Expression of Angiotensin Type 1A Receptors in C1 Neurons Restores the Sympathoexcitation to Angiotensin in the Rostral Ventrolateral Medulla of Angiotensin Type 1A Knockout Mice

Abstract

In adult mice we determined whether expression of angiotensin II (Ang II) type 1A receptors (AT(1A)Rs) in C1 neurons mediates the excitation of the rostral ventrolateral medulla (RVLM) by Ang II. Blood pressure, heart rate, and sympathetic nerve activity were measured in anesthetized, artificially ventilated wild-type (n=15) and AT(1A)R knockout (AT(1A)(-/-); n=9) mice. Microinjection of Ang II (50 nL of 0.1 to 1.0 mmol/L) into the RVLM induced a dose-related, sympathetically mediated pressor response (maximum of 17+/-2 mm Hg) in wild-type mice. These microinjections had no effect in AT(1A)(-/-) mice. Endogenous AT(1)Rs occur on catecholaminergic C1 neurons in the RVLM. We induced AT(1A)R or..