NO synthase and free radical generation in brain regions of old rats: correlations with individual behaviour.

We have investigated the activity of NO synthase (NOS) and generation of free radicals (FRG) in selected brain regions of old male Wistar rats. Using the emotional resonance test, two groups of rats were selected for the experiment: passive, preferring dark space and active, preferring light space. Highest NOS activity and FRG were seen in cerebellum. As a rule, NOS activity was lower and FRG higher in the respective brain regions of active rats than in passive rats. Positive linear inter-regional cross-correlations of NOS activity as well as of FRG were found. When all rats were assessed as one group, negative correlations between NOS and FRG in cerebral cortex were revealed.