Objectives To determine the expression of fibroblast growth factor (FGF) on olfactory bulb in rats and its relation with senile hyposmia, and to discuss the effects of rhidosin on expression of FGF on olfactory bulb in senile rats and its significance Methods Four groups of rats, ie, young group, senile group, rhidosin group, and physiological saline control group were used in this study After the removal of the heads of these rats, olfactory mucosa and olfactory bulbs were immediately fixed with neutral formalin, followed with paraffin embedding, serial sectioning, immunohistochemical staining and light microscopic observation Results The positive expression rate of FGF on olfactory bulb in young group was significantly higher than that in senile group (P<0 01) The positive expression rate of FGF on olfactory bulb in rhidosin group was significantly higher than that in physiological saline control group (P<0 01) No positive expression of FGF on olfactory mucosa was observed in these four groups Conclusion These results suggest that the expression of FGF on olfactory bulb gradually decline with aging The decrease of expression of FGF on olfactory bulb may play a key role in the occurrence of senile hyposmia Rhidosin can increase the expression of FGF on olfactory bulbs in senile rats and this may be one of the mechanisms by which rhidosin promotes the growth of olfactory cells and inhibits aging effects on the olfactory system Objectives To determine the expression of fibroblast growth factor (FGF) on olfactory bulb in rats and its relation with senile hyposmia, and to discuss the effects of rhidosin on expression of FGF on olfactory bulb in senile rats and its significance Methods Four groups of rats, Ie, young group, senile group, rhidosin group, and physiological saline control group were used in this study After the removal of the heads of these rats, olfactory mucosa and olfactory bulbs were immediately fixed with neutral formalin, followed with paraffin embedding, serial sectioning , immunohistochemical staining and light microscopic observation Results The positive expression rate of FGF on olfactory bulb in young group was significantly higher than that in senile group (P<0 01) The positive expression rate of FGF on olfactory bulb in rhidosin group was significantly higher than That in physiological saline control group (P<0 01) No positive expression of FGF on olfactory mucosa was obser Ved in these four groups conclude these rates suggest that the expression of FGF on olfactory bulk gradual decline with aging The decrease of expression of FGF on olfactory bulb may play a key role in the occurrence of senile hyposmia Rhidosin can increase the expression of FGF on olfactory Bulbs in senile rats and this may be one of the mechanisms by which rhidosin promotes the growth of olfactory cells and inhibits aging effects on the olfactory system