THE EXPRESSION OF B-50 GAP-43 AND GFAP AFTER BILATERAL OLFACTORY BULBECTOMY IN RATS/

In the present study we investigated the effect of a two-stage bilater al lesion of the olfactory bulb (OB) in rats on the regeneration abili ty of peripheral olfactory neurons and their reinnervation capacity in the spared OB. The outgrowth of newly-generated olfactory axons as we ll as the maturation of their terminal synaptic field was detected by immunohistochemistry of the growth-associated phosphoprotein B-50/GAP- 43. In addition, the glial response to the surgery was monitored by an immunohistochemical marker for astrocytes, glial fibrillary acidic pr otein (GFAP). In neonatal rats (P3-P5), the right OB was removed, then three months later the contralateral side was ablated. Six days after the second operation the animals were transcardially perfused. Their brains were embedded in paraplast, serially sectioned and processed fo r histological and immunohistochemical observations. After neonatal OB ablation, homogeneous B-50-immunoreactivity (BIR) was found in the fo rebrain, olfactory axons and ectopic glomeruli localized in the small OB remnant-like structures and in the regenerated neuroepithelium. A s trong GFAP response was revealed in the brain cortex as well as in the newly-formed olfactory axons and glomeruli-like structures of the OB remnants. After adult OB ablation strong BIR was observed in olfactory axons, while remaining glomerular structures were only faintly staine d. The neuroepithelium revealed signs of massive degenerative processe s with a substantial decrease in BIR. The GFAP-positive astrocytes wer e scattered throughout the entire OB remnant and were prominent in the glomeruli-like structures and adjacent frontal cortex. In the present study, we applied GAP-43 and GFAP immunohistochemistry to characteriz e the responses of individual olfactory components after two-stage olf actory bulbectomy. Furthermore, this model of OB ablation characterize d by two immunohistochemical markers could elucidate certain molecular mechanisms involved in the regeneration and/or plasticity of the olfa ctory system.