Novel angiotensin II binding sites in the mesopontine area of the rat brain

Abstract

Angiotensin II (AII) immunoreactivity in the mesopontine area of the rat brain is distributed through several areas where co-localization of AII receptors has not been established. The current in vitro receptor autoradiography study re-examined the distribution of AII binding using 125I-Sar 1, Ile 8-AII ([ 125I]SIAII). When incubations were conducted without sulfhydryl reducing agents, [ 125I]SIAII binding was observed in the locus coeruleus, inferior colliculus, superior colliculus and the central gray in agreement with previous reports. Novel [ 125I]SIAII binding sites were detected in the parabrachial nucleus, pedunculopontine tegmental nucleus and the caudal linear raphe nucleus, corresponding with previously reported localization of AII immunoreactivity in these nuclei. [ 125I]SIAII binding was also found in the paragenual nucleus where the peptide has not been detected. Thus, the observation of novel AII receptors which are sensitive to sulfhydryl reducing agents, resolves several AII-AII receptor mismatches.