Immunocytochemical localization of tubulin and the high molecular weight microtubule-associated protein 2 in Purkinje cell dendrites deprived of climbing fibers.

The modifications in the localization of tubulin and the high molecular weight microtubule-associated protein 2 were studied in the cerebellum after partial denervation. Both proteins were localized in 40 micron sections using monoclonal antibodies against beta-tubulin (clones Tu9B and Tu12) or microtubule-associated protein 2 (clones AP9 and AP13), and polyclonal antisera against alpha- and beta-tubulin or microtubule-associated protein 2, visualized with the immunoperoxidase method of Sternberger [Sternberger (1979) Immunocytochemistry; Sternberger and Sternberger (1983) Proc. natn. Acad. Sci. U.S.A. 80 6126-6130] or a biotin-avidin system. The destruction of the inferior olive was performed in adult male rats by electrocoagulation or by intraperitoneal administration of 3-acetylpyridine. One day after chemical destruction of the inferior olive, anti-microtubule-associated protein 2 staining with either of the monoclonal antibodies or with the polyclonal antiserum was almost identical to that observed in the cerebellum of non-denervated animals. Specific staining was intense in the cell somata and dendrites and absent in myelinated tracts and in parallel fibers. However, 3 days after the lesion anti-microtubule-associated protein 2 staining showed a clear decrease, both in the proximal and the distal portions of thick secondary and tertiary dendritic trunks of the Purkinje cell. The intensity of the staining was also considerably reduced in the fine dendritic ramifications. By 8 days post-lesion, microtubule-associated protein 2 immunoreactivity began to increase, but only in the portions of the dendrites deprived of the climbing fibre; on the contrary, low immunoreactivity was found in the fine dendritic ramifications which are contacted by normal parallel fibers; microtubule-associated protein 2 immunoreactivity increased considerably by 11 days post-lesion, giving a pattern quite similar to that of non-denervated Purkinje cells. The alterations in microtubule-associated protein 2 immunoreactivity were also accompanied by a dramatic decrease in the immunostaining for tubulin, beginning on day-3 post-lesion and lasting until day-15 post-lesion. These changes were observed with either the monoclonal antibodies against beta-tubulin or with the polyclonal antiserum against alpha- and beta-tubulin. The changes in both molecules were also observed in animals in which the inferior olive was destroyed by electrocoagulation, ruling out the possibility of a direct action of 3-acetylpyridine on dendritic microtubular proteins.(ABSTRACT TRUNCATED AT 400 WORDS)