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.

Keywords: Purkinje cells, AT₂ receptors, Cerebellum development, Zebrin II, Molecular markers