This study was designed to investigate the postnatal developmental plasticity of the mesostriatal and mesolimbic
dopamine systems that occurs following perinatal
asphyxia. The time course and patterning of the changes in levels of
tyrosine hydroxylase (TH), and D1 and D2
dopamine receptor (R)
mRNA in the cell body region, substantia nigra and ventral tegmental area (SN/VTA), and projection fields, striatum and limbic regions at the age of 6 and 24 h, and 1 week after
asphyxia were studied with a quantitative reverse transcription polymerase chain reaction method with appropriate internal
cRNA standard. In Caesarean-delivered control rats (Sprague-Dawley), TH, D2R and D1R
mRNA levels showed regional and temporal specificity in both absolute levels and developmental kinetics during the first week of life. TH
mRNA levels were >10-fold higher in SN/VTA than in striatum and limbic regions. Compared to Caesarean delivered controls, severe
asphyxia (15-20 min) induced an increase of TH and D2R
mRNA in SN/VTA 6 h and 1 week after birth. In addition,
asphyxia induced an increase of TH
mRNA in the projection fields, striatum and limbic regions, at 1 week. Perinatal
asphyxia did not appear to exert any effect on D1R
mRNA levels. No differences in any of the parameters were observed between spontaneous- and Caesarean-delivered animals. The present results indicate that perinatal
asphyxia triggers coordinated changes in the expression of TH, and
dopamine receptor mRNA in SN/VTA, striatum and limbic regions. These changes may affect differently
dopamine D2R and D1R expression along development, contributing to long-term neurocircuitry imbalances.