Ontogenetic expression and splicing of estrogen receptor-alpha and beta mRNA in the rat midbrain

Several studies have shown that estrogen is important for the differentiation of midbrain dopaminergic neurons. This is supported by the previous demonstration of estrogen synthesis in the perinatal ventral midbrain. The present study attempts to characterize the expression pattern of nuclear estrogen receptors (ER-alpha/beta) mRNAs in the ventral rat midbrain during development. By applying primers specific for the hormone-binding domain, ER-alpha mRNA was detected from embryonic day (E) 14 until postnatal day (P) 20, whereas considerable levels of ER-beta mRNA were found from P3 to P20. In contrast, primers spanning the DNA-binding domain demonstrated the presence of transcripts for ER-alpha as well as ER-beta after birth. These findings indicate that both ERs are expressed in the developing midbrain. The presence of ER-alpha transcripts devoid of the DNA-binding region is discussed in the context of 'non-genomic' estrogen signaling possibly by membrane receptors.