Developmental, Circadian and Aging Aspects of Dopamine, Norepinephrine and 5-HT in Rat Brain Regions

Changes along the scales of 24 hours and of development and aging in the concentration of 3 monoamines—dopamine (DA), norepinephrine (NE) and 5-hydroxytryptamine (5-HT)—were studied concomitantly in different brain areas of the male Wistar rat. A circadian time effect was validated by an analysis of variance with a P≤.05 for all 3 monoamines; point-and-interval estimates of rhythm parameters were obtained by cosinor methods. By 3 months of age, a circadian rhythm was apparent for all variables and brain areas and was demonstrable up to the age of 2 years. The relative abundance of monoamines in different brain areas differed drastically, but the relative peaks and troughs of DA, NE and 5-HT in different parts of the brain occurred in rather consistent segments of the circadian period.