Effect of Microinfusion of Angiotensin Ⅱ into the RVLM in Rats on the Baroreceptor Reflex Sensitivity
Abstract：Objective: The present study was designed to investigate the effect of microinfusion angiotensin Ⅱ (Ang Ⅱ ),Ang Ⅱ type 1(AT1 )receptor antagonist losartan into the rostral ventrolateral medulla(RVLM)on the baroreceptor reflex sensitivity(BRS)in urethane-anesthetized rats. Methods: Reflex changes in heart rate(HR)were elicited by bolus intravenous injection of phenylephrine before and during RVLM microinfusion of saline(0.5 μl/h), Ang Ⅱ (1.5 nmol/h), losartan (250 nmol/h ), and Ang Ⅱ (1.5 nmol/h)pretreated with microinjection of losartan (50 nmol/0.51 μl) into the RVLM. The average ratio between changes in HR in beats per minute ( beats. min- 1 ) and changes in mean arterial pressure [ MAP, mmHg( 1 Hg = 0.133 kPa) ] was used as an index of BRS. Results: Ang Ⅱ resulted in a significant decrease in the BRS for reflex bradycardia compared with control ( - 2.1 + 0.1 vs - 3.9 + 0.4Ang Ⅱ was almost completely abolished by pretreatment with microinjection of losartan. Conclusion:These results showed that the exogenous Ang Ⅱ in the RVLM produces inhibitory modulation of BRS, which is mediated by AT1 receptor. However,AT1 receptor in the RVLM is not involved in the tonic control of BRS.
Keywords：angiotensin ⅡAT1 receptorbaroreceptor reflexrostral ventralateral medulla
Publication Date：2004-05-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：4( 121-124 )