Developing brain as an endocrine organ: Secretion of dopamine

This study was aimed to test our hypothesis that the developing brain operates as an endocrine organ before the establishment of the blood–brain barrier (BBB), in rats up to the first postnatal week. Dopamine (DA) was selected as a marker of the brain endocrine activity. The hypothesis was supported by the observations in rats of: (i) the physiological concentration of DA in peripheral blood of fetuses and neonates, before the BBB establishment, and its drop by prepubertal period, after the BBB development; (ii) a drop of the DA concentration in the brain for 54% and in blood for 74% on the 3rd postnatal day after the intraventricular administration of 50 μg of α-methyl-p-tyrosine, an inhibitor of DA synthesis, with no changes in the DA metabolism in peripheral DA-producing organs. Thus, the developing brain is a principal source of circulating DA which is capable of providing an endocrine regulation of peripheral organs and the brain.

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► We tested our hypothesis that the developing brain operates as an endocrine organ.
► Dopamine (DA) was used as a marker of the brain endocrine activity.
► DA was shown to circulate in blood before the development of the blood–brain barrier.
► DA concentration in plasma dropped after the establishment of the blood–brain barrier.
► DA concentration in plasma dropped after an inhibition of DA synthesis in the brain.