Postnatal ontogenesis of dopaminergic and serotoninergic systems in rat caudate nucleus

The development and sex differences of the catecholaminergic and serotoninergic systems were studied in rat caudate nucleus by measuring dopamine, serotonin and their metabolites in male and female pups from birth up to day 30 of life. Dopamine increased regularly during the entire period studied, while its metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), increased sharply only after day 9 of life. At birth, serotonin levels were 50% of the juvenile value; its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), increased greatly after day 6 of life. No difference was observed in male and female neurotransmitter ontogenesis. The results indicated that dopaminergic and serotoninergic systems were not mature in the caudate nucleus at birth. A functional immaturity of enzyme systems involved in neurotransmitter synthesis and/or catabolism is suggested.