Angiotensin type 1A receptor expression in C1 neurons of the rostral ventrolateral medulla contributes to the development of angiotensin-dependent hypertension.

Chronic low-dose systemic infusion of angiotensin II induces hypertension via activation of the angiotensin II type 1A receptor (AT1AR). Previously, we have demonstrated that expression of the AT1AR on catecholaminergic neurons is necessary for the full development of angiotensin-dependent hypertension. In the present study, we examined the mechanism by which selective deletion of the AT1AR from these cells affects the development of hypertension. We also tested the hypothesis that AT1ARs expressed by catecholaminergic C1 neurons in the rostral ventrolateral medulla play an important role in angiotensin-induced hypertension. A Cre-lox approach was used to delete the AT1AR from all catecholaminergic cells or from C1 neurons selectively. Subcutaneous administration of angiotensin II induced hypertension in all mice, with delayed onset and reduced maximal response in the global AT1AR catecholaminergic knockout mice. The AT1AR catecholaminergic knockout mice had decreased renal fluid and electrolyte retention and urinary noradrenaline excretion. The blood pressure response was reduced only during the second week of angiotensin II infusion in the mice with selective C1 AT1AR deletion, demonstrating that AT1AR expression by C1 neurons plays a moderate role in angiotensin-induced hypertension. The difference in the time course of development of hypertension between the mice with global AT1AR knockout from catecholaminergic cells and the mice with C1 AT1AR deletion suggests that other catecholaminergic neurons are important.