Dopamine release during stress in the prefrontal cortex of the rat decreases with age

The effects of aging on the stress-induced increases of dopamine and the dopamine metabolites 3,4-dihydroxyphenylaectic acid (DOPAC) and homovalinic acid (HVA) in the medial prefrontal cortex of the awake rat were investigated using microdialysis. In young rats (2-3 months) handling stress produced an increase of dopamine by 205% and of the dopamine metabolites DOPAC by 120% and HVA by 155% of baseline as maximal increases. In middle-aged rats (14 months) the increase of dopamine was significantly lower than in young rats (155% of baseline), while in aged rats (30 months) stress produced no significant increases of dopamine in the prefrontal cortex. These results indicate that the effects of stress on dopamine release in the medial prefrontal cortex of the rat diminishes during the normal process of aging.