Autoradiographic localization of angiotensin II receptors in developing rat cerebellum and brainstem

The role of Angiotensin II (Ang II) as a growth promoting or modulating fac tor has recently become a field of intensive research. A central issue in d evelopmental neurobiology is the understanding of mechanisms governing the formation of spatially ordered connections. In this study, we show the loca lization of Ang II receptor subtypes by autoradiography in 2-week-old rat h indbrains confronting these data with membrane binding assays. Competition studies done on membrane preparations evidence no major changes on the rela tive affinities for both receptor subtypes between 2-week-old and adult rat tissues. By autoradiography, we found that all the areas (1-10) of the 2-w eek-old cerebellum showed both receptor subtypes present in complementary a djacent layers. Areas expressing a high level of AT(2) receptors follow: in ferior colicullus (IC), dorso tegmental nucleus, central (DTgC), subcoerule us, alpha, sensory root of the trigeminal nerve, principal sensory root tri geminal nucleus (Pr5, Pr5VL) supragenual nucleus, genu facial nerve, facial nucleus, cerebelar peduncles, vestibular and lateral nuclei. Spinal trigem inal, (oral) and Raphe nuclei express AT(1) receptor subtype. The high leve l of Ang II AT(2) receptors present in the cerebellar peduncles might have a meaning on the establishment of the olivo-cerebellar connection. The high expression of Ang II AT(2) receptors on 2-week-old rat hindbrains, a criti cal age on development, as well as its disappearance in the adult, strongly suggests a probable role of these receptors in cell migration and neuronal synaptogenesis. (C) 2001 Elsevier Science B.V. All rights reserved.