Immunocytochemical expression of dopamine-related transcription factors Pitx3 and Nurr1 in prenatally stressed adult rats.

Rats exposed to different types of stress during the last week of pregnancy produce offspring that show severe anomalies in neural development and brain morphology. We have previously reported that prenatal stress (PS) induced by immobilization increases D2-type dopamine (DA) receptor levels in the adult offspring, with a concomitant reduction in DA release in prefrontal cortex after amphetamine stimulation. Recently, two transcription factors, Nurr1 and Pitx3, have been identified that are expressed at critical moments of DA neuron differentiation. Their genetic expression is activated immediately after these neuron determinations and maintained through adult life. Nurr1 regulates several proteins that are required for dopamine synthesis and regulation, and Pitx3 is specifically involved in the terminal differentiation and maintenance of dopamine neurons. By means of an immunocytochemistry approach, we studied the expression of Nurr1 and found an ubiquitous distribution in cerebral cortex, hippocampus, thalamus, amygdala, and midbrain, whereas Pitx3 remains restricted to the mesencephalic DA neurons such as substantia nigra and ventral tegmental area. Our results show that the expression of both Nurr1 and Pitx3 increased in prenatally stressed adult offspring in the ventral tegmental area, whereas no changes were observed in the substantia nigra area. It might be hypothesized that the increase of the specific dopaminergic transcription factors might be a compensatory mechanism to counteract the reduction in dopamine levels previously observed as a consequence of prenatal stress.