Differential expression of D-1A and D-1B dopamine receptor mRNAs in the developing avian retina

In the chick retina, the D1 dopaminergic system differentiates very early, as shown by receptor-mediated increases in intracellular cyclic AMP concent ration and the presence of [H-3]SCH23390-specific binding sites, Here, we c haracterized, by RT-PCR, the expression of defined D1 receptor subtypes D-1 A, D-1B, and D-1D during the development of the chick retina. Total RNA was extracted from retinas of 6-day-old embryos (E6) to I-day-old hatched chic kens and reverse-transcribed. The resulting cDNA was amplified using D-1A-, D-1B-, or D-1D-specific primers, and the PCR-amplified products were analy zed by electrophoresis. The fragment corresponding to D-1A receptor was det ected in developing retina as early as E7, whereas the fragment correspondi ng to D-1B was observed starting around E10, No PCR product corresponding t o D-1D was observed in the retina, although it was detected in chick brain. As synaptogenesis in chick retina begins after E11 and [H-3]SCH 23390 D1 b inding sites increase after this stage, the present results show that expre ssion of D-1B receptor increases during synaptogenesis, whereas D-1A is the receptor subtype associated with the D1-like actions of dopamine early in retina development.