Monoamine oxidase in brain maturation: a histochemical study during posthatching development in altricial birds

Monoamine oxidase was studied histochemically in the brain of three altricial birds, domestic pigeon house swift and house sparrow, during posthatching development. It was found that there was a steady increase in the activity of the enzyme in all areas of the brain of the three birds. The medulla and thalamus showed adult pattern of maturation by 15-20 days in sparrow while the optic lobes and cerebellum did so by 25 days in the former and 11 days in the latter. The cerebral hemispheres showed this by 25-30 days in pigeon and swift and 14 days in sparrow. The hind brain regions showed maximum activity followed by optic lobes, cortex, basal ganglia and cerebellum. The development of the enzyme activity coincided with myelination, in the different areas, as well as with the development of other mitochondrial enzymes. The study indicates that the maturation of the monoaminergic neurotransmitter systems occurs by 30 days in pigeon and swift, while it takes only about half that time i.e., 14 days, in sparrow.