Intranasal angiotensin II directly influences central nervous regulation of blood pressure

Intranasal administration of some peptides has been shown to directly influence central nervous functions, thus pointing to a nose-brain pathway for these substances in humans. The present study investigated whether intranasal administration of angiotensin II (ANG II) affects central nervous functions of cardiovascular control in a different way from intravenously administered ANG II. In a balanced cross-over design 12 healthy men were treated with ANG II intravenously (2.5 μg), ANG II intranasally (400 μg), and placebo. Angiotensin II, vasopressin, norepinephrine, and epinephrine plasma levels were assessed every 10 min; blood pressure, heart rate, and systemic vascular resistance were measured by a Dinamap, and by continuous, noninvasive body plethysmography. Also, feelings of activation and mood were measured. Intranasal and intravenous administration invoked equivalent increases in plasma levels of ANG II, and induced an acute rise in blood pressure of comparable size and duration. However, subsequent blood pressure profiles differed dependent on intravenous and intranasal ANG II administration; after intravenous ANG II administration blood pressure remained enhanced at an intermediate level, but it returned to normal or even decreased below normal levels after intranasal ANG II administration. Intranasal ANG II also counteracted the decrease in norepinephrine levels observed after intravenous administration of ANG II. Intranasal but not intravenous ANG II enhanced plasma concentrations of vasopressin. This diverging pattern of effects bears similarities with effects of intracerebroventricular administration of ANG II in animals, suggesting that the effects after intranasal administration reflect a direct central nervous action of ANG II.