Ontogeny of dopamine D2 receptor mRNA in rat brain.

The postnatal development of rat brain dopamine D2 receptor gene expression was investigated in animals 1 day to 1 year old. The level of expression of the striatal D2 mRNA was appreciable at birth (day 1), steadily increased to a maximum at day 28, and showed declines at ages 6 months and one year. The mRNA development profile was similar to that of [3H]spiroperidol binding in striatal membranes except that there was a lack of correlation between mRNA levels and [3H]spiroperidol binding during the early developmental periods. For example, although the mRNA expression at day 1 is about 75% of the 28-day value, the corresponding level of [3H]spiroperidol binding is only 15% of the value observed at day 28. Polymerase chain reaction (PCR) analysis of alternatively spliced forms of D2 receptor mRNA showed that the developmental expression of the two isoforms proceeded in parallel as the ratio of D2L and D2S mRNAs remained more or less constant in different age group of rats. In situ hybridization revealed a differential developmental profile of D2 mRNA for major dopaminergic regions of rat brain such as caudate putamen, nucleus accumbens, olfactory tubercle and substantia nigra.