Regional brain monoamine levels and utilization in middle-aged rats

Significant changes in monoamine levels and utilization were noted in certain brain regions of middle-aged Fisher 344 rats when compared with young adult controls. In the prefrontal cortex and septum, 3,4 dihydroxyphenylglycol (MHPG) and the MHPG/norepinephrine (NE) ratio were decreased. The septum also showed increases in dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) but there was a decrease in the DOPAC/DA ratio. The striatum showed an increase in the MPHG/NE ratio and an increase in DOPAC. The hippocampus and thalamus showed an increase in 5-hydroxyindoleacetic acid (5HIAA). This demonstrates that selected neurotransmitter systems in the brain are altered at an early stage of senescence. This could lead to ensuing neurological deficits.