system in the regulation of cardiovascular functions in conscious female rats.
Material and methods: One group of animals was subjected to ovariectomy; the other was sham-operated and served as control. Data on mean arterial pressure (MAP) and heart rate (HR) were collected starting from one week after the surgery for four weeks. Subsequently an intracerebroventricular cannula (ICV) and an arterial catheter were implanted in both groups. One week after the ICV surgery, S-nitrosopenicyllamine (SNAP) or NG-nitro-L-arginine (L-NNA) was administered by ICV injection.
Results: A transient decrease in the MAP was observed two weeks after surgery in the ovariectomized rats, but not in those who were sham-operated. Ovariectomy did not produce any significant changes in the resting MAP and HR. The ICV injection of SNAP or L-NNA did not influence blood pressure either in ovariectomized or in sham-operated rats.
Conclusion: The results indicate that the ovaries in rats may produce a factor which tends to maintain blood pressure at a higher level. The brain nitrergic system does not appear to play an essential role in regulating resting blood pressure in female Wistar rats.

Keywords: Nitric Oxide, Estrogens