The changes of nitric oxide, nitric oxide synthase and neuronal apoptosis in the aged rat brain / 中华老年医学杂志

ABSTRACT

Objective To explore the changes of nitric oxide (NO) and nitric oxide synthase (NOS) of the aged rat brain, and the relationship between this change and neuronal apoptosis. Methods Five month old and 30 month old rats were used in the study. NO level and NOS activity were measured by Griess reaction and high presssure liquid chromatography. Neuronal NOS(nNOS) gene and bcl 2 gene were examined by in situ hybradization; nNOS protein level and free calcium level in synaptosome were determined by immunohistochemical method and Fura 2 fluorescence probe respectively. Apoptosis was observed using terminal transferase marking method. Results NO level and nNOS activity in the brain tissue of aged rats was (2 61?0 10) ?mol/L and (398 22?21 62) fmol?mg -1 ?min -1 , respectively,being significantly higher than that of the young rats(1 54?0 15) ?mol/L and (234 38?16 24)fmol?mg -1 ?min -1 respectively. Also both the nNOS gene transcription and protein expression increased in aged rats while bcl 2 gene expression reduced with aging. Free calcium level in synaptosome of aged and young rats was (485 26?28 48) nmol/L and (372 99?19 20) nmol/L respectively. Apoptosis in brain tissue was observed in aged rats, but not in young ones. Conclusions The increase of NO level in the aged rat brain is due to the increase of nNOS activity which is at least partially determined by the increased gene expression. Abnormal enhancement of NO in the aged rats may cause damage, even death of the brain. As an anti oxidant, bcl 2 gene expression reduced with aging and resulted in the brain tissue more vulnerable to oxidative stress and thus produced more lesions. Therefore, it is a promising method to screen and develop drugs that can be anti apoptotic and anti oxidative, and reduce the formation of pathologic NO to prevent and retard brain aging.