Identification of angiotensin IV binding sites in the mouse brain by a fluorescent binding study

In the brain the renin-angiotensin system has been implicated in the regulation of the cardiovascular system as well as of regulation of reproductive hormones, water balance and behavior. Angiotensin II (Ang II) binds to two distinct receptors called AT1 and AT2. Recently a binding site has been discovered which selectively binds a fragment of Ang II. This biologically active Ang II 3-8 fragment is referred to as angiotensin IV (Ang IV) and has been reported to participate in memory acquisition and recall as well as in the regulation of blood flow, neurite outgrowth, angiogenesis and kidney function. The distribution of binding sites for Ang IV within the mouse brain is unknown. Using a nonradioactive binding assay with a fluorescence-coupled Ang IV, we were able to demonstrate specific Ang IV binding sites in the forebrain of mice, in particular in the cortex, the hippocampus, the amygdala, the thalamus and the hypothalamus.