Purkinje cells express Angiotensin II AT2 receptors at different developmental stages

Abstract

Angiotensin II (Ang II) binds and activates two major receptors subtypes, namely AT1 and AT2. In the fetus, AT2 receptors predominate in all tissues and decline shortly after birth, being restricted to a few organs including brain. Interpretation of the function of Ang II in the cerebellum requires a thorough understanding of the localization of Ang II receptors. The aim of the present paper is to evaluate the localization of Ang II AT2 receptors in the Purkinje cell (PC) layer during development. By binding autoradiography, a clear complementary pattern of AT1 and AT2 binding labeled by [125I] Ang II was observed in young rats within the cerebellar cortex. This pattern was present at the stages P8 and P15, but not at P30 and P60, where AT2 binding appears low and superimposed with AT1 binding. We demonstrate that AT2 antibodies recognized postmitotic Purkinje cells, labeling the somata of these cells at all the stages studied, from P8 to P60, suggesting that PCs express these receptors from early stages of development until adulthood. In P8 and P15 animals, we observed a clear correspondence between immunolabeling and the well-defined layer observed by binding autoradiography. Confocal analysis allowed us to discard the co-localization of AT2 receptors with glial fibrillary acidic protein (GFAP), a glial marker. Double immunolabeling allowed us to demonstrate the co-localization of Ang II AT2 receptors with zebrin II, a specific PC marker. Since PCs are the sole output signal from the cerebellar cortex and considering the role of cerebellum in movement control, the specific receptor localization suggests a potential role for Ang II AT2 receptors in the cerebellar function.