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Abstract
Several reports suggest that nitric oxide (NO) could play a critical role on synaptic
plasticity related to physical activity improving learning and memory; thus, physical
exercise would have important effects on cerebral health. In order to analyze the
long-term effects of chronic moderate physical training on the morphology and activity
of nitrergic neurons belonging to the cerebral cortex, hippocampus and striatum, and
their relationship with behavioral parameters. Wistar rats were aerobically trained
(AT) up to the age of 18months and compared to sedentary controls (SC). At the end
of the training protocol behavioral parameters were analyzed in an eight-arms radial
maze. Rats were sacrificed by perfusion fixation with 4% paraformaldehyde. Brains
were dissected out and coronal sections containing the three mentioned areas were
obtained. The neurons expressing nitric oxide synthase (NOS) were stained using the
technique of NADPH-diaphorase (NADPH-d) and their morphological and densitometric
parameters were quantified by image analysis. Afterwards, the isoforms of NOS were
determined by immunofluorescence. Results revealed AT rats learned faster, performed
less mistakes and were more successful than SC rats in the maze. The nitrergic neurons
of the cerebral cortex were larger and they had an increased number of dendrites.
The NADPH-d reactivity in the cortex and striatum was upregulated. Colocalization
was significant for the neuronal nitric oxide synthase (nNOS), in both groups. In
conclusion, moderate and chronic exercise had a positive effect on cognitive performance
and anxiety related behavior. An upregulation of the nitrergic system was detected
in AT rats and this fact could be involved in this beneficial action on the aged subjects.