POSTNATAL-DEVELOPMENT OF THE COMPLEXES OF THE ELECTRON-TRANSPORT CHAIN IN SYNAPTIC MITOCHONDRIA FROM RAT-BRAIN

The postnatal development of the complexes of the electron transport c hain in mitochondria isolated from rat brain synaptosomes was investig ated. Synaptosomal brain mitochondria were isolated from rats aged 10- 60 days, and the activities of mitochondrial complex I, complex II-III , complex IV and complex V were measured. There was a significant incr ease in the activity of complex V from day 10 to day 60 post partum, a nd in the activities of complex II-III from day 10 to day 15 and compl ex IV from day 10 to day 21, thereafter the activities of complexes I- III and IV did not change significantly. The activity of complex I did not change significantly during the period 10-60 days post partum. In synaptic mitochondria, complex V activity was higher than in non-syna ptic mitochondria, whereas the activity of complex I was lower than in non-synaptic mitochondria. These data show that the complexes of the respiratory chain within synaptic mitochondria have activities differe nt from those of non-synaptic mitochondria and may have major implicat ions for the relative susceptibility of mitochondria in different brai n cell types to neurotoxins such as MPP(+), hypoxic/ischaemic damage a nd oxidative stress.