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In vitro receptor autoradiography, using the radiolabeled angiotensin II (Ang II) antagonist ¹²⁵I-sar¹, ile⁸ Ang II (^∣25I-SI Ang II; 250 pM) in the absence or presence of 1 µM Ang II, was used to identify Ang II receptor binding sites in the preoptic-anterior hypothalamic (POAH) brain region of cycling female rats. A nucleus within this region, lateral to the organum vasculosum of the lamina terminalis and ventral to the anterior commissure, displayed a discrete locus of ¹²⁵I-SI Ang II binding sites (385 fmol/g tissue). This nucleus, which corresponds to the area of the POAH from which Ang II is most effective at eliciting luteinizing hormone release, has been identified as the ventral portion of the bed nucleus of the stria terminalis (BSTV) by the rat brain atlas of Paxinos and Watson. The selective nonpeptidic Ang II_α receptor antagonist Dup 753 completely inhibited the binding of ¹²⁵I-SI Ang II to the BSTV and other hypothalamic nuclei, suggesting that these receptors are of the Ang II_α subtype.

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