MESSENGER-RNA AND PROTEIN EXPRESSION OF BASIC FIBROBLAST GROWTH-FACTOR RECEPTOR AFTER CORTICAL ABLATION

In a previous report we demonstrated that basic fibroblast growth factor (bFGF), as a multipotent neurotrophic factor, could prevent retrograde degeneration of the thalamic neurons after ablation of the somatosensory cortex. To elucidate the mechanism of this bFGF action, we examined changes in FGF receptor (FGFR) mRNA (flg) expression with in situ hybridization. The FGF receptor protein was detected with the immunoblotting method. The FGFR mRNA expression was found to be diffusely increased in the affected cortex. Microscopic observation indicated that FGFR mRNA was expressed in several types of cortical cells including neurons and non-neuronal cells. This increase could be observed as early as 6 hours after surgery and lasted for 48 hours. In the thalamus, however no change in FGFR mRNA signals was observed. Western blotting detected a protein immunoreactive to anti-FGFR antibody. Samples from the periablated cortex showed an increase in FGFR protein. Samples from the thalamus, however, showed no difference in FGFR protein level between the lesion side and the contralateral side. Application of exogenous bFGF in Gelfoam to the cortical ablation cavity did not show any effect on the gene expression or protein level of FGFR. These results suggest that FGFR is diffusely induced throughout the injured cortex in the early phase after injury and that bFGF may play an important role after injury. Topically applied bFGF might thus modulate cellular responses in the cortex and have a neurotrophic effect on the affected thalamic neurons.