Immunohistochemical mapping of angiotensin type 2 (AT 2) receptors in rat brain

Abstract

Recently developed antisera selective for angiotensin Type 2 (AT 2) receptors were use to localize AT 2 receptors in rat brain by immunohistochemistry. While the results from these experiments were largely consistent with previous autoradiographic and radioligand binding analyses of AT 2 receptor populations in brain, there were also some notable differences in the distribution of immunoreactivity. More specifically, in agreement with previous studies, AT 2 antisera detected apparent receptor populations in the locus coeruleus and the bed nucleus of the accessory olfactory tract, whereas AT 2 receptor-immunoreactivity in the cerebellum was primarily associated with the Purkinje cell layer and the deep cerebellar nuclei rather than the molecular layer as has been previously reported in autoradiographic studies. Other regions with prominent immune-staining included all subfields of the hippocampus, which had been previously reported to contain exclusively AT 1 receptors. Limbic structures such as the amygdala, thalamic areas such as the rhomboid thalamic nucleus, the paraventricular thalamic nucleus, hypothalamic areas such as the paraventricular hypothalamic nucleus, and the supraoptic nucleus also exhibited prominent AT 2-immunoreactivity. In the paraventricular hypothalamic nucleus, AT 2 receptor staining appeared to be associated primarily with the magnocellular neurons. In all regions examined, AT 2 receptor immunoreactivity was associated with the cytoplasm and cell membrane and was not localized within the nucleus. Collectively, these results confirm and extend the neuroanatomical resolution of previous autoradiographic studies as well as identify new AT 2 receptor populations in rat brain.