Ontogenic development of brain asymmetry in dopaminergic neurons.

In the present study the right-left brain asymmetry of central dopamine (DA) systems during postnatal brain development is evaluated. DA and dihydroxyphenylacetic acid (DOPAC) levels increased from neonatal to adult life in both the forebrain and mesencephalon. This increase was not similar in the right and left brain sides. From neonatal life to adulthood a fall was observed in (a) DA percentage in the DA high-brain side in the mesencephalon and (b) DOPAC percentage in the DOPAC high-brain side in both the forebrain and mesencephalon. The percentage of lateralized rats (more than 65% of DA or DOPAC levels in either brain side) also decreased during ontogeny. Thus, biochemical lateralization decreases during ontogeny. The right-left brain correlation for DA level and DA turnover was used to evaluate the inter-hemispheric regulation of dopaminergic systems. The correlation coefficient was near to 0 during postnatal life and around -0.8 during adulthood in both forebrain and mesencephalon. Taken together, these data suggest that the ontogenic decrease of in brain asymmetry for DA or DOPAC levels is related to the postnatal development of an inter-hemispheric regulatory system that control dopaminergic neurons activity.