Abstract
Previously it has been shown that a sexual dimorphism exists in cardiovascular regulation such that females tend to exhibit lower arterial pressure and greater vascular conductance compared with males both at rest and during exercise conditions. Previous studies also indicate that arterial baroreflexes may contribute to the observed sexspecific differences in cardiovascular function. PURPOSE: To test the hypothesis that intact baroreceptor function is necessary for expression of the sexual dimorphism related to reduced arterial pressure and raised vascular conductance seen in female versus male rats. METHODS: Mean arterial pressure (MAP, femoral artery radiotelemetry or tail artery catheter), hind body blood flow (TAQ; terminal aortic flow probe), vascular conductance (VC; TAQ/MAP) and heart rate (HR) were obtained in male (n=14) and female (n=12) Sprague-Dawley rats at rest and during treadmill locomotion at various speeds (5-25 m/min). Of these rats, 7 M and 7 F completed this protocol with intact baroreceptor function and 7 M and 5 F were assessed following bilateral sinoatrial denervation (SAD). RESULTS: Regression analysis revealed that across all trials in rats with intact baroreceptor function, being female was associated with lower MAP, greater VC, and greater TAQ (regression coefficients −9 mmHg, +0.06 conductance units, +5.2 ml/min/kg hind body weight, respectively; all p<0.05). SAD reversed these associations in female rats and was associated with a greater MAP but lower TAQ and VC (regression coefficients +10 mmHg, MAP; −0.11 conductance units, VC; −10.4 ml/min/hind body weight, TAQ; all p<0.05); SAD had little influence on the cardiovascular responses to treadmill locomotion in male rats. CONCLUSION: These results indicate that intact baroreceptor function is essential for expression of decreased MAP and greater VC seen in female rats, whereas the contribution of baroreceptor function to the cardiovascular responses in male rats during treadmill locomotion is minimal. Taken together, this data strongly suggests that the sex-specific differences in cardiovascular regulation are dependent upon intact baroreceptor function. Support: HL46314, DK7690-14
Published Version
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