The specificity of angiotensin II receptor binding in rat brain |
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Authors: | Francis E. Cole Howard L. Blakesley Karen A Graci Edward D. Frohlich Allan A. MacPhee |
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Affiliation: | aDivision of Research, Alton Ochsner Medical Foundation, New Orleans, LA 70121, USA |
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Abstract: | 125I-angiotensin II (125I-AII) binding was examined in the hypothalamic-thalamic-septal-midbrain (HTSM) region of HLA-Wistar rats in the presence of CNS-active agents. Angiotensin I, II, and III and saralasin competed for 125 I-AII binding, whereas structurally unrelated peptides such as arginine and lysine vasopressin, oxytocin, LHRH, TRH, bradykinin, and substance P did not. In contrast, ACTH and neurotensin exhibited a weak, dose-dependent competition for 125 I-AII binding. The relative potencies of AII, AI, neurotensin and ACTH were 100:1:0.1:0.05, respectively. Neurotensin and ACTH competition was not additive with AII suggesting interaction at shared binding sites. Most importantly, a wide variety of other CNS active agents such as methyldopa, naloxone, catecholamines, clondidine, and reserpine, failed to inhibit 125 I-AII binding, thus further defining the specificity of the CNS AII receptor. |
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Keywords: | Angiotensin II Receptor specificity CNS Rat ACTH Neurotensin |
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