Received January 11, 2008
Revised February 7, 2008
Accepted after revision March 13, 2008

¹ Wake Forest University School of Medicine
² Wake Forest University

^* To whom correspondence should be addressed. E-mail: ddiz{at}wfubmc.edu.

	Abstract

Injections of the Ang-(1-7) antagonist [D-Ala7]-Ang-(1-7) into the nucleus of the solitary tract (nTS) of Sprague-Dawley rats reduce baroreceptor reflex sensitivity (BRS) for control of heart rate by ~40%, whereas injections of the AT1 antagonist candesartan increase BRS by 40% when reflex bradycardia is assessed. The enzyme angiotensin converting enzyme 2 (ACE2) is known to convert angiotensin (Ang) II to Ang-(1-7). We report that ACE2 activity, as well as ACE and neprilysin activities, are present in plasma membrane fractions of the dorsomedial medulla of Sprague-Dawley (SD) rats. Moreover, we show that BRS for reflex bradycardia is attenuated (1.16 +/- 0.29 msec/mm Hg before versus 0.33 +/- 0.11 msec/mm Hg; p < 0.05; n = 8) 30 - 60 minutes following injection of the selective ACE2 inhibitor, MLN4760 (12 pmol/120 nL), into the nucleus of the solitary tract (nTS). These findings support the concept that within the nTS, local synthesis of Ang-(1-7) from Ang II is required for normal sensitivity for the baroreflex control of heart rate to increases in arterial pressure.

Key Words: Angiotensin, Arterial baroreflex, Enzyme

This article has been cited by other articles:

				P. E. Gallagher, C. M. Ferrario, and E. A. Tallant MAP kinase/phosphatase pathway mediates the regulation of ACE2 by angiotensin peptides Am J Physiol Cell Physiol, November 1, 2008; 295(5): C1169 - C1174. [Abstract] [Full Text] [PDF]

				M. K. Raizada and J. F. R. Paton Recent advances in the renin-angiotensin system: angiotensin-converting enzyme 2 and (pro)renin receptor Exp Physiol, May 1, 2008; 93(5): 517 - 518. [Full Text] [PDF]