Regional quantification of dopamine transporter mRNA in rat brain using a ribonuclease protection assay

We describe the regional distribution of dopamine transporter (DAT) mRNA in selected regions of rat brain using a highly sensitive and specific nuclease protection assay. This method determines the absolute quantity of mRNA expressed in the brain regions surveyed. DAT mRNA level varied widely between brain regions, and was detected only in cell body regions of the major dopaminergic pathways. Highest expression was seen in substantia nigra/ventral tegmentum (SN/VTA). Lower but detectable expression of a protected mRNA of the expected size was observed within hypothalamus. Expression could not be detected by this method in other brain regions studied. Our results indicate that this method is sufficiently sensitive to allow study of mRNA expression in individual animals.