ANGIOTENSIN-II BINDING IN AREA POSTREMA AND NUCLEUS-TRACTUS-SOLITARIUS OF SHR AND WKY RATS

The distribution of angiotensin II (AII) binding sites in the area pos trema (AP) and adjacent nucleus tractus solitarius (NTS) was compared in spontaneously hypertensive (SHR) rats and normotensive Wistar-Kyoto (WKY) rats. I-125[Saralasin1-Isoleucine8]-Angiotensin II (I-125[SI]-A II) binding density was quantitated from autoradiographic images by co mputer-assisted image analysis. Seventeen 30 mum serial coronal sectio ns inclusive of the entire AP were analyzed as either individual secti ons or as groups of sections designated as caudal, middle, or rostral area postrema regions. I-125[SI]-AII binding density was greatest in c audal AP and declined progressively in the rostral direction in both s trains; however, binding density in SHR was significantly higher than in WKY rats at each level of the AP analyzed. I-125[SI]-AII binding in the entire area postrema was approximately 46% higher in SHR rats. In the NTS, however, there were no differences in binding density betwee n strains. At the middle level of the AP, I-125[SI]-AII binding was hi ghest in the ventral midline and lowest in the dorsolateral region. In the NTS, the highest I-125[SI]-AII binding density was found in the p ars commissuralis and pars medialis. In conclusion a) I-125[SI]-AII bi nding density was nonhomogeneus in the AP and NTS of both strains, b) qualitatively similar patterns of nonhomogeneity of binding in the AP and NTS were noted in both strains: however, c) the SHR strain consist ently had higher density All binding than WKY in AP, but not in NTS.