SUBCELLULAR-LOCALIZATION OF THE INOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR, P400, IN THE VESTIBULAR COMPLEX AND DORSAL COCHLEAR NUCLEUS OF THE RAT

The subcellular localization of the inositol 1,4,5-trisphosphate recep tor protein, P-400, was studied in the vestibular complex, an area to which Purkinje cells project, as well as in neurons of the dorsal coch lear nucleus and in ectopic Purkinje cells of adult rat brain. The rec eptor was demonstrated by electron microscopical immunocytochemistry u sing the avidin-biotin peroxidase complex procedure, with the monoclon al antibody 4C11 raised against mouse cerebellar inositol 1,4,5-trisph osphate receptor protein. Immunoreactivity was found in preterminal fi bres and terminal boutons in the nuclei of the vestibular complex, gen erally associated with the subsurface systems and stacks or fragments of smooth endoplasmic reticulum. Ectopic Purkinje cells and cartwheel cells of the dorsal cochlear nucleus also displayed immunoreactivity, but this was much less intense in the latter. The results of the prese nt study suggest that this receptor protein, involved in the release o f Ca2+, is located in sites that enable it to influence the synthesis, transport and release of neurotransmitters.