Age-related changes in the metabolism of neurotransmitters in rat striatum: a microdialysis study.

Rats from one month to 22 months of age were subjected to in vivo brain microdialysis under a free-moving condition. The 3,4-dihydroxyphenylacetic acid level in the striatum reached a maximum at 3 months old. However, both basal and potassium-induced dopamine release were maximal at 1.5 months, which represents sexual maturation (puberty). The inhibitory effect of monoamine oxidase (MAO) activity by pargyline was maximal at 1.5 months. The delayed maximum level of the metabolites may be due to different age-related changes in MAO-A and MAO-B. From these results, it is suggested that in the rat striatum, the release of dopamine is maximal at the age of sexual maturation, and that the whole synaptic function of the dopaminergic neurons is at its highest during late adolescence.