We have recently shown that estrogen negatively modulates the hypotensive effect of clonidine (mixed ₂-/I₁-receptor agonist) in female rats and implicates the cardiovascular autonomic control in this interaction. The present study investigated whether this effect of estrogen involves interaction with ₂- and/or I₁-receptors. Changes evoked by a single i.p. injection of rilmenidine (600 µg/kg) or -methyldopa (100 mg/kg), selective I₁- and ₂-receptor agonists, respectively, in blood pressure, hemodynamic variability and locomotor activity were assessed in radiotelemetered sham-operated and ovariectomized (OVX) Sprague-Dawley female rats with (OVXE2) or without 12-week estrogen replacement. Three time-domain indices of hemodynamic variability were employed: (i) the standard deviation of mean arterial pressure (SDMAP) as a measure of blood pressure variability, and (ii) the standard deviation of beat-to-beat intervals (SDRR) and the root mean square of successive differences in R-R intervals (rMSSD) as measures of heart rate variability. In sham-operated rats, rilmenidine or -methyldopa elicited similar hypotension that lasted at least 5 hours and was associated with reductions in SDMAP. SDRR was reduced only by -methyldopa. OVX significantly enhanced the hypotensive response to -methyldopa in contrast to no effect on rilmenidine hypotension. The enhanced -methyldopa hypotension in OVX rats was paralleled with further reduction in SDRR and a reduced locomotor activity. Estrogen replacement (17-estradiol subcutaneous pellet, 14.2 µg/day, 12 weeks) of OVX rats restored the hemodynamic and locomotor effects of -methyldopa to sham-operated levels. These findings suggest that estrogen downregulates ₂- but not I₁-receptor-mediated hypotension and highlight a role for the cardiac autonomic control in -methyldopa-estrogen interaction.