Localization of endothelin-A and -B receptors during the postnatal development of rat cerebellum

Abstract.

Intense expression of mRNA of endothelin-B receptor (ET_BR) has been detected in the Bergmann glia of cerebellum by in situ hybridization, but the intracellular localization has not been reported because of the absence of a useful antibody for immunohistochemical investigations. We made polyclonal antibodies against the carboxyl terminus of human ET_BR (420–442) and ET_AR (403–427), and performed light- and electron-microscopic immunohistochemistry of the wild-type and ET_BR-deficient (sl/sl) rat cerebella. Localization of ET_BR during postnatal development was examined by double-staining immunofluorescence using antibodies against ET_BR and S-100β. In the wild-type rats, ET_BR immunoreactivity appeared from postnatal day 5 (P5) and was distributed diffusely in the processes and cell bodies of S-100β-positive glial cells. By P14, ET_BR immunoreactivity was concentrated in the Golgi apparatus of Bergmann glial cell soma and the plasma membrane of its processes. The ET_BR-positive astrocytes in the granular layer decreased in number during P7–14 and had disappeared by week 3. At 3 weeks, ET_BR immunoreactivity was restricted to the Golgi apparatus of Bergmann glia. In the sl/sl rats, ET_BR immunoreactivity was not observed at all. In contrast to ET_BR, ET_AR immunoreactivity appeared transiently in the cytoplasm of all astrocytes (Bergmann glia and astrocytes in the granular layer) in the 9- to 14-day-old wild rats and 7- to 14-day-old sl/sl rats, and disappeared within 3 weeks in both. Granule cells did not express immunoreactivity for ET_BR and ET_AR from the neonatal stage to adulthood. Changes in the intracellular localization of ET_BR and transient expression of ET_AR may be correlated with the changes of glial functions and proliferation during postnatal development of rat cerebellum.