IMMUNOLOCALIZATION OF BCL-X(L S) IN THE CENTRAL-NERVOUS-SYSTEM OF NEONATAL AND ADULT-RATS/

A polyclonal antibody raised against a peptide corresponding to the (2 -19) amino-terminal sequence of the Bcl-x(L/S) protein was used to loc alize Bcl-x immunostaining in the central nervous system of rats at va rious postnatal ages. Whereas Bcl-x immunostaining was present in virt ually all neurons of young animals (4 days postnatal), this staining b ecame progressively restricted during the course of postnatal developm ent. In adults, Bcl-x immunostaining was particularly strong in certai n neurons present in a few hypothalamic nuclei, such as the supraoptic or the arcuate nuclei. Moderate staining was observed in some discret e brain regions, such as the olfactory bulb, the hippocampus, some cat echolaminergic nuclei of the brainstem, and the cerebellum. Strong Bcl -x immunostaining was also exhibited in axon-like fibers located in th e pyriform cortex, the median eminence, the dorsal medulla oblongata, and spinal cord. Bcl-x immunostaining was also present in astrocytes s cattered throughout the white matter in the brain and the spinal cord, but was absent from those located in gray matter. Staining was partic ularly strongly expressed in reactive astrocytes densely packed along the borders of a central lesion or surrounding them, and in a large nu mber of reactive astrocytes detected at a distance from the lesion. Ou r data suggest that, in addition to the possible stimulating effects o n cell survival generally ascribed to Bcl-x, its maintained expression throughout adulthood or its re-expression following injury characteri zes those neuronal or non-neuronal cells of the adult central nervous system that synthesize a range of molecules enabling them to adapt rap idly and successfully to a changing environment.